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Improve Any stack usage #1304

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@cdvr1993 cdvr1993 commented Jul 27, 2023

By doing this unsafe approach we are able to save one call to morestack.

Stack usage

SUBQ $0x118, SP // 280 bytes

Benchmark before

goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/normal             18570822                61.33 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-2           20671512                59.85 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-4           20064495                58.73 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-8           19763770                60.18 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal_with_logger                  7673887               157.4 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-2                8318539               143.0 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-4                8584477               139.0 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-8                8203886               147.7 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_new_goroutine                 273378              3873 ns/op             137 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-2               496189              2141 ns/op              72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-4              1000000              1088 ns/op              72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-8              1743856               678.5 ns/op            72 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 15.922s

Benchmark after

goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/normal             15874744                75.15 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-2           16086948                71.64 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-4           16595194                71.02 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-8           16130025                72.98 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal_with_logger                  9092430               130.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-2               10157986               122.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-4                9523335               123.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-8                9183698               128.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine                1250547               883.7 ns/op            73 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-2              2108619               659.3 ns/op            72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-4              2919674               407.9 ns/op            72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-8              4778667               320.5 ns/op            72 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 18.898s

By doing this unsafe approach we are able to save one call to morestack.

Stack usage

SUBQ $0x118, SP       // 280 bytes

Benchmark before
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/normal             18570822                61.33 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-2           20671512                59.85 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-4           20064495                58.73 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-8           19763770                60.18 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal_with_logger                  7673887               157.4 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-2                8318539               143.0 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-4                8584477               139.0 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_with_logger-8                8203886               147.7 ns/op           112 B/op          3 allocs/op
BenchmarkAny/normal_new_goroutine                 273378              3873 ns/op             137 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-2               496189              2141 ns/op              72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-4              1000000              1088 ns/op              72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-8              1743856               678.5 ns/op            72 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 15.922s

Benchmark after
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/normal             15874744                75.15 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-2           16086948                71.64 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-4           16595194                71.02 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal-8           16130025                72.98 ns/op           24 B/op          1 allocs/op
BenchmarkAny/normal_with_logger                  9092430               130.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-2               10157986               122.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-4                9523335               123.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_with_logger-8                9183698               128.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine                1250547               883.7 ns/op            73 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-2              2108619               659.3 ns/op            72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-4              2919674               407.9 ns/op            72 B/op          2 allocs/op
BenchmarkAny/normal_new_goroutine-8              4778667               320.5 ns/op            72 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 18.898s
rabbbit added a commit that referenced this pull request Jul 28, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
rabbbit added a commit that referenced this pull request Jul 28, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
rabbbit added a commit that referenced this pull request Jul 28, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
rabbbit added a commit that referenced this pull request Jul 29, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
rabbbit added a commit that referenced this pull request Jul 30, 2023
…ion)

This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.
- #1305 - my own PR that inline bunch of loops
- https://github.com/uber-go/zap/compare/pawel/any-int5 that does the
  same as above, but is slightly easier to parse
- #1307 - a reflect.TypeOf lookup version

THIS PR IS INCOMPLETE - it shows a possible approach, but I wanted to
get reviewers thoughts before typing everything in.

I originally thought we can use a `type props strucy` intermediary
struct to store the data, but that hits the same problem: every `props`
would get it's own slot on the stack. This avoids this by returning
the raw data.

Pros:
- the implementation is shared between `Any` and strongly typed Fields
- no reflect or unsafe
- reduced the stack significantly - we should be able to get to the same
  ~180 bytes as ~1305.
- no peft penalty for strongly typed versions, at least on ARM64 it's
  compiled away.

Cons:
- the code gets a bit harder to maintain. It's significantly better than
  #1305 I would say though.
rabbbit added a commit that referenced this pull request Jul 30, 2023
…ion)

This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.
- #1305 - my own PR that inline bunch of loops
- https://github.com/uber-go/zap/compare/pawel/any-int5 that does the
  same as above, but is slightly easier to parse
- #1307 - a reflect.TypeOf lookup version

THIS PR IS INCOMPLETE - it shows a possible approach, but I wanted to
get reviewers thoughts before typing everything in.

I originally thought we can use a `type props strucy` intermediary
struct to store the data, but that hits the same problem: every `props`
would get it's own slot on the stack. This avoids this by returning
the raw data.

Pros:
- the implementation is shared between `Any` and strongly typed Fields
- no reflect or unsafe
- reduced the stack significantly - we should be able to get to the same
  ~180 bytes as ~1305.
- no peft penalty for strongly typed versions, at least on ARM64 it's
  compiled away.

Cons:
- the code gets a bit harder to maintain. It's significantly better than
  #1305 I would say though.
abhinav added a commit to abhinav/zap that referenced this pull request Jul 30, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from uber-go#1301, uber-go#1303, uber-go#1304, uber-go#1305, uber-go#1307, and 1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in uber-go#1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

Stack size:
The stack size of zap.Any following this change is 0xc0.

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than uber-go#1305,
which is the smallest stack size of all other attempts.

Allocations:
Everything appears to get inlined with no heap escapes:

    go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

Maintainability:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

Performance:
This is a net improvement on all BenchmarkAny calls
except "any-no-logger" which calls `zap.Any` and discards the result.

```
name                        old time/op    new time/op    delta
Any/str-no-logger-2           8.77ns ± 0%    8.75ns ± 1%     ~     (p=0.159 n=4+5)
Any/any-no-logger-2           54.1ns ± 0%    81.6ns ± 0%  +50.71%  (p=0.016 n=5+4)
Any/str-with-logger-2         1.38µs ± 3%    1.38µs ± 4%     ~     (p=0.841 n=5+5)
Any/any-with-logger-2         1.60µs ±22%    1.37µs ± 1%     ~     (p=0.151 n=5+5)
Any/str-in-go-2               3.41µs ± 1%    3.42µs ± 5%     ~     (p=0.905 n=4+5)
Any/any-in-go-2               5.98µs ± 1%    3.68µs ± 6%  -38.44%  (p=0.008 n=5+5)
Any/str-in-go-with-stack-2    3.42µs ± 2%    3.46µs ± 3%     ~     (p=0.421 n=5+5)
Any/any-in-go-with-stack-2    5.98µs ± 3%    3.65µs ± 3%  -38.95%  (p=0.008 n=5+5)

name                        old alloc/op   new alloc/op   delta
Any/str-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/any-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/str-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/any-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/str-in-go-2                88.5B ± 1%     88.0B ± 0%     ~     (p=0.429 n=4+4)
Any/any-in-go-2                88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)

name                        old allocs/op  new allocs/op  delta
Any/str-no-logger-2             0.00           0.00          ~     (all equal)
Any/any-no-logger-2             0.00           0.00          ~     (all equal)
Any/str-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/any-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/str-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
```

I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
rabbbit added a commit that referenced this pull request Jul 30, 2023
This is a prefactor for #1301, #1302, #1304, #1305, #1307, #1308 and #1310.

We're writing various approaches to reduce the stock size and it's
painful to keep copy-pasting the tests between PRs. This was suggested
in @prashantv in #1307.

The tests are mostly based on tests in #1303, but made "more generic",
as #1307 we might want to test across more than just a single type.
It does make the tests a bit harder to setup. Some of the setup is
inconvenient (we duplicate the value in both `typed` and `any` version
of the tests) but hopefully okay to understand. A fully non-duplicated
alternative would likely require something like #1310 itself.

For #1307 in particular a test against interface type would likely be
needed, so adding it here too.

The tests compare two code paths, with the same arguments, one using a
strongly typed method and second using `zap.Any`. We have:
- a simple "create field" case for a baseline
- a "create and log" case for a realistic case (we typically log the fields)
- a "create and log in a goroutine" case for the pathological case
  we're trying to solve for.
- a "create and long in goroutine in a pre-warmed system" that does the
  above, but before tries to affect the starting goroutine stack size
  to provide an realistic example.
  Without this, for any tests with 2+ goroutines, the cost of `zap.Any`
  is not visible, as we always end up expanding the stack even in the
  strongly typed methods.

The test results are:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/string-typ-no-logger               166879518                6.988 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-typ-no-logger-12            167398297                6.973 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger               87669631                13.97 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger-12            86760837                14.11 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-typ-logger                   3059485               395.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-12                3141176               379.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger                   2995699               401.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger-12                3071046               391.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-go                 784323              1351 ns/op             146 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-12             2000835               613.9 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go                 477486              2479 ns/op             117 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-12             1830955               680.0 ns/op           112 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack           841566              1328 ns/op              96 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack-12       2625226               479.6 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack           486084              2493 ns/op             112 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack-12       2658640               667.9 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-no-logger             147314238                8.034 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-no-logger-12          157857937                7.436 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger             58872349                20.19 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger-12          60532305                20.27 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-logger                 3094204               411.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-12              3163489               383.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger                 2981940               427.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger-12              2777792               394.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-go               911761              1335 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-12           2006440               605.2 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go               467934              2518 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-12           1786076               683.1 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack         855794              1316 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack-12     2598783               434.5 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack         473282              2474 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack-12     2020183               651.9 ns/op           112 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 53.516s
```
@rabbbit rabbbit mentioned this pull request Jul 30, 2023
prashantv pushed a commit that referenced this pull request Jul 31, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
@cdvr1993 cdvr1993 closed this Jul 31, 2023
rabbbit added a commit that referenced this pull request Aug 1, 2023
This is a prefactor for #1301, #1302, #1304, #1305, #1307, #1308 and
#1310.

We're writing various approaches to reduce the stock size and it's
painful to keep copy-pasting the tests between PRs. This was suggested
in @prashantv in #1307.

The tests are mostly based on tests in #1303, but made "more generic",
as #1307 we might want to test across more than just a single type. It
does make the tests a bit harder to setup. Some of the setup is
inconvenient (we duplicate the value in both `typed` and `any` version
of the tests) but hopefully okay to understand. A fully non-duplicated
alternative would likely require something like #1310 itself.

For #1307 in particular a test against interface type would likely be
needed, so adding it here too.

The tests compare two code paths, with the same arguments, one using a
strongly typed method and second using `zap.Any`. We have:
- a simple "create field" case for a baseline
- a "create and log" case for a realistic case (we typically log the
fields)
- a "create and log in a goroutine" case for the pathological case we're
trying to solve for.
- -a "create and long in goroutine in a pre-warmed system" that does the
above- we decided it's not worth the complication.

The test results are:
```
❯  go test -bench BenchmarkAny -benchmem -cpu 1
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/string/field-only/typed    161981473                7.374 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string/field-only/any      82343354                14.67 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string/log/typed            2965648               416.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log/any              2920292               418.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log-go/typed         1000000              1158 ns/op             112 B/op          3 allocs/op
BenchmarkAny/string/log-go/any            553144              2152 ns/op             128 B/op          3 allocs/op
BenchmarkAny/stringer/field-only/typed  160509367                7.548 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer/field-only/any    51330402                23.45 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer/log/typed          3221404               377.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log/any            2726443               393.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log-go/typed       1000000              1129 ns/op             112 B/op          3 allocs/op
BenchmarkAny/stringer/log-go/any          558602              2147 ns/op             128 B/op          3 allocs/op
PASS
ok      go.uber.org/zap 19.426s
```

On gotip:
```
❯  gotip test -bench BenchmarkAny -benchmem -cpu 1

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/string/field-only/typed    155084869                7.603 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string/field-only/any      82740788                14.55 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string/log/typed            2800495               411.6 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log/any              2896258               411.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log-go/typed         1000000              1155 ns/op             112 B/op          3 allocs/op
BenchmarkAny/string/log-go/any            551599              2168 ns/op             128 B/op          3 allocs/op
BenchmarkAny/stringer/field-only/typed  159505488                7.578 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer/field-only/any    51406354                23.78 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer/log/typed          3011210               388.6 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log/any            3010370               395.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log-go/typed       1000000              1161 ns/op             112 B/op          3 allocs/op
BenchmarkAny/stringer/log-go/any          553860              2161 ns/op             128 B/op          3 allocs/op
PASS
ok      go.uber.org/zap 19.391s
```

on amd64 (similar, 2x worse stack growth impact)
```
 % go test -bench BenchmarkAny -benchmem -cpu 1
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/string/field-only/typed    47534053                25.23 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string/field-only/any      36913526                32.57 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string/log/typed            1693508               725.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log/any              1576172               765.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string/log-go/typed          516832              2343 ns/op             112 B/op          3 allocs/op
BenchmarkAny/string/log-go/any            243692              4404 ns/op             128 B/op          3 allocs/op
BenchmarkAny/stringer/field-only/typed  48735537                24.73 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer/field-only/any    26115684                47.24 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer/log/typed          1761630               677.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log/any            1646913               705.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer/log-go/typed        534187              2275 ns/op             112 B/op          3 allocs/op
BenchmarkAny/stringer/log-go/any          273787              4348 ns/op             128 B/op          3 allocs/op
PASS
ok      go.uber.org/zap 18.890s
```
rabbbit added a commit that referenced this pull request Aug 1, 2023
This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.

This PR reduces the stack size from:
```
 field.go:420          0xd16c3                 4881ecf8120000          SUBQ $0x12f8, SP   // 4856
```
to
```
  field.go:420          0xcb603                 4881ecb8000000          SUBQ $0xb8, SP // 184
```
so by ~96%. More crucially, `zap.Any` is now as fast as correctly typed
methods, like `zap.String`, etc.

The downside is the (slight) incrase in the code maitenance - we unroll
as much as we can and rely on the compiler correctly re-using small
variable sizes. While this is not pretty, it feels safe - the changes
were purely mechanical. Future changes and extensions should be easy to
review.

Additionally, the new code is (slightly) faster in all cases since we
remove 1-2 function calls from all paths. The "in new goroutine" path is
most affected, as shown in benchmarks below.

This was largely inspired by conversations with @cdvr1993. We started
looking at this in parallel, but I would have given up if it wasn't for
our conversations.
This particular version was inspired by an earlier version of #1304 -
where I realized that @cdvr1993 is doing a similar dispatching mechanism
that zap is already doing via `zapcore` - a possible optimization.

Longer version:

We have identified an issue where zap.Any can cause performance
degradation due to stack size.

This is apparently cased by the compiler assigning 4.8kb (a zap.Field
per arm of the switch statement) for zap.Any on stack. This can result
in an unnecessary runtime.newstack+runtime.copystack.
A github issue against Go language is pending.

This can be particularly bad if `zap.Any` was to be used in a new
goroutine, since the default goroutine sizes can be as low as 2kb (it can
vary depending on average stack size - see golang/go#18138).

*Most crucially, `zap.Any` is now as fast as a direct dispatch like
`zap.String`.*

10 runs.
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
                           │ before-final.txt │           after-final.txt            │
                           │      sec/op      │    sec/op     vs base                │
Any/str-no-logger                3.106n ±  2%   3.160n ±  1%   +1.75% (p=0.025 n=10)
Any/str-no-logger-2              3.171n ±  4%   3.142n ±  1%        ~ (p=0.593 n=10)
Any/str-no-logger-4              3.108n ±  3%   3.139n ±  2%   +0.97% (p=0.004 n=10)
Any/str-no-logger-8              3.099n ±  2%   3.143n ±  2%        ~ (p=0.086 n=10)
Any/any-no-logger                13.89n ±  2%   12.98n ±  2%   -6.59% (p=0.000 n=10)
Any/any-no-logger-2              13.97n ±  2%   12.96n ±  2%   -7.27% (p=0.000 n=10)
Any/any-no-logger-4              13.83n ±  2%   12.89n ±  2%   -6.83% (p=0.000 n=10)
Any/any-no-logger-8              13.77n ±  2%   12.88n ±  2%   -6.43% (p=0.000 n=10)
Any/str-with-logger              384.1n ±  2%   383.9n ±  6%        ~ (p=0.810 n=10)
Any/str-with-logger-2            367.8n ±  2%   368.5n ±  3%        ~ (p=0.971 n=10)
Any/str-with-logger-4            372.4n ±  2%   368.6n ±  4%        ~ (p=0.912 n=10)
Any/str-with-logger-8            369.8n ±  3%   368.3n ±  3%        ~ (p=0.698 n=10)
Any/any-with-logger              383.8n ±  3%   383.3n ±  6%        ~ (p=0.838 n=10)
Any/any-with-logger-2            370.0n ±  3%   367.6n ±  1%        ~ (p=0.239 n=10)
Any/any-with-logger-4            370.0n ±  3%   368.2n ±  4%        ~ (p=0.631 n=10)
Any/any-with-logger-8            367.6n ±  2%   369.7n ±  3%        ~ (p=0.756 n=10)
Any/str-in-go                    1.334µ ±  3%   1.347µ ±  3%        ~ (p=0.271 n=10)
Any/str-in-go-2                  754.5n ±  3%   744.8n ±  5%        ~ (p=0.481 n=10)
Any/str-in-go-4                  420.2n ± 11%   367.7n ± 31%        ~ (p=0.086 n=10)
Any/str-in-go-8                  557.6n ±  4%   547.1n ± 12%        ~ (p=0.579 n=10)
Any/any-in-go                    2.562µ ±  4%   1.447µ ±  3%  -43.53% (p=0.000 n=10)
Any/any-in-go-2                 1361.0n ±  4%   761.4n ±  7%  -44.06% (p=0.000 n=10)
Any/any-in-go-4                  732.1n ±  9%   397.1n ± 11%  -45.76% (p=0.000 n=10)
Any/any-in-go-8                  541.3n ± 13%   564.6n ±  5%   +4.30% (p=0.041 n=10)
Any/str-in-go-with-stack         1.420µ ±  1%   1.428µ ±  3%        ~ (p=0.670 n=10)
Any/str-in-go-with-stack-2       749.5n ±  4%   771.8n ±  4%        ~ (p=0.123 n=10)
Any/str-in-go-with-stack-4       433.2n ± 15%   400.7n ± 14%        ~ (p=0.393 n=10)
Any/str-in-go-with-stack-8       494.0n ±  7%   490.1n ± 10%        ~ (p=0.853 n=10)
Any/any-in-go-with-stack         2.586µ ±  3%   1.471µ ±  4%  -43.14% (p=0.000 n=10)
Any/any-in-go-with-stack-2      1343.0n ±  3%   773.7n ±  4%  -42.39% (p=0.000 n=10)
Any/any-in-go-with-stack-4       697.7n ±  8%   403.4n ±  9%  -42.17% (p=0.000 n=10)
Any/any-in-go-with-stack-8       490.8n ±  9%   492.8n ±  8%        ~ (p=0.796 n=10)
geomean                          206.3n         182.9n        -11.35%
```

On absolute terms:

Before, on arm64:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3154850               387.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3239221               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3273285               363.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3251991               372.4 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             2944020               401.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           2984863               368.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3265248               363.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3301592               365.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    764239              1423 ns/op             140 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1510189               753.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3013986               369.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2128927               540.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    464083              2551 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  818104              1347 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1587925               698.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2452558               466.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         767626              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1534382               771.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2384058               433.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      3146942               450.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         434194              2524 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       851312              1304 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1570944               710.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2546115               604.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.238s
```

After:
```
❯  go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8

goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/str-with-logger             3202051               382.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           3301683               371.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           3186028               364.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           3061030               371.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             3203704               378.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           3281462               372.8 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           3252879               371.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           3246148               373.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    804132              1404 ns/op             133 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                 1686093               758.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 3075596               430.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 2101650               543.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    845822              1424 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                 1531311               736.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 2618665               464.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2130280               536.2 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         818583              1440 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2      1533379               739.4 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      2507131               399.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2348804               453.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         807199              1526 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2      1590476               783.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      3026263               383.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      2615467               493.8 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.077s
```

And amd64, before:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.58 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.52 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.56 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.50 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              39399811                30.35 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            39448304                30.63 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            39647024                30.32 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            39479619                30.46 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1798702               669.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1862551               647.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1848636               642.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1878465               656.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1776140               684.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1868102               668.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1869589               639.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1782540               648.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    458112              2594 ns/op              91 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  820398              1344 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1392148               969.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1790403               644.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    220327              4897 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  494391              2701 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                  823672              1399 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 1591206               746.8 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         384094              2820 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       809073              1530 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1464598               933.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      1943251               578.0 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         233019              4967 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       356689              2848 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4       791342              1385 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1662126               746.0 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 51.671s
```

After:
```
 % go test -bench BenchmarkAny -benchmem -run errs -cpu 1,2,4,8
goos: linux
goarch: amd64
pkg: go.uber.org/zap
cpu: AMD EPYC 7B13
BenchmarkAny/str-no-logger              100000000               11.77 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-2            100000000               11.75 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-4            100000000               11.76 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-no-logger-8            100000000               11.69 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger              49795383                24.33 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-2            48821454                24.31 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-4            49452686                24.79 ns/op            0 B/op          0 allocs/op
BenchmarkAny/any-no-logger-8            49359926                24.26 ns/op            0 B/op          0 allocs/op
BenchmarkAny/str-with-logger             1808188               700.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-2           1894179               643.9 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-4           1858263               649.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-with-logger-8           1879894               645.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger             1817276               663.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-2           1906438               637.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-4           1837354               641.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/any-with-logger-8           1909658               648.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/str-in-go                    468484              2463 ns/op              96 B/op          2 allocs/op
BenchmarkAny/str-in-go-2                  726475              1465 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-4                 1285284               958.9 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-8                 1746547               573.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go                    426568              2715 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-2                  611106              1703 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-4                 1000000              1017 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-8                 2220459               625.7 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack         429721              2673 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-2       637306              1593 ns/op              88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-4      1301713               902.1 ns/op            88 B/op          2 allocs/op
BenchmarkAny/str-in-go-with-stack-8      2012583               651.6 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack         391810              2833 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-2       675589              1639 ns/op              88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-4      1219318               970.3 ns/op            88 B/op          2 allocs/op
BenchmarkAny/any-in-go-with-stack-8      1825632               574.6 ns/op            88 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 50.294s
```
rabbbit added a commit that referenced this pull request Aug 1, 2023
…ion)

This is an alternative to:
- #1301 and #1302 and #1304 - a series of PRs that are faster than this
  one. However, they rely on unsafe.
- #1303 - my own PR that uses closures, to reduce the stack size by 60%.
- #1305 - my own PR that inline bunch of loops
- https://github.com/uber-go/zap/compare/pawel/any-int5 that does the
  same as above, but is slightly easier to parse
- #1307 - a reflect.TypeOf lookup version

THIS PR IS INCOMPLETE - it shows a possible approach, but I wanted to
get reviewers thoughts before typing everything in.

I originally thought we can use a `type props strucy` intermediary
struct to store the data, but that hits the same problem: every `props`
would get it's own slot on the stack. This avoids this by returning
the raw data.

Pros:
- the implementation is shared between `Any` and strongly typed Fields
- no reflect or unsafe
- reduced the stack significantly - we should be able to get to the same
  ~180 bytes as ~1305.
- no peft penalty for strongly typed versions, at least on ARM64 it's
  compiled away.

Cons:
- the code gets a bit harder to maintain. It's significantly better than
  #1305 I would say though.
abhinav added a commit to abhinav/zap that referenced this pull request Aug 1, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from uber-go#1301, uber-go#1303, uber-go#1304, uber-go#1305, uber-go#1307, and 1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in uber-go#1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

Stack size:
The stack size of zap.Any following this change is 0xc0.

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than uber-go#1305,
which is the smallest stack size of all other attempts.

Allocations:
Everything appears to get inlined with no heap escapes:

    go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

Maintainability:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

Performance:
This is a net improvement on all BenchmarkAny calls
except "any-no-logger" which calls `zap.Any` and discards the result.

```
name                        old time/op    new time/op    delta
Any/str-no-logger-2           8.77ns ± 0%    8.75ns ± 1%     ~     (p=0.159 n=4+5)
Any/any-no-logger-2           54.1ns ± 0%    81.6ns ± 0%  +50.71%  (p=0.016 n=5+4)
Any/str-with-logger-2         1.38µs ± 3%    1.38µs ± 4%     ~     (p=0.841 n=5+5)
Any/any-with-logger-2         1.60µs ±22%    1.37µs ± 1%     ~     (p=0.151 n=5+5)
Any/str-in-go-2               3.41µs ± 1%    3.42µs ± 5%     ~     (p=0.905 n=4+5)
Any/any-in-go-2               5.98µs ± 1%    3.68µs ± 6%  -38.44%  (p=0.008 n=5+5)
Any/str-in-go-with-stack-2    3.42µs ± 2%    3.46µs ± 3%     ~     (p=0.421 n=5+5)
Any/any-in-go-with-stack-2    5.98µs ± 3%    3.65µs ± 3%  -38.95%  (p=0.008 n=5+5)

name                        old alloc/op   new alloc/op   delta
Any/str-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/any-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/str-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/any-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/str-in-go-2                88.5B ± 1%     88.0B ± 0%     ~     (p=0.429 n=4+4)
Any/any-in-go-2                88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)

name                        old allocs/op  new allocs/op  delta
Any/str-no-logger-2             0.00           0.00          ~     (all equal)
Any/any-no-logger-2             0.00           0.00          ~     (all equal)
Any/str-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/any-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/str-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
```

I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
abhinav added a commit to abhinav/zap that referenced this pull request Aug 1, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from uber-go#1301, uber-go#1303, uber-go#1304, uber-go#1305, uber-go#1307, and 1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in uber-go#1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

Stack size:
The stack size of zap.Any following this change is 0xc0.

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than uber-go#1305,
which is the smallest stack size of all other attempts.

Allocations:
Everything appears to get inlined with no heap escapes:

    go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

Maintainability:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

Performance:
This is a net improvement on all BenchmarkAny calls
except "any-no-logger" which calls `zap.Any` and discards the result.

```
name                        old time/op    new time/op    delta
Any/str-no-logger-2           8.77ns ± 0%    8.75ns ± 1%     ~     (p=0.159 n=4+5)
Any/any-no-logger-2           54.1ns ± 0%    81.6ns ± 0%  +50.71%  (p=0.016 n=5+4)
Any/str-with-logger-2         1.38µs ± 3%    1.38µs ± 4%     ~     (p=0.841 n=5+5)
Any/any-with-logger-2         1.60µs ±22%    1.37µs ± 1%     ~     (p=0.151 n=5+5)
Any/str-in-go-2               3.41µs ± 1%    3.42µs ± 5%     ~     (p=0.905 n=4+5)
Any/any-in-go-2               5.98µs ± 1%    3.68µs ± 6%  -38.44%  (p=0.008 n=5+5)
Any/str-in-go-with-stack-2    3.42µs ± 2%    3.46µs ± 3%     ~     (p=0.421 n=5+5)
Any/any-in-go-with-stack-2    5.98µs ± 3%    3.65µs ± 3%  -38.95%  (p=0.008 n=5+5)

name                        old alloc/op   new alloc/op   delta
Any/str-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/any-no-logger-2            0.00B          0.00B          ~     (all equal)
Any/str-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/any-with-logger-2          64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/str-in-go-2                88.5B ± 1%     88.0B ± 0%     ~     (p=0.429 n=4+4)
Any/any-in-go-2                88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2     88.0B ± 0%     88.0B ± 0%     ~     (all equal)

name                        old allocs/op  new allocs/op  delta
Any/str-no-logger-2             0.00           0.00          ~     (all equal)
Any/any-no-logger-2             0.00           0.00          ~     (all equal)
Any/str-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/any-with-logger-2           1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/str-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-2                 2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/str-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
Any/any-in-go-with-stack-2      2.00 ± 0%      2.00 ± 0%     ~     (all equal)
```

I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
abhinav added a commit that referenced this pull request Aug 1, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from #1301, #1303, #1304, #1305, #1307, and #1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in #1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

**Stack size**:
The stack size of zap.Any following this change is 0xc0 (192 bytes).

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than #1305,
which is the smallest stack size of all other attempts.

**Allocations**:
Everything appears to get inlined with no heap escapes:

    % go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'
    [no output]

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

**Maintainability**:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

**Performance**:
This is a net improvement against master on BenchmarkAny's
log-go checks that log inside a new goroutine.

```
name                           old time/op    new time/op    delta
Any/string/field-only/typed      25.2ns ± 1%    25.6ns ± 2%     ~     (p=0.460 n=5+5)
Any/string/field-only/any        56.9ns ± 3%    79.4ns ± 0%  +39.55%  (p=0.008 n=5+5)
Any/string/log/typed             1.47µs ± 0%    1.49µs ± 4%   +1.58%  (p=0.016 n=4+5)
Any/string/log/any               1.53µs ± 2%    1.55µs ± 1%   +1.37%  (p=0.016 n=5+5)
Any/string/log-go/typed          5.97µs ± 6%    5.99µs ± 1%     ~     (p=0.151 n=5+5)
Any/string/log-go/any            10.9µs ± 0%     6.2µs ± 0%  -43.32%  (p=0.008 n=5+5)
Any/stringer/field-only/typed    25.3ns ± 1%    25.5ns ± 1%   +1.09%  (p=0.008 n=5+5)
Any/stringer/field-only/any      85.5ns ± 1%   124.5ns ± 0%  +45.66%  (p=0.008 n=5+5)
Any/stringer/log/typed           1.43µs ± 1%    1.42µs ± 2%     ~     (p=0.175 n=4+5)
Any/stringer/log/any             1.50µs ± 1%    1.56µs ± 6%   +4.20%  (p=0.008 n=5+5)
Any/stringer/log-go/typed        5.94µs ± 0%    5.92µs ± 0%   -0.40%  (p=0.032 n=5+5)
Any/stringer/log-go/any          11.1µs ± 2%     6.3µs ± 0%  -42.93%  (p=0.008 n=5+5)

name                           old alloc/op   new alloc/op   delta
Any/string/field-only/typed       0.00B          0.00B          ~     (all equal)
Any/string/field-only/any         0.00B          0.00B          ~     (all equal)
Any/string/log/typed              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log/any                64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log-go/typed            112B ± 0%      112B ± 0%     ~     (all equal)
Any/string/log-go/any              128B ± 0%      128B ± 0%     ~     (all equal)
Any/stringer/field-only/typed     0.00B          0.00B          ~     (all equal)
Any/stringer/field-only/any       0.00B          0.00B          ~     (all equal)
Any/stringer/log/typed            64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log/any              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log-go/typed          112B ± 0%      112B ± 0%     ~     (all equal)
Any/stringer/log-go/any            128B ± 0%      128B ± 0%     ~     (all equal)

name                           old allocs/op  new allocs/op  delta
Any/string/field-only/typed        0.00           0.00          ~     (all equal)
Any/string/field-only/any          0.00           0.00          ~     (all equal)
Any/string/log/typed               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log/any                 1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log-go/typed            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/string/log-go/any              3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/field-only/typed      0.00           0.00          ~     (all equal)
Any/stringer/field-only/any        0.00           0.00          ~     (all equal)
Any/stringer/log/typed             1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log/any               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log-go/typed          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/log-go/any            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
```

It causes a regression in "field-only"
which calls the field constructor and discards the result
without using it in a logger.
I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
rabbbit added a commit that referenced this pull request Aug 2, 2023
This is a prefactor for #1301, #1302, #1304, #1305, #1307, #1308 and #1310.

We're writing various approaches to reduce the stack size and it's
painful to keep copy-pasting the tests between PRs. This was suggested
in @prashantv in #1307.

The tests are mostly based on tests in #1303, but made "more generic",
as #1307 we might want to test across more than just a single type.
It does make the tests a bit harder to setup. Some of the setup is
inconvenient (we duplicate the value in both `typed` and `any` version
of the tests) but hopefully okay to understand. A fully non-duplicated
alternative would likely require something like #1310 itself.

For #1307 in particular a test against interface type would likely be
needed, so adding it here too.

The tests compare two code paths, with the same arguments, one using a
strongly typed method and second using `zap.Any`. We have:
- a simple "create field" case for a baseline
- a "create and log" case for a realistic case (we typically log the fields)
- a "create and log in a goroutine" case for the pathological case
  we're trying to solve for.
- a "create and long in goroutine in a pre-warmed system" that does the
  above, but before tries to affect the starting goroutine stack size
  to provide an realistic example.
  Without this, for any tests with 2+ goroutines, the cost of `zap.Any`
  is not visible, as we always end up expanding the stack even in the
  strongly typed methods.

The test results are:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/string-typ-no-logger               166879518                6.988 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-typ-no-logger-12            167398297                6.973 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger               87669631                13.97 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger-12            86760837                14.11 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-typ-logger                   3059485               395.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-12                3141176               379.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger                   2995699               401.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger-12                3071046               391.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-go                 784323              1351 ns/op             146 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-12             2000835               613.9 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go                 477486              2479 ns/op             117 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-12             1830955               680.0 ns/op           112 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack           841566              1328 ns/op              96 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack-12       2625226               479.6 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack           486084              2493 ns/op             112 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack-12       2658640               667.9 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-no-logger             147314238                8.034 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-no-logger-12          157857937                7.436 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger             58872349                20.19 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger-12          60532305                20.27 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-logger                 3094204               411.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-12              3163489               383.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger                 2981940               427.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger-12              2777792               394.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-go               911761              1335 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-12           2006440               605.2 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go               467934              2518 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-12           1786076               683.1 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack         855794              1316 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack-12     2598783               434.5 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack         473282              2474 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack-12     2020183               651.9 ns/op           112 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 53.516s
```
rabbbit pushed a commit that referenced this pull request Aug 2, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from #1301, #1303, #1304, #1305, #1307, and #1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in #1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

**Stack size**:
The stack size of zap.Any following this change is 0xc0 (192 bytes).

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than #1305,
which is the smallest stack size of all other attempts.

**Allocations**:
Everything appears to get inlined with no heap escapes:

    % go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'
    [no output]

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

**Maintainability**:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

**Performance**:
This is a net improvement against master on BenchmarkAny's
log-go checks that log inside a new goroutine.

```
name                           old time/op    new time/op    delta
Any/string/field-only/typed      25.2ns ± 1%    25.6ns ± 2%     ~     (p=0.460 n=5+5)
Any/string/field-only/any        56.9ns ± 3%    79.4ns ± 0%  +39.55%  (p=0.008 n=5+5)
Any/string/log/typed             1.47µs ± 0%    1.49µs ± 4%   +1.58%  (p=0.016 n=4+5)
Any/string/log/any               1.53µs ± 2%    1.55µs ± 1%   +1.37%  (p=0.016 n=5+5)
Any/string/log-go/typed          5.97µs ± 6%    5.99µs ± 1%     ~     (p=0.151 n=5+5)
Any/string/log-go/any            10.9µs ± 0%     6.2µs ± 0%  -43.32%  (p=0.008 n=5+5)
Any/stringer/field-only/typed    25.3ns ± 1%    25.5ns ± 1%   +1.09%  (p=0.008 n=5+5)
Any/stringer/field-only/any      85.5ns ± 1%   124.5ns ± 0%  +45.66%  (p=0.008 n=5+5)
Any/stringer/log/typed           1.43µs ± 1%    1.42µs ± 2%     ~     (p=0.175 n=4+5)
Any/stringer/log/any             1.50µs ± 1%    1.56µs ± 6%   +4.20%  (p=0.008 n=5+5)
Any/stringer/log-go/typed        5.94µs ± 0%    5.92µs ± 0%   -0.40%  (p=0.032 n=5+5)
Any/stringer/log-go/any          11.1µs ± 2%     6.3µs ± 0%  -42.93%  (p=0.008 n=5+5)

name                           old alloc/op   new alloc/op   delta
Any/string/field-only/typed       0.00B          0.00B          ~     (all equal)
Any/string/field-only/any         0.00B          0.00B          ~     (all equal)
Any/string/log/typed              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log/any                64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log-go/typed            112B ± 0%      112B ± 0%     ~     (all equal)
Any/string/log-go/any              128B ± 0%      128B ± 0%     ~     (all equal)
Any/stringer/field-only/typed     0.00B          0.00B          ~     (all equal)
Any/stringer/field-only/any       0.00B          0.00B          ~     (all equal)
Any/stringer/log/typed            64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log/any              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log-go/typed          112B ± 0%      112B ± 0%     ~     (all equal)
Any/stringer/log-go/any            128B ± 0%      128B ± 0%     ~     (all equal)

name                           old allocs/op  new allocs/op  delta
Any/string/field-only/typed        0.00           0.00          ~     (all equal)
Any/string/field-only/any          0.00           0.00          ~     (all equal)
Any/string/log/typed               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log/any                 1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log-go/typed            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/string/log-go/any              3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/field-only/typed      0.00           0.00          ~     (all equal)
Any/stringer/field-only/any        0.00           0.00          ~     (all equal)
Any/stringer/log/typed             1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log/any               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log-go/typed          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/log-go/any            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
```

It causes a regression in "field-only"
which calls the field constructor and discards the result
without using it in a logger.
I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
sywhang pushed a commit that referenced this pull request Aug 2, 2023
This is a prefactor for #1301, #1302, #1304, #1305, #1307, #1308 and #1310.

We're writing various approaches to reduce the stock size and it's
painful to keep copy-pasting the tests between PRs. This was suggested
in @prashantv in #1307.

The tests are mostly based on tests in #1303, but made "more generic",
as #1307 we might want to test across more than just a single type.
It does make the tests a bit harder to setup. Some of the setup is
inconvenient (we duplicate the value in both `typed` and `any` version
of the tests) but hopefully okay to understand. A fully non-duplicated
alternative would likely require something like #1310 itself.

For #1307 in particular a test against interface type would likely be
needed, so adding it here too.

The tests compare two code paths, with the same arguments, one using a
strongly typed method and second using `zap.Any`. We have:
- a simple "create field" case for a baseline
- a "create and log" case for a realistic case (we typically log the fields)
- a "create and log in a goroutine" case for the pathological case
  we're trying to solve for.
- a "create and long in goroutine in a pre-warmed system" that does the
  above, but before tries to affect the starting goroutine stack size
  to provide an realistic example.
  Without this, for any tests with 2+ goroutines, the cost of `zap.Any`
  is not visible, as we always end up expanding the stack even in the
  strongly typed methods.

The test results are:
```
goos: darwin
goarch: arm64
pkg: go.uber.org/zap
BenchmarkAny/string-typ-no-logger               166879518                6.988 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-typ-no-logger-12            167398297                6.973 ns/op           0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger               87669631                13.97 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-any-no-logger-12            86760837                14.11 ns/op            0 B/op          0 allocs/op
BenchmarkAny/string-typ-logger                   3059485               395.5 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-12                3141176               379.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger                   2995699               401.3 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-any-logger-12                3071046               391.1 ns/op            64 B/op          1 allocs/op
BenchmarkAny/string-typ-logger-go                 784323              1351 ns/op             146 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-12             2000835               613.9 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go                 477486              2479 ns/op             117 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-12             1830955               680.0 ns/op           112 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack           841566              1328 ns/op              96 B/op          2 allocs/op
BenchmarkAny/string-typ-logger-go-stack-12       2625226               479.6 ns/op            96 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack           486084              2493 ns/op             112 B/op          2 allocs/op
BenchmarkAny/string-any-logger-go-stack-12       2658640               667.9 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-no-logger             147314238                8.034 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-no-logger-12          157857937                7.436 ns/op           0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger             58872349                20.19 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-any-no-logger-12          60532305                20.27 ns/op            0 B/op          0 allocs/op
BenchmarkAny/stringer-typ-logger                 3094204               411.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-12              3163489               383.7 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger                 2981940               427.2 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-any-logger-12              2777792               394.0 ns/op            64 B/op          1 allocs/op
BenchmarkAny/stringer-typ-logger-go               911761              1335 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-12           2006440               605.2 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go               467934              2518 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-12           1786076               683.1 ns/op           112 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack         855794              1316 ns/op              96 B/op          2 allocs/op
BenchmarkAny/stringer-typ-logger-go-stack-12     2598783               434.5 ns/op            96 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack         473282              2474 ns/op             112 B/op          2 allocs/op
BenchmarkAny/stringer-any-logger-go-stack-12     2020183               651.9 ns/op           112 B/op          2 allocs/op
PASS
ok      go.uber.org/zap 53.516s
```

reviews

rename

review

farewell, my friend

dummy
sywhang pushed a commit that referenced this pull request Aug 2, 2023
Yet another attempt at reducing the stack size of zap.Any,
borrowing from #1301, #1303, #1304, #1305, #1307, and #1308.

This approach defines a generic data type for field constructors
of a specific type. This is similar to the lookup map in #1307,
minus the map lookup, the interface match, or reflection.

    type anyFieldC[T any] func(string, T) Field

The generic data type provides a non-generic method
matching the interface:

    interface{ Any(string, any) Field }

**Stack size**:
The stack size of zap.Any following this change is 0xc0 (192 bytes).

    % go build -gcflags -S 2>&1 | grep ^go.uber.org/zap.Any
    go.uber.org/zap.Any STEXT size=5861 args=0x20 locals=0xc0 funcid=0x0 align=0x0

This is just 8 bytes more than #1305,
which is the smallest stack size of all other attempts.

**Allocations**:
Everything appears to get inlined with no heap escapes:

    % go build -gcflags -m 2>&1 |
      grep field.go |
      perl -n -e 'next unless m{^./field.go:(\d+)}; print if ($1 >= 413)' |
      grep 'escapes'
    [no output]

(Line 413 declares anyFieldC)

Besides that, the output of `-m` for the relevant section of code
consists of almost entirely:

    ./field.go:415:6: can inline anyFieldC[go.shape.bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: can inline anyFieldC[go.shape.complex128].Any
    [...]
    ./field.go:415:6: inlining call to anyFieldC[go.shape.complex128].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.[]bool].Any
    ./field.go:415:6: inlining call to anyFieldC[go.shape.bool].Any

Followed by:

    ./field.go:428:10: leaking param: key
    ./field.go:428:22: leaking param: value

**Maintainability**:
Unlike some of the other approaches, this variant is more maintainable.
The `zap.Any` function looks roughly the same.
Adding new branches there is obvious, and requires no duplication.

**Performance**:
This is a net improvement against master on BenchmarkAny's
log-go checks that log inside a new goroutine.

```
name                           old time/op    new time/op    delta
Any/string/field-only/typed      25.2ns ± 1%    25.6ns ± 2%     ~     (p=0.460 n=5+5)
Any/string/field-only/any        56.9ns ± 3%    79.4ns ± 0%  +39.55%  (p=0.008 n=5+5)
Any/string/log/typed             1.47µs ± 0%    1.49µs ± 4%   +1.58%  (p=0.016 n=4+5)
Any/string/log/any               1.53µs ± 2%    1.55µs ± 1%   +1.37%  (p=0.016 n=5+5)
Any/string/log-go/typed          5.97µs ± 6%    5.99µs ± 1%     ~     (p=0.151 n=5+5)
Any/string/log-go/any            10.9µs ± 0%     6.2µs ± 0%  -43.32%  (p=0.008 n=5+5)
Any/stringer/field-only/typed    25.3ns ± 1%    25.5ns ± 1%   +1.09%  (p=0.008 n=5+5)
Any/stringer/field-only/any      85.5ns ± 1%   124.5ns ± 0%  +45.66%  (p=0.008 n=5+5)
Any/stringer/log/typed           1.43µs ± 1%    1.42µs ± 2%     ~     (p=0.175 n=4+5)
Any/stringer/log/any             1.50µs ± 1%    1.56µs ± 6%   +4.20%  (p=0.008 n=5+5)
Any/stringer/log-go/typed        5.94µs ± 0%    5.92µs ± 0%   -0.40%  (p=0.032 n=5+5)
Any/stringer/log-go/any          11.1µs ± 2%     6.3µs ± 0%  -42.93%  (p=0.008 n=5+5)

name                           old alloc/op   new alloc/op   delta
Any/string/field-only/typed       0.00B          0.00B          ~     (all equal)
Any/string/field-only/any         0.00B          0.00B          ~     (all equal)
Any/string/log/typed              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log/any                64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/string/log-go/typed            112B ± 0%      112B ± 0%     ~     (all equal)
Any/string/log-go/any              128B ± 0%      128B ± 0%     ~     (all equal)
Any/stringer/field-only/typed     0.00B          0.00B          ~     (all equal)
Any/stringer/field-only/any       0.00B          0.00B          ~     (all equal)
Any/stringer/log/typed            64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log/any              64.0B ± 0%     64.0B ± 0%     ~     (all equal)
Any/stringer/log-go/typed          112B ± 0%      112B ± 0%     ~     (all equal)
Any/stringer/log-go/any            128B ± 0%      128B ± 0%     ~     (all equal)

name                           old allocs/op  new allocs/op  delta
Any/string/field-only/typed        0.00           0.00          ~     (all equal)
Any/string/field-only/any          0.00           0.00          ~     (all equal)
Any/string/log/typed               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log/any                 1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/string/log-go/typed            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/string/log-go/any              3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/field-only/typed      0.00           0.00          ~     (all equal)
Any/stringer/field-only/any        0.00           0.00          ~     (all equal)
Any/stringer/log/typed             1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log/any               1.00 ± 0%      1.00 ± 0%     ~     (all equal)
Any/stringer/log-go/typed          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
Any/stringer/log-go/any            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
```

It causes a regression in "field-only"
which calls the field constructor and discards the result
without using it in a logger.
I believe this is acceptable because that's not a real use case;
we expect the result to be used with a logger.
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