assume the runtime range of align_offset

[scottmcm]

Found when I saw code with align_to having extraneous checks.

Demo that LLVM can't do this today: https://rust.godbolt.org/z/6dnG749bq

(It's filed as llvm/llvm-project#62502.)

[rustbot]

r? @Mark-Simulacrum

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[thomcc]

I've wanted this for a while. I still have a lot of criticisms with the align_to API, but this should make it usable a lot more of the time.

@bors r+ rollup=never

[bors]

📌 Commit 3afe8cdfa8731abbcdde929ccee46ec367a4bc75 has been approved by thomcc

It is now in the queue for this repository.

[thomcc]

Ah, compile errors. r=me with those fixed.

@bors r-

(P.S. Sorry if there are some sporatic comments from me here, I'm on a plane and the internet is... very spotty)

[scottmcm]

Ah, the assume being conditional blocked the branchless-ness that the assembly test was checking. Luckily that didn't need to be conditional -- it's mathematically true -- so I just moved a bit of code earlier and the assembly test passes without needing any changes.

I also expanded the codegen test a bunch.

[scottmcm]

r? thomcc
@bors r=thomcc

[bors]

📌 Commit 2160e5d75ddfa39c64f1a4326664a2a848debf11 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit 2160e5d75ddfa39c64f1a4326664a2a848debf11 with merge d27debbe02b250d988f49fe6dced11e6147126f4...

[bors]

💔 Test failed - checks-actions

[scottmcm]

Oh, when I added more to the tests it included something that adds extra checking in debug, and thus made the optimizations not work and the test fail. Fixed.

@bors r=thomcc

[bors]

📌 Commit 9c57cdbd8e0d4b72016f5799acef89f1978e1b85 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit 9c57cdbd8e0d4b72016f5799acef89f1978e1b85 with merge 5e8369d4e4c917e5d226b720b9b2ad5054f2398f...

[bors]

💔 Test failed - checks-actions

[scottmcm]

Ah, of course, I got the 32-vs-64-bit differences right in 19 places, but there are 20 🤬

@bors r=thomcc

[bors]

📌 Commit a1e5c65 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit a1e5c65 with merge 4a18324...

[bors]

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing 4a18324 to master...

[rust-timer]

Finished benchmarking commit (4a18324): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.0%	[-3.6%, -2.5%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	-1.5%	[-1.5%, -1.5%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 654.413s -> 653.437s (-0.15%)

[rust-log-analyzer]

The job x86_64-gnu-llvm-14 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

normalized stderr:
warning: the feature `const_ptr_read` has been stable since 1.71.0-nightly and no longer requires an attribute to enable
  --> $DIR/issue-105821.rs:4:30
   |
LL | #![feature(adt_const_params, const_ptr_read, generic_const_exprs)]
   |
   = note: `#[warn(stable_features)]` on by default

warning: 1 warning emitted
---
To only update this specific test, also pass `--test-args const-generics/issues/issue-105821.rs`

error: 1 errors occurred comparing output.
status: exit status: 0
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/const-generics/issues/issue-105821.rs" "-Zthreads=1" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Zdeduplicate-diagnostics=no" "-Cstrip=debuginfo" "--remap-path-prefix=/checkout/tests/ui=fake-test-src-base" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/issues/issue-105821" "-A" "unused" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/issues/issue-105821/auxiliary"
stdout: none
warning: the feature `const_ptr_read` has been stable since 1.71.0-nightly and no longer requires an attribute to enable
  --> fake-test-src-base/const-generics/issues/issue-105821.rs:4:30
   |
   |
LL | #![feature(adt_const_params, const_ptr_read, generic_const_exprs)]
   |
   = note: `#[warn(stable_features)]` on by default

warning: 1 warning emitted