interpret: get_ptr_alloc_mut: lookup allocation only once

[RalfJung]

I don't think this will make a big perf difference, but it makes this function symmetric with get_ptr_alloc -- and it's always nice to successfully solve a borrow checker puzzle like this. ;)

[rustbot]

r? @estebank

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[rustbot]

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

[RalfJung]

This is probably pointless, I don't think our ctfe-stress test even does many writes...
@rust-timer queue
@bors try

[bors]

⌛ Trying commit 4e8ddbd with merge cc84819...

[bors]

☀️ Try build successful - checks-actions
Build commit: cc84819 (cc848194add2182f402a65d443478051663979ba)

[rust-timer]

Finished benchmarking commit (cc84819): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.8%, -0.6%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

Cycles

Results (primary 4.8%)

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)	4.8%	[4.8%, 4.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	4.8%	[4.8%, 4.8%]	1

Binary size

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

Bootstrap: 757.632s -> 757.094s (-0.07%)
Artifact size: 341.17 MiB -> 341.09 MiB (-0.02%)

[saethlin]

To save anyone else a few clicks, the benchmark that improves above has a huge static initializer. It does a lot of writes.

r=me when you fix the conflicts :)

[RalfJung]

@bors r=saethlin

[bors]

📌 Commit f16f09d has been approved by saethlin

It is now in the queue for this repository.

[bors]

⌛ Testing commit f16f09d with merge 1ae2688...

[bors]

☀️ Test successful - checks-actions
Approved by: saethlin
Pushing 1ae2688 to master...

[rust-timer]

Finished benchmarking commit (1ae2688): 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 (primary 3.2%, secondary -2.7%)

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)	3.2%	[3.2%, 3.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	3.2%	[3.2%, 3.2%]	1

Cycles

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

Binary size

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

Bootstrap: 760.068s -> 759.207s (-0.11%)
Artifact size: 340.57 MiB -> 341.12 MiB (0.16%)