Stop emitting non-power-of-two vectors in (non-portable-SIMD) codegen by scottmcm · Pull Request #115236 · rust-lang/rust

scottmcm · 2023-08-26T03:14:02Z

It's unclear what makes this not work sometimes, since it often does work, so for now just disable the unusual cases. A future PR can consider doing something smarter, but this is an easy and safe tweak that we can do to resolve the regressions for now.

rustbot · 2023-08-26T03:14:07Z

r? @WaffleLapkin

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workingjubilee · 2023-08-26T03:26:51Z

+#[no_mangle]
+// CHECK-LABEL: @replace_short_array_4(
+pub fn replace_short_array_4(r: &mut [u32; 4], v: [u32; 4]) -> [u32; 4] {
+ // CHECK-NOT: alloca
+ // CHECK: %[[R:.+]] = load <4 x i32>, ptr %r, align 4
+ // CHECK: store <4 x i32> %[[R]], ptr %result
+ // CHECK: %[[V:.+]] = load <4 x i32>, ptr %v, align 4
+ // CHECK: store <4 x i32> %[[V]], ptr %r


compiler-errors

r=me unless you want a specific review

scottmcm · 2023-08-26T06:02:05Z

@bors r=compiler-errors rollup=never

bors · 2023-08-26T06:02:07Z

📌 Commit 84e305d has been approved by compiler-errors

It is now in the queue for this repository.

bors · 2023-08-26T06:02:16Z

⌛ Testing commit 84e305d with merge 766c0c0...

Noratrieb · 2023-08-26T07:05:37Z

note that this is also what killed the MIPS backend so it seems reasonable to believe that LLVM backends are not good at this in general

bors · 2023-08-26T07:47:19Z

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 766c0c0 to master...

bors · 2023-08-26T07:47:19Z

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 766c0c0 to master...

rust-timer · 2023-08-26T17:04:38Z

Finished benchmarking commit (766c0c0): 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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-2.8%, -2.8%]	1
All ❌✅ (primary)	-	-	0

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: 631.911s -> 631.395s (-0.08%)
Artifact size: 315.57 MiB -> 315.55 MiB (-0.01%)

scottmcm · 2023-08-26T20:24:09Z

Beta nomination

This is to address the perf hit seen in #115212

It should be very safe, since it's only one line of product code, and all it does is disable #111999 in more cases, leaving those cases to use the same codepath as in 1.71.

(It would also be possible to disable 111999 entirely, but I've also seen cases like https://rust.godbolt.org/z/7s9ob85ja where the vector codegen helps avoid byte-by-byte movs, so this targets the known-bad case. As Nils mentions in #115236 (comment), non-power-of-two vectors also seem to be less well exercised in backends, so this avoids those problems by only using power-of-two vectors.)

EDIT: The original issue reporter confirmed in #115212 (comment) that this fixes it.

apiraino · 2023-09-01T09:42:23Z

Beta backport accepted as per compiler team on Zulip

Also in favor of a stable backport in case a 1.72.1 materializes (zulip comment).

@rustbot label +beta-accepted +stable-accepted

[beta] backports - Contents of reachable statics is reachable rust-lang#115114 - Revert "Suggest using `Arc` on `!Send`/`!Sync` types" rust-lang#115311 - Stop emitting non-power-of-two vectors in (non-portable-SIMD) codegen rust-lang#115236 - Do not forget to pass DWARF fragment information to LLVM. rust-lang#115139 - rustdoc: use unicode-aware checks for redundant explicit link fastpath rust-lang#115070 r? cuviper

…Simulacrum [stable] 1.72.1 release This backports: * Remove assert that checks type equality rust-lang#115215 * implied bounds: do not ICE on unconstrained region vars rust-lang#115559 * rustdoc: correctly deal with self ty params when eliding default object lifetimes rust-lang#115276 * Stop emitting non-power-of-two vectors in (non-portable-SIMD) codegen rust-lang#115236 * Normalize before checking if local is freeze in deduced_param_attrs rust-lang#114948 Some cherry-picks required merge conflict resolution, we'll see if I got it right based on CI (rustdoc fix and LLVM codegen test). r? `@Mark-Simulacrum`

> 1.72.1 resolves a few regressions introduced in 1.72.0: > - [Partially revert codegen change, improving codegen](rust-lang/rust#115236) > - [rustdoc: Fix self ty params in objects with lifetimes](rust-lang/rust#115276) > - [Fix regression in compile times](rust-lang/rust#114948) > - Resolve some ICEs in the compiler: > - [#115215](rust-lang/rust#115215) > - [#115559](rust-lang/rust#115559)

Stop emitting non-power-of-two vectors in basic LLVM codegen
84e305d

scottmcm added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Aug 26, 2023

rustbot assigned WaffleLapkin Aug 26, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 26, 2023

scottmcm mentioned this pull request Aug 26, 2023
Nearly 50% performance regression when copying/moving small byte arrays between 1.71 and 1.72 #115212
Closed

workingjubilee reviewed Aug 26, 2023
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compiler-errors approved these changes Aug 26, 2023
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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 26, 2023

bors added merged-by-bors This PR was explicitly merged by bors. labels Aug 26, 2023

bors merged commit 766c0c0 into rust-lang:masterAug 26, 2023

rustbot added this to the 1.74.0 milestone Aug 26, 2023

bors mentioned this pull request Aug 26, 2023
Avoid memcpy in codegen for more types, notably Vec#112733
Closed

scottmcm deleted the less-vector branch August 26, 2023 08:32

wesleywiser added the stable-nominated Nominated for backporting to the compiler in the stable channel. label Aug 31, 2023

rustbot added beta-accepted Accepted for backporting to the compiler in the beta channel. stable-accepted Accepted for backporting to the compiler in the stable channel. labels Sep 1, 2023

cuviper mentioned this pull request Sep 1, 2023
[beta] backports #115442
Merged

cuviper modified the milestones: 1.74.0, 1.73.0 Sep 1, 2023

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Sep 1, 2023

Mark-Simulacrum modified the milestones: 1.73.0, 1.72.1 Sep 12, 2023

Mark-Simulacrum removed the stable-nominated Nominated for backporting to the compiler in the stable channel. label Sep 12, 2023

Mark-Simulacrum mentioned this pull request Sep 12, 2023
[stable] 1.72.1 release #115787
Merged

mmastrac mentioned this pull request Sep 19, 2023
chore: bump Rust to 1.72.1 and cargo update denoland/deno#20572
Merged

scottmcm mentioned this pull request Sep 24, 2023
don't use read_unaligned to read from an array casted to *const Simdrust-lang/portable-simd#341
Open

fintelia mentioned this pull request Sep 27, 2023
Using std::simd to speed-up unfilter for Paeth for bpp=3 and bpp=6 image-rs/image-png#414
Merged

saethlin mentioned this pull request Nov 4, 2023
Suboptimal machine code mapping results or options #117551
Closed

steffahn mentioned this pull request Feb 26, 2025
Miscompilation caused by incorrectly-deduced readonly on virtual call #137646
Closed

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Stop emitting non-power-of-two vectors in (non-portable-SIMD) codegen - #115236

Stop emitting non-power-of-two vectors in (non-portable-SIMD) codegen#115236
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Overall result: no relevant changes - no action needed

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