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Use llvm.memset.p0i8.* to initialize all same-bytes arrays #135258

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merged 4 commits into from
Jan 11, 2025
Merged

Use llvm.memset.p0i8.* to initialize all same-bytes arrays #135258

merged 4 commits into from
Jan 11, 2025

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oli-obk
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@oli-obk oli-obk commented Jan 8, 2025 •
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Similar to #43488

debug builds can now handle 0x0101_u16 and other multi-byte scalars that have all the same bytes (instead of special casing just 0)

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rustbot commented Jan 8, 2025

r? @saethlin

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@rustbot 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 Jan 8, 2025
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oli-obk commented Jan 8, 2025

@bors try @rust-timer queue

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jan 8, 2025
@oli-obk oli-obk force-pushed the push-ktzskvxuwnlt branch from 32099f0 to bed8b95 Compare January 8, 2025 15:44
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@oli-obk oli-obk force-pushed the push-ktzskvxuwnlt branch from bed8b95 to 3ca023e Compare January 8, 2025 16:56
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oli-obk commented Jan 8, 2025

@bors try @rust-timer queue

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bors commented Jan 8, 2025

⌛ Trying commit 3ca023e with merge 7ed3665...

bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 8, 2025
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Auto merge of rust-lang#135258 - oli-obk:push-ktzskvxuwnlt, r=<try>
7ed3665 
Use llvm.memset.p0i8.* to initialize all same-bytes arrays

It doesn't affect tests, LLVM seems smart enough for it, but then I wonder why we have the zero case at all (it was introduced in rust-lang#43488, maybe LLVM wasn't smart enough then). So let's run perf to see if there's any build time effect, and if no, I'll remove the zero special case and also run perf.
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bors commented Jan 8, 2025

☀️ Try build successful - checks-actions
Build commit: 7ed3665 (7ed366534d90da69be91456384caf3738966680a)

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Finished benchmarking commit (7ed3665): comparison URL.

Overall result: ❌ regressions - 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 the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

mean range count
Regressions ❌
(primary)		 - - 0
Regressions ❌
(secondary)		 0.3% [0.3%, 0.3%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) - - 0

Max RSS (memory usage)

Results (primary 5.2%, secondary -2.5%)

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)		 5.2% [2.0%, 8.3%] 2
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -2.5% [-2.5%, -2.5%] 1
All ❌✅ (primary) 5.2% [2.0%, 8.3%] 2

Cycles

Results (primary -1.9%, secondary -3.3%)

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)		 -1.9% [-3.4%, -0.6%] 12
Improvements ✅
(secondary)		 -3.3% [-3.8%, -2.2%] 3
All ❌✅ (primary) -1.9% [-3.4%, -0.6%] 12

Binary size

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

Bootstrap: 763.722s -> 763.396s (-0.04%)
Artifact size: 325.68 MiB -> 325.71 MiB (0.01%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jan 8, 2025
@oli-obk oli-obk force-pushed the push-ktzskvxuwnlt branch from 3ca023e to 45070ce Compare January 9, 2025 09:24
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Looks good!

r=me if you want to tweak the commit history here or the PR description :)

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oli-obk commented Jan 10, 2025

@bors r=saethlin

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bors commented Jan 10, 2025

📌 Commit 280fbdb has been approved by saethlin

It is now in the queue for this repository.

@bors 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 Jan 10, 2025
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oli-obk commented Jan 10, 2025

@bors r=saethlin

removed a FIXME that was fixed by this PR

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bors commented Jan 10, 2025

📌 Commit 65b01cb has been approved by saethlin

It is now in the queue for this repository.

@oli-obk oli-obk mentioned this pull request Jan 10, 2025
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 10, 2025
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Auto merge of rust-lang#135335 - oli-obk:push-zxwssomxxtnq, r=<try>
ca1798b 
Treat undef bytes as equal to any other byte

Basically since `undef` can be any byte, it can also be the byte(s) that are in the non-undef parts of a value. So we can just treat the `undef` at not being there and only look at the initialized bytes and memset over them

fixes rust-lang#104290

based on rust-lang#135258
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bors commented Jan 11, 2025

⌛ Testing commit 65b01cb with merge a2d7c81...

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bors commented Jan 11, 2025

☀️ Test successful - checks-actions
Approved by: saethlin
Pushing a2d7c81 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 11, 2025
@bors bors merged commit a2d7c81 into rust-lang:master Jan 11, 2025
7 checks passed
@rustbot rustbot added this to the 1.86.0 milestone Jan 11, 2025
bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 11, 2025
@bors
Auto merge of rust-lang#135335 - oli-obk:push-zxwssomxxtnq, r=<try>
cabcef2 
Treat undef bytes as equal to any other byte

Basically since `undef` can be any byte, it can also be the byte(s) that are in the non-undef parts of a value. So we can just treat the `undef` at not being there and only look at the initialized bytes and memset over them

fixes rust-lang#104290

based on rust-lang#135258
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Finished benchmarking commit (a2d7c81): 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 -1.7%, secondary 3.0%)

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)		 3.0% [3.0%, 3.0%] 1
Improvements ✅
(primary)		 -1.7% [-1.7%, -1.7%] 1
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) -1.7% [-1.7%, -1.7%] 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: 764.863s -> 763.776s (-0.14%)
Artifact size: 325.94 MiB -> 326.00 MiB (0.02%)

@oli-obk oli-obk deleted the push-ktzskvxuwnlt branch January 11, 2025 09:17
bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 21, 2025
@bors
Auto merge of rust-lang#135335 - oli-obk:push-zxwssomxxtnq, r=saethlin
663dd5e 
codegen: store ScalarPair via memset when one side is undef and the other side can be memset

Basically since `undef` can be any byte, it can also be the byte(s) that are in the non-undef parts of a value. So we can just treat the `undef` at not being there and only look at the initialized bytes and memset over them

fixes rust-lang#104290

based on rust-lang#135258
bors added a commit to rust-lang-ci/rust that referenced this pull request Jan 21, 2025
@bors
Auto merge of rust-lang#135335 - oli-obk:push-zxwssomxxtnq, r=saethlin
a7a6c64 
codegen: store ScalarPair via memset when one side is undef and the other side can be memset

Basically since `undef` can be any byte, it can also be the byte(s) that are in the non-undef parts of a value. So we can just treat the `undef` at not being there and only look at the initialized bytes and memset over them

fixes rust-lang#104290

based on rust-lang#135258
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