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Calculate predecessor count directly #138076

Merged
merged 2 commits into from
Mar 13, 2025
Merged

Calculate predecessor count directly #138076

merged 2 commits into from
Mar 13, 2025

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tmiasko
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@tmiasko tmiasko commented Mar 5, 2025

Avoid allocating a vector of small vectors merely to determine how many
predecessors each basic block has.

Additionally use u8 and saturating operations. The pass only needs to
distinguish between [0..1] and [2..].

tmiasko added 2 commits March 6, 2025 00:23
@tmiasko
Remove start block special case
508b803 
Edges to the start block are invalid. The special case is unnecessary.
@tmiasko
Calculate predecessor count directly
5bae3ad 
Avoid allocating a vector of small vectors merely to determine how many
predecessors each basic block has.

Additionally use u8 and saturating operations. The pass only needs to
distinguish between [0..1] and [2..].
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rustbot commented Mar 5, 2025

r? @matthewjasper

rustbot has assigned @matthewjasper.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

@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 Mar 5, 2025
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rustbot commented Mar 5, 2025

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

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tmiasko commented Mar 5, 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 Mar 5, 2025
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 5, 2025
@bors
Auto merge of rust-lang#138076 - tmiasko:pred-count, r=<try>
3c3b10f 
Calculate predecessor count directly

Avoid allocating a vector of small vectors merely to determine how many
predecessors each basic block has.

Additionally use u8 and saturating operations. The pass only needs to
distinguish between [0..1] and [2..].
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bors commented Mar 5, 2025

⌛ Trying commit 5bae3ad with merge 3c3b10f...

tmiasko
tmiasko commented Mar 5, 2025
View reviewed changes
compiler/rustc_mir_transform/src/add_call_guards.rs
@@ -32,9 +32,12 @@ pub(super) use self::AddCallGuards::*;

impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let mut pred_count: IndexVec<_, _> =
body.basic_blocks.predecessors().iter().map(|ps| ps.len()).collect();
pred_count[START_BLOCK] += 1;
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Start block has no predecessors since #88968, so this special case is no longer necessary.

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bors commented Mar 6, 2025

💥 Test timed out

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tmiasko commented Mar 6, 2025

@bors try

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bors commented Mar 6, 2025

⌛ Trying commit 5bae3ad with merge b7f0f0d...

bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 6, 2025
@bors
Auto merge of rust-lang#138076 - tmiasko:pred-count, r=<try>
b7f0f0d 
Calculate predecessor count directly

Avoid allocating a vector of small vectors merely to determine how many
predecessors each basic block has.

Additionally use u8 and saturating operations. The pass only needs to
distinguish between [0..1] and [2..].
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bors commented Mar 6, 2025

💔 Test failed - checks-actions

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 6, 2025
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tmiasko commented Mar 6, 2025

@bors try

bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 6, 2025
@bors
Auto merge of rust-lang#138076 - tmiasko:pred-count, r=<try>
5b8ba42 
Calculate predecessor count directly

Avoid allocating a vector of small vectors merely to determine how many
predecessors each basic block has.

Additionally use u8 and saturating operations. The pass only needs to
distinguish between [0..1] and [2..].
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bors commented Mar 6, 2025

⌛ Trying commit 5bae3ad with merge 5b8ba42...

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bors commented Mar 6, 2025

☀️ Try build successful - checks-actions
Build commit: 5b8ba42 (5b8ba42668c1190c3ada8568aee9619f086f9242)

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Finished benchmarking commit (5b8ba42): comparison URL.

Overall result: no relevant changes - 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 benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -2.1%, secondary -1.5%)

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)		 1.2% [1.2%, 1.2%] 1
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -5.4% [-5.4%, -5.4%] 1
Improvements ✅
(secondary)		 -1.5% [-2.3%, -0.7%] 2
All ❌✅ (primary) -2.1% [-5.4%, 1.2%] 2

Cycles

Results (secondary 0.6%)

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)		 2.0% [1.9%, 2.1%] 3
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -3.6% [-3.6%, -3.6%] 1
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 773.363s -> 773.423s (0.01%)
Artifact size: 362.14 MiB -> 362.12 MiB (-0.00%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Mar 6, 2025
@tmiasko tmiasko added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 6, 2025
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@bors r+

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bors commented Mar 12, 2025

📌 Commit 5bae3ad has been approved by matthewjasper

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 Mar 12, 2025
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bors commented Mar 12, 2025

⌛ Testing commit 5bae3ad with merge 0e76f8b...

@bors bors mentioned this pull request Mar 13, 2025
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bors commented Mar 13, 2025

☀️ Test successful - checks-actions
Approved by: matthewjasper
Pushing 0e76f8b to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 13, 2025
@bors bors merged commit 0e76f8b into rust-lang:master Mar 13, 2025
7 checks passed
@rustbot rustbot added this to the 1.87.0 milestone Mar 13, 2025
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Post-merge analysis result

Test differences

No test diffs found

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Finished benchmarking commit (0e76f8b): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -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)		 0.6% [0.6%, 0.6%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) - - 0

Max RSS (memory usage)

Results (primary 2.3%, secondary 6.0%)

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)		 2.3% [2.3%, 2.3%] 1
Regressions ❌
(secondary)		 6.0% [6.0%, 6.0%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 2.3% [2.3%, 2.3%] 1

Cycles

Results (secondary -2.1%)

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)		 -2.1% [-2.1%, -2.1%] 1
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 777.224s -> 777.49s (0.03%)
Artifact size: 365.30 MiB -> 365.33 MiB (0.01%)

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