Merge these copy statements that simplified the canonical enum clone method by GVN #129931

DianQK · 2024-09-03T13:44:29Z

This is blocked by #128299.

rustbot · 2024-09-03T13:44:37Z

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DianQK · 2024-09-03T13:45:05Z

r? ghost

rustbot · 2024-09-03T13:45:08Z

Failed to set assignee to ghost: invalid assignee

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DianQK · 2024-09-03T13:46:55Z

r? cjgillot

bors · 2024-09-14T17:07:18Z

☔ The latest upstream changes (presumably #128299) made this pull request unmergeable. Please resolve the merge conflicts.

This reverts commit 25d434b.

…method by GVN

DianQK · 2024-09-14T22:02:59Z

@bors try @rust-timer queue

bors · 2024-09-14T22:04:09Z

⌛ Trying commit 622247a with merge c324112...

Merge these copy statements that simplified the canonical enum clone method by GVN This is blocked by rust-lang#128299.

bors · 2024-09-14T23:56:31Z

☀️ Try build successful - checks-actions
Build commit: c324112 (c3241126e94d7a53a1805ad854686e0bd061b5df)

rust-timer · 2024-09-15T02:22:20Z

Finished benchmarking commit (c324112): 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 0.9%)

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)	4.0%	[3.0%, 5.1%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.8%	[-5.9%, -1.7%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[-5.9%, 5.1%]	5

Cycles

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

Binary size

Results (primary 0.0%, secondary -0.0%)

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)	0.1%	[0.0%, 0.2%]	11
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	2
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.0%]	6
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	3
All ❌✅ (primary)	0.0%	[-0.3%, 0.2%]	17

Bootstrap: 760.71s -> 756.595s (-0.54%)
Artifact size: 341.13 MiB -> 341.17 MiB (0.01%)

cjgillot

My high-level reaction to this PR is that it's both too specific in what it's trying to match (a clone impl) and too general in its implementation (handles storage statements...).

I suggest having two heuristics:

for clone impls, use some kind of StructuralClone trait so that we fully replace the derived impls Clone with simpler MIR;
for general MIR, lift the restrictions on this pass (bb0 and assignment to _0 namely).

What do you think?

cjgillot · 2024-09-15T13:07:59Z

compiler/rustc_mir_transform/src/lib.rs

@@ -604,6 +602,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
            &dead_store_elimination::DeadStoreElimination::Initial,
            &gvn::GVN,
            &simplify::SimplifyLocals::AfterGVN,
+            &match_branches::MatchBranchSimplification,


Should this run on clone shims too? Or do we want a trait-based solution to detect trivial clone impls?

cjgillot · 2024-09-15T13:08:53Z

compiler/rustc_mir_transform/src/match_branches.rs

+            if simplify_to_copy(tcx, body, bb_idx, param_env).is_some() {
+                should_cleanup = true;
+                continue;
+            }


Should this be made a standalone MirPass? This will be easier to have some analyses computed only once.

cjgillot · 2024-09-15T13:12:53Z

compiler/rustc_mir_transform/src/match_branches.rs

+        if stmts.is_empty() {
+            return None;
+        }
+        if let [Statement { kind: StatementKind::Assign(box (place, rvalue)), .. }] =


Could you add a comment for the high-level pattern you are trying to match?

cjgillot · 2024-09-15T13:16:04Z

compiler/rustc_mir_transform/src/match_branches.rs

+                    }
+                }
+            }
+            let expected_copy_stmt = expected_copy_stmt?;


Should we perform the same analysis on this statement that we do in the single statement branch above?

DianQK · 2024-09-18T13:08:45Z

* for clone impls, use some kind of `StructuralClone` trait so that we fully replace the derived impls `Clone` with simpler MIR;

* for general MIR, lift the restrictions on this pass (bb0 and assignment to _0 namely).

What do you think?

It looks like makes sense.
IIUC, the StructuralClone is exact matching clone shims? I expect this can improve compile-time.

@rustbot author

rustbot assigned nnethercote Sep 3, 2024

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 Sep 3, 2024

rustbot assigned cjgillot and unassigned nnethercote Sep 3, 2024

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DianQK force-pushed the match-br-copy branch from efce2e8 to adb6166 Compare September 3, 2024 14:44

DianQK added 2 commits September 15, 2024 05:57

Revert "Update try_question_mark_nop.rs test"

124d12b

This reverts commit 25d434b.

Merge these copy statements that simplified the canonical enum clone …

622247a

…method by GVN

DianQK force-pushed the match-br-copy branch from adb6166 to 622247a Compare September 14, 2024 22:02

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 14, 2024

bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 14, 2024

Auto merge of rust-lang#129931 - DianQK:match-br-copy, r=<try>

c324112

Merge these copy statements that simplified the canonical enum clone method by GVN This is blocked by rust-lang#128299.

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 15, 2024

cjgillot reviewed Sep 15, 2024

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DianQK mentioned this pull request Sep 17, 2024

tests: allow trunc/select instructions to be missing #130454

Merged

rustbot 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 Sep 18, 2024

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Merge these copy statements that simplified the canonical enum clone method by GVN #129931

Merge these copy statements that simplified the canonical enum clone method by GVN #129931

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DianQK commented Sep 18, 2024

Merge these copy statements that simplified the canonical enum clone method by GVN #129931

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Merge these copy statements that simplified the canonical enum clone method by GVN #129931

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rust-timer commented Sep 15, 2024

Overall result: no relevant changes - no action needed

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DianQK commented Sep 18, 2024