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[ctxprof] Don't lower instrumentation for noreturn functions #134932

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Merged
merged 1 commit into from
Apr 8, 2025
Merged

[ctxprof] Don't lower instrumentation for noreturn functions #134932

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12 changes: 12 additions & 0 deletions llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
//

#include "llvm/Transforms/Instrumentation/PGOCtxProfLowering.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/CtxProfAnalysis.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/Analysis.h"
Expand Down Expand Up @@ -206,6 +207,17 @@ PreservedAnalyses PGOCtxProfLoweringPass::run(Module &M,
bool CtxInstrumentationLowerer::lowerFunction(Function &F) {
if (F.isDeclaration())
return false;

// Probably pointless to try to do anything here, unlikely to be
// performance-affecting.
if (F.doesNotReturn()) {
for (auto &BB : F)
for (auto &I : make_early_inc_range(BB))
if (isa<InstrProfCntrInstBase>(&I))
I.eraseFromParent();
return true;
}

auto &FAM = MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(F);

Expand Down
22 changes: 19 additions & 3 deletions llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -310,11 +310,26 @@ define void @has_musttail_calls() {
musttail call void @bar()
ret void
}

define void @does_not_return() noreturn {
; INSTRUMENT-LABEL: define void @does_not_return(
; INSTRUMENT-SAME: ) #[[ATTR0:[0-9]+]] {
; INSTRUMENT-NEXT: call void @llvm.instrprof.increment(ptr @does_not_return, i64 742261418966908927, i32 1, i32 0)
; INSTRUMENT-NEXT: unreachable
;
; LOWERING-LABEL: define void @does_not_return(
; LOWERING-SAME: ) #[[ATTR0:[0-9]+]] !guid [[META8:![0-9]+]] {
; LOWERING-NEXT: unreachable
;
unreachable
}
;.
; LOWERING: attributes #[[ATTR0:[0-9]+]] = { nounwind }
; LOWERING: attributes #[[ATTR1:[0-9]+]] = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
; LOWERING: attributes #[[ATTR0]] = { noreturn }
; LOWERING: attributes #[[ATTR1:[0-9]+]] = { nounwind }
; LOWERING: attributes #[[ATTR2:[0-9]+]] = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
;.
; INSTRUMENT: attributes #[[ATTR0:[0-9]+]] = { nounwind }
; INSTRUMENT: attributes #[[ATTR0]] = { noreturn }
; INSTRUMENT: attributes #[[ATTR1:[0-9]+]] = { nounwind }
;.
; LOWERING: [[META0]] = !{i64 6699318081062747564}
; LOWERING: [[META1]] = !{i64 4909520559318251808}
Expand All @@ -324,4 +339,5 @@ define void @has_musttail_calls() {
; LOWERING: [[META5]] = !{i64 5458232184388660970}
; LOWERING: [[META6]] = !{i64 -3771893999295659109}
; LOWERING: [[META7]] = !{i64 -4680624981836544329}
; LOWERING: [[META8]] = !{i64 5519225910966780583}
;.
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