[ctxprof] Don't lower instrumentation for noreturn functions
#134932
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@llvm/pr-subscribers-pgo Author: Mircea Trofin (mtrofin) ChangesFull diff: https://github.com/llvm/llvm-project/pull/134932.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
index 2f8d7766bb588..a314457423819 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
@@ -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"
@@ -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);
diff --git a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
index 75f292deb71c2..8f72711a9c8b1 100644
--- a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
+++ b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
@@ -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}
@@ -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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@llvm/pr-subscribers-llvm-transforms Author: Mircea Trofin (mtrofin) ChangesFull diff: https://github.com/llvm/llvm-project/pull/134932.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
index 2f8d7766bb588..a314457423819 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
@@ -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"
@@ -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);
diff --git a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
index 75f292deb71c2..8f72711a9c8b1 100644
--- a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
+++ b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
@@ -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}
@@ -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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ilovepi
approved these changes
Apr 8, 2025
Merge activity
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mtrofin
deleted the
users/mtrofin/04-08-_ctxprof_don_t_lower_instrumentation_for_noreturn_functions
branch
var-const
pushed a commit
to ldionne/llvm-project
that referenced
this pull request
Apr 17, 2025
…134932) `noreturn` functions are doubtfully interesting for performance optimization / profiling.
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noreturnfunctions are doubtfully interesting for performance optimization / profiling.