https://github.com/mtrofin updated
https://github.com/llvm/llvm-project/pull/135651
>From ea629230ae6202ed34122cecb7ebce20ccffad19 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtro...@google.com>
Date: Mon, 14 Apr 2025 10:03:55 -0700
Subject: [PATCH] [ctxprof] Extend the notion of "cannot return"
---
.../Instrumentation/PGOCtxProfLowering.cpp | 19 ++++++++------
.../ctx-instrumentation-invalid-roots.ll | 25 +++++++++++--------
.../PGOProfile/ctx-instrumentation.ll | 15 ++++++++++-
3 files changed, 41 insertions(+), 18 deletions(-)
diff --git a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
index f99d7b9d03e02..136225ab27cdc 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOCtxProfLowering.cpp
@@ -9,6 +9,7 @@
#include "llvm/Transforms/Instrumentation/PGOCtxProfLowering.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/CtxProfAnalysis.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/Analysis.h"
@@ -105,6 +106,12 @@ std::pair<uint32_t, uint32_t>
getNumCountersAndCallsites(const Function &F) {
}
return {NumCounters, NumCallsites};
}
+
+void emitUnsupportedRoot(const Function &F, StringRef Reason) {
+ F.getContext().emitError("[ctxprof] The function " + F.getName() +
+ " was indicated as context root but " + Reason +
+ ", which is not supported.");
+}
} // namespace
// set up tie-in with compiler-rt.
@@ -164,12 +171,8 @@
CtxInstrumentationLowerer::CtxInstrumentationLowerer(Module &M,
for (const auto &BB : *F)
for (const auto &I : BB)
if (const auto *CB = dyn_cast<CallBase>(&I))
- if (CB->isMustTailCall()) {
- M.getContext().emitError("The function " + Fname +
- " was indicated as a context root, "
- "but it features musttail "
- "calls, which is not supported.");
- }
+ if (CB->isMustTailCall())
+ emitUnsupportedRoot(*F, "it features musttail calls");
}
}
@@ -230,11 +233,13 @@ bool CtxInstrumentationLowerer::lowerFunction(Function
&F) {
// Probably pointless to try to do anything here, unlikely to be
// performance-affecting.
- if (F.doesNotReturn()) {
+ if (!llvm::canReturn(F)) {
for (auto &BB : F)
for (auto &I : make_early_inc_range(BB))
if (isa<InstrProfCntrInstBase>(&I))
I.eraseFromParent();
+ if (ContextRootSet.contains(&F))
+ emitUnsupportedRoot(F, "it does not return");
return true;
}
diff --git
a/llvm/test/Transforms/PGOProfile/ctx-instrumentation-invalid-roots.ll
b/llvm/test/Transforms/PGOProfile/ctx-instrumentation-invalid-roots.ll
index 454780153b823..b5ceb4602c60b 100644
--- a/llvm/test/Transforms/PGOProfile/ctx-instrumentation-invalid-roots.ll
+++ b/llvm/test/Transforms/PGOProfile/ctx-instrumentation-invalid-roots.ll
@@ -1,17 +1,22 @@
-; RUN: not opt -passes=ctx-instr-gen,ctx-instr-lower
-profile-context-root=good \
-; RUN: -profile-context-root=bad \
-; RUN: -S < %s 2>&1 | FileCheck %s
+; RUN: split-file %s %t
+; RUN: not opt -passes=ctx-instr-gen,ctx-instr-lower
-profile-context-root=the_func -S %t/musttail.ll -o - 2>&1 | FileCheck %s
+; RUN: not opt -passes=ctx-instr-gen,ctx-instr-lower
-profile-context-root=the_func -S %t/unreachable.ll -o - 2>&1 | FileCheck %s
+; RUN: not opt -passes=ctx-instr-gen,ctx-instr-lower
-profile-context-root=the_func -S %t/noreturn.ll -o - 2>&1 | FileCheck %s
+;--- musttail.ll
declare void @foo()
-define void @good() {
- call void @foo()
- ret void
-}
-
-define void @bad() {
+define void @the_func() {
musttail call void @foo()
ret void
}
+;--- unreachable.ll
+define void @the_func() {
+ unreachable
+}
+;--- noreturn.ll
+define void @the_func() noreturn {
+ unreachable
+}
-; CHECK: error: The function bad was indicated as a context root, but it
features musttail calls, which is not supported.
+; CHECK: error: [ctxprof] The function the_func was indicated as context root
diff --git a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
index 6b2f25a585ec3..6afa37ef286f5 100644
--- a/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
+++ b/llvm/test/Transforms/PGOProfile/ctx-instrumentation.ll
@@ -18,7 +18,7 @@ declare void @bar()
; LOWERING: @[[GLOB4:[0-9]+]] = internal global { ptr, ptr, ptr, ptr, i8 }
zeroinitializer
; LOWERING: @[[GLOB5:[0-9]+]] = internal global { ptr, ptr, ptr, ptr, i8 }
zeroinitializer
; LOWERING: @[[GLOB6:[0-9]+]] = internal global { ptr, ptr, ptr, ptr, i8 }
zeroinitializer
-; LOWERING: @[[GLOB7:[0-9]+]] = internal global { ptr, ptr, ptr, ptr, i8 } {
ptr null, ptr null, ptr inttoptr (i64 1 to ptr), ptr null, i8 0 }
+; LOWERING: @[[GLOB7:[0-9]+]] = internal global { ptr, ptr, ptr, ptr, i8 }
zeroinitializer
;.
define void @foo(i32 %a, ptr %fct) {
; INSTRUMENT-LABEL: define void @foo(
@@ -323,6 +323,18 @@ define void @does_not_return() noreturn {
;
unreachable
}
+
+define void @unreachable() {
+; INSTRUMENT-LABEL: define void @unreachable() {
+; INSTRUMENT-NEXT: call void @llvm.instrprof.increment(ptr @unreachable,
i64 742261418966908927, i32 1, i32 0)
+; INSTRUMENT-NEXT: unreachable
+;
+; LOWERING-LABEL: define void @unreachable(
+; LOWERING-SAME: ) !guid [[META9:![0-9]+]] {
+; LOWERING-NEXT: unreachable
+;
+ unreachable
+}
;.
; LOWERING: attributes #[[ATTR0]] = { noreturn }
; LOWERING: attributes #[[ATTR1:[0-9]+]] = { nounwind }
@@ -340,4 +352,5 @@ define void @does_not_return() noreturn {
; LOWERING: [[META6]] = !{i64 -3771893999295659109}
; LOWERING: [[META7]] = !{i64 -4680624981836544329}
; LOWERING: [[META8]] = !{i64 5519225910966780583}
+; LOWERING: [[META9]] = !{i64 -565652589829076809}
;.
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