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[KeyInstr][Clang] For range stmt atoms

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This patch is part of a stack that teaches Clang to generate Key Instructions
metadata for C and C++.

The Key Instructions project is introduced, including a "quick summary" section
at the top which adds context for this PR, here:
https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668

The feature is only functional in LLVM if LLVM is built with CMake flag
LLVM_EXPERIMENTAL_KEY_INSTRUCTIONs. Eventually that flag will be removed.

The Clang-side work is demoed here:
https://github.com/llvm/llvm-project/pull/130943
This commit is contained in:
Orlando Cazalet-Hyams 2025-04-03 19:46:01 +01:00
parent 375ca9f7b7
commit 2484a49c8f
2 changed files with 84 additions and 1 deletions
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13
clang/lib/CodeGen/CGStmt.cpp
View File

@ -1477,7 +1477,14 @@ CodeGenFunction::EmitCXXForRangeStmt(const CXXForRangeStmt &S,
if (!Weights && CGM.getCodeGenOpts().OptimizationLevel)
BoolCondVal = emitCondLikelihoodViaExpectIntrinsic(
BoolCondVal, Stmt::getLikelihood(S.getBody()));
Builder.CreateCondBr(BoolCondVal, ForBody, ExitBlock, Weights);
auto *I = Builder.CreateCondBr(BoolCondVal, ForBody, ExitBlock, Weights);
// Key Instructions: Emit the condition and branch as separate atoms to
// match existing loop stepping behaviour. FIXME: We could have the branch as
// the backup location for the condition, which would probably be a better
// experience.
if (auto *I = dyn_cast<llvm::Instruction>(BoolCondVal))
addInstToNewSourceAtom(I, nullptr);
addInstToNewSourceAtom(I, nullptr);
if (ExitBlock != LoopExit.getBlock()) {
EmitBlock(ExitBlock);
@ -1526,6 +1533,10 @@ CodeGenFunction::EmitCXXForRangeStmt(const CXXForRangeStmt &S,
if (CGM.shouldEmitConvergenceTokens())
ConvergenceTokenStack.pop_back();
// We want the for closing brace to be step-able on to match existing
// behaviour.
addInstToNewSourceAtom(ForBody->getTerminator(), nullptr);
}
void CodeGenFunction::EmitReturnOfRValue(RValue RV, QualType Ty) {

72
clang/test/KeyInstructions/for-range.cpp Normal file
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@ -0,0 +1,72 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
// RUN: %clang -gkey-instructions %s -gmlt -S -emit-llvm -o - \
// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
// Perennial quesiton: should the inc be its own source atom or not
// (currently it is).
// FIXME: See do.c and while.c regarding cmp and cond br groups.
// The stores in the setup (stores to __RANGE1, __BEGIN1, __END1) are all
// marked as Key. Unclear whether that's desirable. Keep for now as that's
// least risky.
// Check the conditional branch (and the condition) in FOR_COND and
// unconditional branch in FOR_BODY are Key Instructions.
struct Range {
int *begin();
int *end();
} r;
// CHECK-LABEL: define dso_local void @_Z1av(
// CHECK-SAME: ) #[[ATTR0:[0-9]+]] !dbg [[DBG10:![0-9]+]] {
// CHECK-NEXT: [[ENTRY:.*:]]
// CHECK-NEXT: [[__RANGE1:%.*]] = alloca ptr, align 8
// CHECK-NEXT: [[__BEGIN1:%.*]] = alloca ptr, align 8
// CHECK-NEXT: [[__END1:%.*]] = alloca ptr, align 8
// CHECK-NEXT: [[I:%.*]] = alloca i32, align 4
// CHECK-NEXT: store ptr @r, ptr [[__RANGE1]], align 8, !dbg [[DBG14:![0-9]+]]
// CHECK-NEXT: [[CALL:%.*]] = call noundef ptr @_ZN5Range5beginEv(ptr noundef nonnull align 1 dereferenceable(1) @r), !dbg [[DBG15:![0-9]+]]
// CHECK-NEXT: store ptr [[CALL]], ptr [[__BEGIN1]], align 8, !dbg [[DBG16:![0-9]+]]
// CHECK-NEXT: [[CALL1:%.*]] = call noundef ptr @_ZN5Range3endEv(ptr noundef nonnull align 1 dereferenceable(1) @r), !dbg [[DBG17:![0-9]+]]
// CHECK-NEXT: store ptr [[CALL1]], ptr [[__END1]], align 8, !dbg [[DBG18:![0-9]+]]
// CHECK-NEXT: br label %[[FOR_COND:.*]], !dbg [[DBG19:![0-9]+]]
// CHECK: [[FOR_COND]]:
// CHECK-NEXT: [[TMP0:%.*]] = load ptr, ptr [[__BEGIN1]], align 8, !dbg [[DBG19]]
// CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr [[__END1]], align 8, !dbg [[DBG19]]
// CHECK-NEXT: [[CMP:%.*]] = icmp ne ptr [[TMP0]], [[TMP1]], !dbg [[DBG20:![0-9]+]]
// CHECK-NEXT: br i1 [[CMP]], label %[[FOR_BODY:.*]], label %[[FOR_END:.*]], !dbg [[DBG21:![0-9]+]]
// CHECK: [[FOR_BODY]]:
// CHECK-NEXT: [[TMP2:%.*]] = load ptr, ptr [[__BEGIN1]], align 8, !dbg [[DBG19]]
// CHECK-NEXT: [[TMP3:%.*]] = load i32, ptr [[TMP2]], align 4, !dbg [[DBG22:![0-9]+]]
// CHECK-NEXT: store i32 [[TMP3]], ptr [[I]], align 4, !dbg [[DBG23:![0-9]+]]
// CHECK-NEXT: br label %[[FOR_INC:.*]], !dbg [[DBG24:![0-9]+]]
// CHECK: [[FOR_INC]]:
// CHECK-NEXT: [[TMP4:%.*]] = load ptr, ptr [[__BEGIN1]], align 8, !dbg [[DBG19]]
// CHECK-NEXT: [[INCDEC_PTR:%.*]] = getelementptr inbounds nuw i32, ptr [[TMP4]], i32 1, !dbg [[DBG25:![0-9]+]]
// CHECK-NEXT: store ptr [[INCDEC_PTR]], ptr [[__BEGIN1]], align 8, !dbg [[DBG26:![0-9]+]]
// CHECK-NEXT: br label %[[FOR_COND]], !dbg [[DBG19]], !llvm.loop
// CHECK: [[FOR_END]]:
// CHECK-NEXT: ret void, !dbg [[DBG30:![0-9]+]]
//
void a() {
for (int i: r)
;
}
//.
// CHECK: [[DBG14]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
// CHECK: [[DBG15]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
// CHECK: [[DBG16]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
// CHECK: [[DBG17]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
// CHECK: [[DBG18]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
// CHECK: [[DBG19]] = !DILocation({{.*}})
// CHECK: [[DBG20]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)
// CHECK: [[DBG21]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 1)
// CHECK: [[DBG22]] = !DILocation({{.*}}, atomGroup: 6, atomRank: 2)
// CHECK: [[DBG23]] = !DILocation({{.*}}, atomGroup: 6, atomRank: 1)
// CHECK: [[DBG24]] = !DILocation({{.*}} atomGroup: 8, atomRank: 1)
// CHECK: [[DBG25]] = !DILocation({{.*}}, atomGroup: 7, atomRank: 2)
// CHECK: [[DBG26]] = !DILocation({{.*}}, atomGroup: 7, atomRank: 1)
// CHECK: [[DBG30]] = !DILocation({{.*}})
//.