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[KeyInstr][Clang] If stmt atom

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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 18:05:07 +01:00
parent 638b319d13
commit 98ea64f7a1
3 changed files with 58 additions and 0 deletions
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2
clang/lib/CodeGen/CodeGenFunction.cpp
View File

@ -2099,6 +2099,8 @@ void CodeGenFunction::EmitBranchOnBoolExpr(
llvm::Instruction *BrInst = Builder.CreateCondBr(CondV, TrueBlock, FalseBlock,
Weights, Unpredictable);
addInstToNewSourceAtom(BrInst, CondV);
switch (HLSLControlFlowAttr) {
case HLSLControlFlowHintAttr::Microsoft_branch:
case HLSLControlFlowHintAttr::Microsoft_flatten: {

10
clang/lib/CodeGen/CodeGenFunction.h
View File

@ -1768,6 +1768,16 @@ public:
DI->addInstToCurrentSourceAtom(KeyInstruction, Backup);
}
/// Add \p KeyInstruction and an optional \p Backup instruction to a new atom
/// group (See ApplyAtomGroup for more info).
void addInstToNewSourceAtom(llvm::Instruction *KeyInstruction,
llvm::Value *Backup) {
if (CGDebugInfo *DI = getDebugInfo()) {
ApplyAtomGroup Grp(getDebugInfo());
DI->addInstToCurrentSourceAtom(KeyInstruction, Backup);
}
}
/// See CGDebugInfo::addRetToOverrideOrNewSourceAtom.
void addRetToOverrideOrNewSourceAtom(llvm::ReturnInst *Ret,
llvm::Value *Backup) {

46
clang/test/KeyInstructions/if.c Normal file
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@ -0,0 +1,46 @@
// RUN: %clang -gkey-instructions -x c++ -std=c++17 %s -gmlt -S -emit-llvm -o - \
// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank --check-prefixes=CHECK,CHECK-CXX
// RUN: %clang -gkey-instructions -x c %s -gmlt -S -emit-llvm -o - \
// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
int g;
void a(int A) {
// The branch is a key instruction, with the condition being its backup.
// CHECK: entry:
// CHECK: %tobool = icmp ne i32 %0, 0{{.*}}, !dbg [[G1R2:!.*]]
// CHECK: br i1 %tobool, label %if.then, label %if.end{{.*}}, !dbg [[G1R1:!.*]]
if (A)
;
// The assignment in the if gets a distinct source atom group.
// CHECK: if.end:
// CHECK: %1 = load i32, ptr %A.addr{{.*}}, !dbg [[G2R2:!.*]]
// CHECK: store i32 %1, ptr @g{{.*}}, !dbg [[G2R1:!.*]]
// CHECK: %tobool1 = icmp ne i32 %1, 0{{.*}}, !dbg [[G3R2:!.*]]
// CHECK: br i1 %tobool1, label %if.then2, label %if.end3{{.*}}, !dbg [[G3R1:!.*]]
if ((g = A))
;
#ifdef __cplusplus
// The assignment in the if gets a distinct source atom group.
// CHECK-CXX: if.end3:
// CHECK-CXX: %2 = load i32, ptr %A.addr{{.*}}, !dbg [[G4R2:!.*]]
// CHECK-CXX: store i32 %2, ptr %B{{.*}}, !dbg [[G4R1:!.*]]
// CHECK-CXX: %tobool4 = icmp ne i32 %3, 0{{.*}}, !dbg [[G5R2:!.*]]
// CHECK-CXX: br i1 %tobool4, label %if.then5, label %if.end6{{.*}}, !dbg [[G5R1:!.*]]
if (int B = A; B)
;
#endif
}
// CHECK: [[G1R2]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 2)
// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
// CHECK: [[G2R2]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
// CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
// CHECK: [[G3R2]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
// CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
// CHECK-CXX: [[G4R2]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 2)
// CHECK-CXX: [[G4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)
// CHECK-CXX: [[G5R2]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 2)
// CHECK-CXX: [[G5R1]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 1)