mirrors/llvm-project
0
0
Fork 0
mirror of https://github.com/llvm/llvm-project.git synced 2025-04-14 15:56:32 +00:00
Code Issues Projects Releases Wiki Activity

[KeyInstr][Clang] For stmt atom

Browse Source 
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 19:12:47 +01:00
parent 38f3eec43e
commit 375ca9f7b7
2 changed files with 53 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
clang/lib/CodeGen/CGStmt.cpp
View File

@ -1324,6 +1324,7 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
Continue = getJumpDestInCurrentScope("for.inc");
BreakContinueStack.push_back(BreakContinue(LoopExit, Continue));
llvm::BasicBlock *ForBody = nullptr;
if (S.getCond()) {
// If the for statement has a condition scope, emit the local variable
// declaration.
@ -1348,7 +1349,7 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
ExitBlock = createBasicBlock("for.cond.cleanup");
// As long as the condition is true, iterate the loop.
llvm::BasicBlock *ForBody = createBasicBlock("for.body");
ForBody = createBasicBlock("for.body");
// C99 6.8.5p2/p4: The first substatement is executed if the expression
// compares unequal to 0. The condition must be a scalar type.
@ -1362,7 +1363,14 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
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 (no jumping to the brace).
if (auto *I = dyn_cast<llvm::Instruction>(BoolCondVal))
addInstToNewSourceAtom(I, nullptr);
addInstToNewSourceAtom(I, nullptr);
if (ExitBlock != LoopExit.getBlock()) {
EmitBlock(ExitBlock);
@ -1416,6 +1424,12 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
if (CGM.shouldEmitConvergenceTokens())
ConvergenceTokenStack.pop_back();
if (ForBody) {
// Key Instructions: We want the for closing brace to be step-able on to
// match existing behaviour.
addInstToNewSourceAtom(ForBody->getTerminator(), nullptr);
}
}
void

37
clang/test/KeyInstructions/for.c Normal file
View File

@ -0,0 +1,37 @@
// RUN: %clang -gkey-instructions -x c++ %s -gmlt -S -emit-llvm -o - \
// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
// RUN: %clang -gkey-instructions -x c %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.
void a(int A) {
// CHECK: entry:
// CHECK: store i32 0, ptr %i{{.*}}, !dbg [[G1R1:!.*]]
// CHECK: for.cond:
// CHECK: %cmp = icmp slt i32 %0, %1, !dbg [[G2R1:!.*]]
// CHECK: br i1 %cmp, label %for.body, label %for.end, !dbg [[G3R1:!.*]]
// FIXME: Added uncond br group here which is useful for O0, which we're
// no longer targeting. With optimisations loop rotate puts the condition
// into for.inc and simplifycfg smooshes that and for.body together, so
// it's not clear whether it adds any value.
// CHECK: for.body:
// CHECK: br label %for.inc, !dbg [[G5R1:!.*]]
// CHECK: for.inc:
// CHECK: %inc = add{{.*}}, !dbg [[G4R2:!.*]]
// CHECK: store i32 %inc, ptr %i{{.*}}, !dbg [[G4R1:!.*]]
for (int i = 0; i < A; ++i) { }
}
// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
// CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
// CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
// CHECK: [[G5R1]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 1)
// CHECK: [[G4R2]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 2)
// CHECK: [[G4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)