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[KeyInstr][Clang] For stmt atom (#134646)
This patch is part of a stack that teaches Clang to generate Key Instructions metadata for C and C++. RFC: 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.
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‎clang/lib/CodeGen/CGStmt.cpp

Lines changed: 18 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1365,7 +1365,14 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
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BoolCondVal = emitCondLikelihoodViaExpectIntrinsic(
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BoolCondVal, Stmt::getLikelihood(S.getBody()));
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1368-
Builder.CreateCondBr(BoolCondVal, ForBody, ExitBlock, Weights);
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auto *I = Builder.CreateCondBr(BoolCondVal, ForBody, ExitBlock, Weights);
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// Key Instructions: Emit the condition and branch as separate atoms to
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// match existing loop stepping behaviour. FIXME: We could have the branch
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// as the backup location for the condition, which would probably be a
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// better experience (no jumping to the brace).
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if (auto *CondI = dyn_cast<llvm::Instruction>(BoolCondVal))
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addInstToNewSourceAtom(CondI, nullptr);
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addInstToNewSourceAtom(I, nullptr);
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13701377
if (ExitBlock != LoopExit.getBlock()) {
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EmitBlock(ExitBlock);
@@ -1390,6 +1397,10 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
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EmitStmt(S.getBody());
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}
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// The last block in the loop's body (which unconditionally branches to the
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// `inc` block if there is one).
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auto *FinalBodyBB = Builder.GetInsertBlock();
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// If there is an increment, emit it next.
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if (S.getInc()) {
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EmitBlock(Continue.getBlock());
@@ -1419,6 +1430,12 @@ void CodeGenFunction::EmitForStmt(const ForStmt &S,
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14201431
if (CGM.shouldEmitConvergenceTokens())
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ConvergenceTokenStack.pop_back();
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if (FinalBodyBB) {
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// Key Instructions: We want the for closing brace to be step-able on to
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// match existing behaviour.
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addInstToNewSourceAtom(FinalBodyBB->getTerminator(), nullptr);
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}
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}
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void

‎clang/test/DebugInfo/KeyInstructions/for.c

Lines changed: 145 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,145 @@
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// RUN: %clang_cc1 -triple x86_64-linux-gnu -gkey-instructions -x c++ %s -debug-info-kind=line-tables-only -emit-llvm -o - \
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// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
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// RUN: %clang_cc1 -triple x86_64-linux-gnu -gkey-instructions -x c %s -debug-info-kind=line-tables-only -emit-llvm -o - \
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// RUN: | FileCheck %s --implicit-check-not atomGroup --implicit-check-not atomRank
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// Perennial question: should the inc be its own source atom or not
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// (currently it is).
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// TODO: See do.c and while.c regarding cmp and cond br groups.
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void a(int A) {
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// CHECK: entry:
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// CHECK: store i32 0, ptr %i{{.*}}, !dbg [[G1R1:!.*]]
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// CHECK: for.cond:
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// CHECK: %cmp = icmp slt i32 %0, %1, !dbg [[G2R1:!.*]]
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// CHECK: br i1 %cmp, label %for.body, label %for.end, !dbg [[G3R1:!.*]]
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// TODO: The unconditional br is given an atom group here which is useful for
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// O0. Since we're no longer targeting O0 we should reevaluate whether this
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// adds any value.
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// CHECK: for.body:
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// CHECK-NEXT: br label %for.inc, !dbg [[G5R1:!.*]]
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// CHECK: for.inc:
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// CHECK: %inc = add{{.*}}, !dbg [[G4R2:!.*]]
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// CHECK: store i32 %inc, ptr %i{{.*}}, !dbg [[G4R1:!.*]]
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for (int i = 0; i < A; ++i) {
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}
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}
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void b(int A) {
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// CHECK: entry:
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// CHECK: store i32 0, ptr %i{{.*}}, !dbg [[bG1R1:!.*]]
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// CHECK: for.cond:
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// CHECK: %cmp = icmp slt i32 %0, %1, !dbg [[bG2R1:!.*]]
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// CHECK: br i1 %cmp, label %for.body, label %for.end, !dbg [[bG3R1:!.*]]
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// CHECK: for.body:
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// CHECK-NEXT: %2 = load i32, ptr %A.addr
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// - If stmt atom:
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// CHECK-NEXT: %cmp1 = icmp sgt i32 %2, 1, !dbg [[bG4R2:!.*]]
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// CHECK-NEXT: br i1 %cmp1, label %if.then, label %if.end, !dbg [[bG4R1:!.*]]
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// CHECK: if.then:
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// CHECK-NEXT: br label %if.end
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// - For closing brace.
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// CHECK: if.end:
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// CHECK-NEXT: br label %for.inc, !dbg [[bG6R1:!.*]]
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// CHECK: for.inc:
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// CHECK: %inc = add{{.*}}, !dbg [[bG5R2:!.*]]
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// CHECK: store i32 %inc, ptr %i{{.*}}, !dbg [[bG5R1:!.*]]
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for (int i = 0; i < A; ++i) {
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if (A > 1)
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;
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}
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}
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void c(int A) {
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// CHECK: entry:
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// CHECK: for.cond:
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// CHECK-NEXT: %0 = load i32, ptr %A.addr
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// - If stmt atom:
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// CHECK-NEXT: %cmp = icmp sgt i32 %0, 1, !dbg [[cG1R2:!.*]]
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// CHECK-NEXT: br i1 %cmp, label %if.then, label %if.end, !dbg [[cG1R1:!.*]]
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// CHECK: if.then:
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// CHECK-NEXT: br label %if.end
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// - For closing brace.
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// CHECK: if.end:
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// CHECK-NEXT: br label %for.inc, !dbg [[cG3R1:!.*]]
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// CHECK: for.inc:
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// CHECK-NEXT: %1 = load i32, ptr %A.addr
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// CHECK-NEXT: %inc = add{{.*}}, !dbg [[cG2R2:!.*]]
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// CHECK-NEXT: store i32 %inc, ptr %A.addr{{.*}}, !dbg [[cG2R1:!.*]]
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for (; /*no cond*/ ; ++A) {
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if (A > 1)
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;
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}
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}
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void d() {
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// - Check the `for` keyword gets an atom group.
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// CHECK: entry:
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// CHECK-NEXT: br label %for.cond
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// CHECK: for.cond:
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// CHECK: br label %for.cond, !dbg [[dG1R1:!.*]], !llvm.loop
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for ( ; ; )
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{
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}
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}
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int x, i;
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void ee();
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void e() {
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// - Check we assign an atom group to `for.body`s `br`, even without braces.
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// - TODO: Investigate whether this is needed.
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// CHECK: entry:
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// CHECK: for.cond:
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// CHECK-NEXT: %0 = load i32, ptr @i
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// CHECK-NEXT: %cmp = icmp slt i32 %0, 3, !dbg [[eG1R1:!.*]]
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// CHECK-NEXT: br i1 %cmp, label %for.body, label %for.end, !dbg [[eG2R1:!.*]]
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// CHECK: for.body:
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// CHECK-NEXT: %1 = load i32, ptr @i{{.*}}, !dbg [[eG3R2:!.*]]
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// CHECK-NEXT: store i32 %1, ptr @x{{.*}}, !dbg [[eG3R1:!.*]]
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// CHECK-NEXT: br label %for.inc, !dbg [[eG4R1:!.*]]
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for (; i < 3; ee())
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x = i;
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}
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// CHECK: [[G1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
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// CHECK: [[G2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
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// CHECK: [[G3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
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// CHECK: [[G5R1]] = !DILocation(line: 29,{{.*}} atomGroup: 5, atomRank: 1)
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// CHECK: [[G4R2]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 2)
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// CHECK: [[G4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)
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// CHECK: [[bG1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
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// CHECK: [[bG2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
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// CHECK: [[bG3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
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// CHECK: [[bG4R2]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 2)
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// CHECK: [[bG4R1]] = !DILocation({{.*}}, atomGroup: 4, atomRank: 1)
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// CHECK: [[bG6R1]] = !DILocation(line: 57,{{.*}} atomGroup: 6, atomRank: 1)
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// CHECK: [[bG5R2]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 2)
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// CHECK: [[bG5R1]] = !DILocation({{.*}}, atomGroup: 5, atomRank: 1)
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// CHECK: [[cG1R2]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 2)
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// CHECK: [[cG1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
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// CHECK: [[cG3R1]] = !DILocation(line: 81,{{.*}} atomGroup: 3, atomRank: 1)
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// CHECK: [[cG2R2]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 2)
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// CHECK: [[cG2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
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// CHECK: [[dG1R1]] = !DILocation(line: 91, column: 3, scope: ![[#]], atomGroup: 1, atomRank: 1)
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// CHECK: [[eG1R1]] = !DILocation({{.*}}, atomGroup: 1, atomRank: 1)
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// CHECK: [[eG2R1]] = !DILocation({{.*}}, atomGroup: 2, atomRank: 1)
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// CHECK: [[eG3R2]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 2)
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// CHECK: [[eG3R1]] = !DILocation({{.*}}, atomGroup: 3, atomRank: 1)
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// CHECK: [[eG4R1]] = !DILocation(line: 113, column: 5, scope: ![[#]], atomGroup: 4, atomRank: 1)

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