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[DebugInfo][ConstraintElimination] Fix debug value loss in replacing comparisons with the speculated constants (#136839)
Fix #135736
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‎llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DebugInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
@@ -1457,8 +1458,29 @@ static bool checkAndReplaceCondition(
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return ShouldReplace;
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});
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NumCondsRemoved++;
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// Update the debug value records that satisfy the same condition used
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// in replaceUsesWithIf.
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SmallVector<DbgVariableIntrinsic *> DbgUsers;
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SmallVector<DbgVariableRecord *> DVRUsers;
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findDbgUsers(DbgUsers, Cmp, &DVRUsers);
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for (auto *DVR : DVRUsers) {
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auto *DTN = DT.getNode(DVR->getParent());
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if (!DTN || DTN->getDFSNumIn() < NumIn || DTN->getDFSNumOut() > NumOut)
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continue;
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auto *MarkedI = DVR->getInstruction();
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if (MarkedI->getParent() == ContextInst->getParent() &&
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MarkedI->comesBefore(ContextInst))
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continue;
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DVR->replaceVariableLocationOp(Cmp, ConstantC);
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}
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if (Cmp->use_empty())
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ToRemove.push_back(Cmp);
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return Changed;
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};
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‎llvm/test/Transforms/ConstraintElimination/salvage-dbg-values-replaced-by-constant-2.ll

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; RUN: opt < %s -passes=constraint-elimination -S | FileCheck %s
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; Check that checkAndReplaceCondition() salvages the debug value information after replacing
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; the conditions (`%c.1` and `%t.2` in this test) with the speculated constants (GitHub Issue
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; #135736).
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; In particular, the debug value record uses should not be replaced if they come before the
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; context instrtuction (e.g., `%t.2` in this example).
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declare void @llvm.assume(i1 noundef) #0
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declare void @may_unwind()
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declare void @use(i1)
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define i1 @assume_single_bb_conditions_after_assume(i8 %a, i8 %b, i1 %c) !dbg !5 {
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; CHECK-LABEL: define i1 @assume_single_bb_conditions_after_assume(
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; CHECK: [[CMP_1:%.*]] = icmp ule i8 [[ADD_1:%.*]], [[B:%.*]], !dbg [[DBG12:![0-9]+]]
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; CHECK-NEXT: [[C_1:%.*]] = icmp ule i8 [[ADD_1]], [[B]], !dbg [[DBG13:![0-9]+]]
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; CHECK-NEXT: #dbg_value(i1 [[C_1]], [[META9:![0-9]+]], !DIExpression(), [[META14:![0-9]+]])
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; CHECK-NEXT: call void @use(i1 [[C_1]]), !dbg [[DBG15:![0-9]+]]
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; CHECK-NEXT: #dbg_value(i1 [[C_1]], [[META9]], !DIExpression(), [[META14]])
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; CHECK-NEXT: call void @may_unwind(), !dbg [[DBG16:![0-9]+]]
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; CHECK-NEXT: #dbg_value(i1 [[C_1]], [[META9]], !DIExpression(), [[META14]])
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; CHECK-NEXT: call void @llvm.assume(i1 [[CMP_1]]), !dbg [[DBG17:![0-9]+]]
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; CHECK-NEXT: #dbg_value(i1 [[C_1]], [[META9]], !DIExpression(), [[META14]])
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; CHECK-NEXT: #dbg_value(i1 true, [[META9]], !DIExpression(), [[META14]])
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; CHECK-NEXT: [[RES_1:%.*]] = xor i1 true, true, !dbg [[DBG18:![0-9]+]]
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;
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%add.1 = add nuw nsw i8 %a, 1, !dbg !11
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%cmp.1 = icmp ule i8 %add.1, %b, !dbg !12
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%c.1 = icmp ule i8 %add.1, %b, !dbg !13
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#dbg_value(i1 %c.1, !9, !DIExpression(), !14)
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call void @use(i1 %c.1), !dbg !15
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#dbg_value(i1 %c.1, !9, !DIExpression(), !14)
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call void @may_unwind(), !dbg !16
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#dbg_value(i1 %c.1, !9, !DIExpression(), !14)
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call void @llvm.assume(i1 %cmp.1), !dbg !17
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#dbg_value(i1 %c.1, !9, !DIExpression(), !14)
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%t.2 = icmp ule i8 %a, %b, !dbg !14
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#dbg_value(i1 %c.1, !9, !DIExpression(), !14)
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%res.1 = xor i1 %c.1, %t.2, !dbg !18
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%add.2 = add nuw nsw i8 %a, 2, !dbg !19
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%c.2 = icmp ule i8 %add.2, %b, !dbg !20
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%res.2 = xor i1 %res.1, %c.2, !dbg !21
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ret i1 %res.2, !dbg !22
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}
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attributes #0 = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }
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!llvm.dbg.cu = !{!0}
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!llvm.debugify = !{!2, !3}
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!llvm.module.flags = !{!4}
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!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
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!1 = !DIFile(filename: "/app/example.ll", directory: "/")
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!2 = !{i32 12}
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!3 = !{i32 8}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = distinct !DISubprogram(name: "assume_single_bb_conditions_after_assume", linkageName: "assume_single_bb_conditions_after_assume", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
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!6 = !DISubroutineType(types: !7)
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!7 = !{}
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!8 = !{!9}
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!9 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 7, type: !10)
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!10 = !DIBasicType(name: "ty8", size: 8, encoding: DW_ATE_unsigned)
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!11 = !DILocation(line: 1, column: 1, scope: !5)
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!12 = !DILocation(line: 2, column: 1, scope: !5)
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!13 = !DILocation(line: 3, column: 1, scope: !5)
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!14 = !DILocation(line: 7, column: 1, scope: !5)
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!15 = !DILocation(line: 4, column: 1, scope: !5)
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!16 = !DILocation(line: 5, column: 1, scope: !5)
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!17 = !DILocation(line: 6, column: 1, scope: !5)
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!18 = !DILocation(line: 8, column: 1, scope: !5)
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!19 = !DILocation(line: 9, column: 1, scope: !5)
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!20 = !DILocation(line: 10, column: 1, scope: !5)
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!21 = !DILocation(line: 11, column: 1, scope: !5)
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!22 = !DILocation(line: 12, column: 1, scope: !5)
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; CHECK: [[META9]] = !DILocalVariable(name: "4",
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; CHECK: [[DBG12]] = !DILocation(line: 2, column: 1,
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; CHECK: [[DBG13]] = !DILocation(line: 3, column: 1,
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; CHECK: [[META14]] = !DILocation(line: 7, column: 1,
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; CHECK: [[DBG18]] = !DILocation(line: 8, column: 1,
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;.

‎llvm/test/Transforms/ConstraintElimination/salvage-dbg-values-replaced-by-constant.ll

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; RUN: opt < %s -passes=constraint-elimination -S | FileCheck %s
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; Check that checkAndReplaceCondition() salvages the debug value information after replacing
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; the conditions (`%t.1` in this test) with the speculated constants (GitHub Issue #135736).
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; In particular, debug uses are replaced if the debug record is dominated by the condition fact.
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define i1 @test_and_ule(i4 %x, i4 %y, i4 %z) !dbg !5 {
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; CHECK-LABEL: define i1 @test_and_ule(
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; CHECK-SAME: i4 [[X:%.*]], i4 [[Y:%.*]], i4 [[Z:%.*]])
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; CHECK: [[T_1:%.*]] = icmp ule i4 [[X]], [[Z]], !dbg [[DBG13:![0-9]+]]
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;
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entry:
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%c.1 = icmp ule i4 %x, %y, !dbg !11
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%c.2 = icmp ule i4 %y, %z, !dbg !12
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%t.1 = icmp ule i4 %x, %z, !dbg !13
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%and = and i1 %c.1, %c.2, !dbg !14
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br i1 %and, label %then, label %exit, !dbg !15
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; CHECK: [[THEN:.*]]:
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; CHECK-NEXT: #dbg_value(i1 true, [[META9:![0-9]+]], !DIExpression(), [[DBG13]])
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; CHECK-NEXT: [[R_1:%.*]] = xor i1 true, true, !dbg [[DBG16:![0-9]+]]
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then: ; preds = %entry
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#dbg_value(i1 %t.1, !9, !DIExpression(), !13)
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%r.1 = xor i1 %t.1, %t.1, !dbg !16
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br label %exit
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; CHECK: [[EXIT:.*]]:
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; CHECK-NEXT: #dbg_value(i1 [[T_1]], [[META17:![0-9]+]], !DIExpression(), [[DBG13]])
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; CHECK-NEXT: ret i1 [[T_1]], !dbg [[DBG18:![0-9]+]]
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exit: ; preds = %bb1, %entry
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#dbg_value(i1 %t.1, !17, !DIExpression(), !13)
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ret i1 %t.1, !dbg !18
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}
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!llvm.dbg.cu = !{!0}
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!llvm.debugify = !{!2, !3}
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!llvm.module.flags = !{!4}
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!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
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!1 = !DIFile(filename: "temp.ll", directory: "/")
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!2 = !{i32 20}
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!3 = !{i32 17}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = distinct !DISubprogram(name: "test_and_ule", linkageName: "test_and_ule", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
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!6 = !DISubroutineType(types: !7)
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!7 = !{}
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!8 = !{!9}
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!9 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
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!10 = !DIBasicType(name: "ty8", size: 8, encoding: DW_ATE_unsigned)
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!11 = !DILocation(line: 1, column: 1, scope: !5)
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!12 = !DILocation(line: 2, column: 1, scope: !5)
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!13 = !DILocation(line: 5, column: 1, scope: !5)
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!14 = !DILocation(line: 3, column: 1, scope: !5)
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!15 = !DILocation(line: 4, column: 1, scope: !5)
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!16 = !DILocation(line: 7, column: 1, scope: !5)
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!17 = !DILocalVariable(name: "6", scope: !5, file: !1, line: 7, type: !10)
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!18 = !DILocation(line: 20, column: 1, scope: !5)
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; CHECK: [[META9]] = !DILocalVariable(name: "4",
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; CHECK: [[DBG13]] = !DILocation(line: 5, column: 1,
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; CHECK: [[DBG16]] = !DILocation(line: 7, column: 1,
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; CHECK: [[META17]] = !DILocalVariable(name: "6",
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; CHECK: [[DBG18]] = !DILocation(line: 20, column: 1,
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;.

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