diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -3857,10 +3857,18 @@ // here, but that computation has been sunk. SmallVector DbgUsers; findDbgUsers(DbgUsers, I); - // Process the sinking DbgUsers in reverse order, as we only want to clone the - // last appearing debug intrinsic for each given variable. + + // For all debug values in the destination block, the sunk instruction + // will still be available, so they do not need to be dropped. + SmallVector DbgUsersToSalvage; + for (auto &DbgUser : DbgUsers) + if (DbgUser->getParent() != DestBlock) + DbgUsersToSalvage.push_back(DbgUser); + + // Process the sinking DbgUsersToSalvage in reverse order, as we only want + // to clone the last appearing debug intrinsic for each given variable. SmallVector DbgUsersToSink; - for (DbgVariableIntrinsic *DVI : DbgUsers) + for (DbgVariableIntrinsic *DVI : DbgUsersToSalvage) if (DVI->getParent() == SrcBlock) DbgUsersToSink.push_back(DVI); llvm::sort(DbgUsersToSink, @@ -3896,7 +3904,7 @@ // Perform salvaging without the clones, then sink the clones. if (!DIIClones.empty()) { - salvageDebugInfoForDbgValues(*I, DbgUsers); + salvageDebugInfoForDbgValues(*I, DbgUsersToSalvage); // The clones are in reverse order of original appearance, reverse again to // maintain the original order. for (auto &DIIClone : llvm::reverse(DIIClones)) { diff --git a/llvm/test/Transforms/InstCombine/sink-instruction-introduces-unnecessary-poison-value.ll b/llvm/test/Transforms/InstCombine/sink-instruction-introduces-unnecessary-poison-value.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/InstCombine/sink-instruction-introduces-unnecessary-poison-value.ll @@ -0,0 +1,91 @@ +; RUN: opt -passes=instcombine -S -o - < %s | FileCheck %s + +; When the 'int Four = Two;' is sunk into the 'case 0:' block, +; the debug value for 'Three' is set incorrectly to 'poison'. + +; 1 int One = 0; +; 2 int Two = 0; +; 3 int test() { +; 4 int Three = 0; +; 5 int Four = Two; +; 6 switch (One) { +; 7 case 0: +; 8 Three = Four; +; 9 break; +; 10 case 2: +; 11 Three = 4; +; 12 break; +; 13 } +; 14 return Three; +; 15 } + +; CHECK-LABEL: sw.bb: +; CHECK: %[[REG:[0-9]+]] = load i32, ptr @"?Two{{.*}} +; CHECK: call void @llvm.dbg.value(metadata i32 %[[REG]], metadata ![[DBG1:[0-9]+]], {{.*}} +; CHECK: call void @llvm.dbg.value(metadata i32 %[[REG]], metadata ![[DBG2:[0-9]+]], {{.*}} +; CHECK-DAG: ![[DBG1]] = !DILocalVariable(name: "Four"{{.*}}) +; CHECK-DAG: ![[DBG2]] = !DILocalVariable(name: "Three"{{.*}}) + +@"?One@@3HA" = dso_local global i32 0, align 4, !dbg !0 +@"?Two@@3HA" = dso_local global i32 0, align 4, !dbg !5 + +define dso_local noundef i32 @"?test@@YAHXZ"() !dbg !15 { +entry: + call void @llvm.dbg.value(metadata i32 0, metadata !19, metadata !DIExpression()), !dbg !20 + %0 = load i32, ptr @"?Two@@3HA", align 4, !dbg !21 + call void @llvm.dbg.value(metadata i32 %0, metadata !22, metadata !DIExpression()), !dbg !20 + %1 = load i32, ptr @"?One@@3HA", align 4, !dbg !23 + switch i32 %1, label %sw.epilog [ + i32 0, label %sw.bb + i32 2, label %sw.bb1 + ], !dbg !23 + +sw.bb: ; preds = %entry + call void @llvm.dbg.value(metadata i32 %0, metadata !19, metadata !DIExpression()), !dbg !20 + br label %sw.epilog, !dbg !24 + +sw.bb1: ; preds = %entry + call void @llvm.dbg.value(metadata i32 4, metadata !19, metadata !DIExpression()), !dbg !20 + br label %sw.epilog, !dbg !26 + +sw.epilog: ; preds = %sw.bb1, %sw.bb, %entry + %Three.0 = phi i32 [ 0, %entry ], [ 4, %sw.bb1 ], [ %0, %sw.bb ], !dbg !20 + call void @llvm.dbg.value(metadata i32 %Three.0, metadata !19, metadata !DIExpression()), !dbg !20 + ret i32 %Three.0, !dbg !27 +} + +declare void @llvm.dbg.declare(metadata, metadata, metadata) +declare void @llvm.dbg.value(metadata, metadata, metadata) + +!llvm.dbg.cu = !{!2} +!llvm.module.flags = !{!8, !9, !10, !11, !12, !13} +!llvm.ident = !{!14} + +!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression()) +!1 = distinct !DIGlobalVariable(name: "One", linkageName: "?One@@3HA", scope: !2, file: !3, line: 1, type: !7, isLocal: false, isDefinition: true) +!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 18.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None) +!3 = !DIFile(filename: "test.cpp", directory: "") +!4 = !{!0, !5} +!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression()) +!6 = distinct !DIGlobalVariable(name: "Two", linkageName: "?Two@@3HA", scope: !2, file: !3, line: 2, type: !7, isLocal: false, isDefinition: true) +!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!8 = !{i32 2, !"CodeView", i32 1} +!9 = !{i32 2, !"Debug Info Version", i32 3} +!10 = !{i32 1, !"wchar_size", i32 2} +!11 = !{i32 8, !"PIC Level", i32 2} +!12 = !{i32 7, !"uwtable", i32 2} +!13 = !{i32 1, !"MaxTLSAlign", i32 65536} +!14 = !{!"clang version 18.0.0"} +!15 = distinct !DISubprogram(name: "test", linkageName: "?test@@YAHXZ", scope: !3, file: !3, line: 3, type: !16, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !18) +!16 = !DISubroutineType(types: !17) +!17 = !{!7} +!18 = !{} +!19 = !DILocalVariable(name: "Three", scope: !15, file: !3, line: 4, type: !7) +!20 = !DILocation(line: 0, scope: !15) +!21 = !DILocation(line: 5, scope: !15) +!22 = !DILocalVariable(name: "Four", scope: !15, file: !3, line: 5, type: !7) +!23 = !DILocation(line: 6, scope: !15) +!24 = !DILocation(line: 9, scope: !25) +!25 = distinct !DILexicalBlock(scope: !15, file: !3, line: 6) +!26 = !DILocation(line: 12, scope: !25) +!27 = !DILocation(line: 14, scope: !15)