Index: include/llvm/Transforms/Utils/Local.h =================================================================== --- include/llvm/Transforms/Utils/Local.h +++ include/llvm/Transforms/Utils/Local.h @@ -443,6 +443,9 @@ void copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI, MDNode *N, LoadInst &NewLI); +/// Remove the debug intrinsic instructions for the given instruction. +void dropDebugUsers(Instruction &I); + //===----------------------------------------------------------------------===// // Intrinsic pattern matching // Index: lib/Transforms/Utils/Local.cpp =================================================================== --- lib/Transforms/Utils/Local.cpp +++ lib/Transforms/Utils/Local.cpp @@ -2522,6 +2522,13 @@ } } +void llvm::dropDebugUsers(Instruction &I) { + SmallVector DbgUsers; + findDbgUsers(DbgUsers, &I); + for (auto *DII : DbgUsers) + DII->eraseFromParent(); +} + namespace { /// A potential constituent of a bitreverse or bswap expression. See Index: lib/Transforms/Utils/SimplifyCFG.cpp =================================================================== --- lib/Transforms/Utils/SimplifyCFG.cpp +++ lib/Transforms/Utils/SimplifyCFG.cpp @@ -2370,15 +2370,19 @@ // Move all 'aggressive' instructions, which are defined in the // conditional parts of the if's up to the dominating block. if (IfBlock1) { - for (auto &I : *IfBlock1) + for (auto &I : *IfBlock1) { I.dropUnknownNonDebugMetadata(); + dropDebugUsers(I); + } DomBlock->getInstList().splice(InsertPt->getIterator(), IfBlock1->getInstList(), IfBlock1->begin(), IfBlock1->getTerminator()->getIterator()); } if (IfBlock2) { - for (auto &I : *IfBlock2) + for (auto &I : *IfBlock2) { I.dropUnknownNonDebugMetadata(); + dropDebugUsers(I); + } DomBlock->getInstList().splice(InsertPt->getIterator(), IfBlock2->getInstList(), IfBlock2->begin(), IfBlock2->getTerminator()->getIterator()); Index: test/CodeGen/X86/pr38763.ll =================================================================== --- test/CodeGen/X86/pr38763.ll +++ test/CodeGen/X86/pr38763.ll @@ -0,0 +1,103 @@ +; RUN: opt < %s -S -simplifycfg | FileCheck %s + +; When SimplifyCFG changes the PHI node into a select instruction, the debug +; information becomes ambiguous. It causes the debugger to display wrong +; variable value. +; +; When in the debugger, on the line "if (read == 4)", the value of "result" +; is reported as '2', where it should be zero. + +; IR generated with: +; clang -S -g -O2 -emit-llvm pr38763.cpp -o pr38763.ll -mllvm -opt-bisect-limit=10 + +; // pr38763.cpp +; int main() { +; volatile int foo = 4; +; int read = foo; +; int read1 = foo; +; +; int result = 0; +; if (read == 4) { +; result = read1 + 2; +; } else { +; result = read1 - 2; +; } +; +; return result; +; } + +; Remove the '@llvm.dbg.value' associated with 'result' for the true/false +; branches, as they becomes ambiguous. + +; CHECK-LABEL: entry +; CHECK: %cmp = icmp eq i32 %foo.0., 4 +; CHECK: %add = add nsw i32 %foo.0.4, 2, !dbg !18 +; CHECK-NOT: @llvm.dbg.value(metadata i32 %add +; CHECK: %sub = add nsw i32 %foo.0.4, -2, !dbg !21 +; CHECK-NOT: @llvm.dbg.value(metadata i32 %sub +; CHECK: %result.0 = select i1 %cmp, i32 %add, i32 %sub +; CHECK: call void @llvm.dbg.value(metadata i32 %result.0, metadata !12, metadata !DIExpression()), !dbg !17 + +; ModuleID = 'pr38763.cpp' +source_filename = "pr38763.cpp" +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-pc-linux-gnu" + +; Function Attrs: norecurse nounwind uwtable +define dso_local i32 @main() local_unnamed_addr #0 !dbg !7 { +entry: + %foo = alloca i32, align 4 + %foo.0..sroa_cast = bitcast i32* %foo to i8* + store volatile i32 4, i32* %foo, align 4, !tbaa !19 + %foo.0. = load volatile i32, i32* %foo, align 4 + %foo.0.4 = load volatile i32, i32* %foo, align 4 + call void @llvm.dbg.value(metadata i32 0, metadata !16, metadata !DIExpression()), !dbg !27 + %cmp = icmp eq i32 %foo.0., 4 + br i1 %cmp, label %if.then, label %if.else + +if.then: ; preds = %entry + %add = add nsw i32 %foo.0.4, 2, !dbg !31 + call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !27 + br label %if.end + +if.else: ; preds = %entry + %sub = add nsw i32 %foo.0.4, -2, !dbg !34 + call void @llvm.dbg.value(metadata i32 %sub, metadata !16, metadata !DIExpression()), !dbg !27 + br label %if.end + +if.end: ; preds = %if.else, %if.then + %result.0 = phi i32 [ %add, %if.then ], [ %sub, %if.else ] + call void @llvm.dbg.value(metadata i32 %result.0, metadata !16, metadata !DIExpression()), !dbg !27 + ret i32 %result.0 +} + +; Function Attrs: nounwind readnone speculatable +declare void @llvm.dbg.value(metadata, metadata, metadata) #2 + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4, !5} +!llvm.ident = !{!6} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (trunk 342209)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None) +!1 = !DIFile(filename: "pr38763.cpp", directory: ".") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{i32 1, !"wchar_size", i32 4} +!6 = !{!"clang version 8.0.0 (trunk 342209)"} +!7 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11) +!8 = !DISubroutineType(types: !9) +!9 = !{!10} +!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!11 = !{!16} +!16 = !DILocalVariable(name: "result", scope: !7, file: !1, line: 6, type: !10) +!19 = !{!20, !20, i64 0} +!20 = !{!"int", !21, i64 0} +!21 = !{!"omnipotent char", !22, i64 0} +!22 = !{!"Simple C++ TBAA"} +!27 = !DILocation(line: 6, column: 7, scope: !7) +!29 = distinct !DILexicalBlock(scope: !7, file: !1, line: 7, column: 7) +!31 = !DILocation(line: 8, column: 20, scope: !32) +!32 = distinct !DILexicalBlock(scope: !29, file: !1, line: 7, column: 18) +!34 = !DILocation(line: 10, column: 20, scope: !35) +!35 = distinct !DILexicalBlock(scope: !29, file: !1, line: 9, column: 10)