1; RUN: opt < %s -S -passes=simplifycfg | FileCheck %s 2 3; When SimplifyCFG changes the PHI node into a select instruction, the debug 4; information becomes ambiguous. It causes the debugger to display wrong 5; variable value. 6; 7; When in the debugger, on the line "if (read == 4)", the value of "result" 8; is reported as '2', where it should be zero. 9 10; IR generated with: 11; clang -S -g -O2 -emit-llvm pr38763.cpp -o pr38763.ll -mllvm -opt-bisect-limit=10 12 13; // pr38763.cpp 14; int main() { 15; volatile int foo = 4; 16; int read = foo; 17; int read1 = foo; 18; 19; int result = 0; 20; if (read == 4) { 21; result = read1 + 2; 22; } else { 23; result = read1 - 2; 24; } 25; 26; return result; 27; } 28 29; Remove the '@llvm.dbg.value' associated with 'result' for the true/false 30; branches, as they becomes ambiguous. 31 32; CHECK-LABEL: entry 33; CHECK: %cmp = icmp eq i32 %foo.0., 4, !dbg !14 34; CHECK: %add = add nsw i32 %foo.0.4, 2, !dbg !16 35; CHECK-NOT: #dbg_value(i32 %add 36; CHECK: %sub = add nsw i32 %foo.0.4, -2, !dbg !16 37; CHECK-NOT: #dbg_value(i32 %sub 38; CHECK: %result.0 = select i1 %cmp, i32 %add, i32 %sub 39; CHECK: #dbg_value(i32 %result.0, !12, !DIExpression(), !13 40 41; ModuleID = 'pr38763.cpp' 42source_filename = "pr38763.cpp" 43target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" 44target triple = "x86_64-pc-linux-gnu" 45 46; Function Attrs: norecurse nounwind uwtable 47define dso_local i32 @main() local_unnamed_addr #0 !dbg !7 { 48entry: 49 %foo = alloca i32, align 4 50 store volatile i32 4, ptr %foo, align 4 51 %foo.0. = load volatile i32, ptr %foo, align 4 52 %foo.0.4 = load volatile i32, ptr %foo, align 4 53 call void @llvm.dbg.value(metadata i32 0, metadata !16, metadata !DIExpression()), !dbg !27 54 %cmp = icmp eq i32 %foo.0., 4, !dbg !28 55 br i1 %cmp, label %if.then, label %if.else, !dbg !30 56 57if.then: ; preds = %entry 58 %add = add nsw i32 %foo.0.4, 2, !dbg !31 59 call void @llvm.dbg.value(metadata i32 %add, metadata !16, metadata !DIExpression()), !dbg !27 60 br label %if.end 61 62if.else: ; preds = %entry 63 %sub = add nsw i32 %foo.0.4, -2, !dbg !34 64 call void @llvm.dbg.value(metadata i32 %sub, metadata !16, metadata !DIExpression()), !dbg !27 65 br label %if.end 66 67if.end: ; preds = %if.else, %if.then 68 %result.0 = phi i32 [ %add, %if.then ], [ %sub, %if.else ] 69 call void @llvm.dbg.value(metadata i32 %result.0, metadata !16, metadata !DIExpression()), !dbg !27 70 ret i32 %result.0 71} 72 73; Function Attrs: nounwind readnone speculatable 74declare void @llvm.dbg.value(metadata, metadata, metadata) #2 75 76!llvm.dbg.cu = !{!0} 77!llvm.module.flags = !{!3, !4, !5} 78!llvm.ident = !{!6} 79 80!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) 81!1 = !DIFile(filename: "pr38763.cpp", directory: ".") 82!2 = !{} 83!3 = !{i32 2, !"Dwarf Version", i32 4} 84!4 = !{i32 2, !"Debug Info Version", i32 3} 85!5 = !{i32 1, !"wchar_size", i32 4} 86!6 = !{!"clang version 8.0.0 (trunk 342209)"} 87!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) 88!8 = !DISubroutineType(types: !9) 89!9 = !{!10} 90!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) 91!11 = !{!16} 92!16 = !DILocalVariable(name: "result", scope: !7, file: !1, line: 6, type: !10) 93!27 = !DILocation(line: 6, column: 7, scope: !7) 94!28 = !DILocation(line: 7, column: 12, scope: !29) 95!29 = distinct !DILexicalBlock(scope: !7, file: !1, line: 7, column: 7) 96!30 = !DILocation(line: 7, column: 7, scope: !7) 97!31 = !DILocation(line: 8, column: 20, scope: !32) 98!32 = distinct !DILexicalBlock(scope: !29, file: !1, line: 7, column: 18) 99!34 = !DILocation(line: 10, column: 20, scope: !35) 100!35 = distinct !DILexicalBlock(scope: !29, file: !1, line: 9, column: 10) 101