Index: llvm/lib/Transforms/Scalar/BDCE.cpp =================================================================== --- llvm/lib/Transforms/Scalar/BDCE.cpp +++ llvm/lib/Transforms/Scalar/BDCE.cpp @@ -101,7 +101,7 @@ (I.getType()->isIntOrIntVectorTy() && DB.getDemandedBits(&I).isNullValue() && wouldInstructionBeTriviallyDead(&I))) { - salvageDebugInfo(I); + salvageDebugInfoOrMarkUndef(I); Worklist.push_back(&I); I.dropAllReferences(); Changed = true; Index: llvm/test/Transforms/BDCE/pr41925.ll =================================================================== --- /dev/null +++ llvm/test/Transforms/BDCE/pr41925.ll @@ -0,0 +1,118 @@ +; Check for setting dbg.value undef which depends on instruction which is going to be dead +; RUN: opt -bdce %s -S | FileCheck %s +@b = common dso_local local_unnamed_addr global i8 0, align 1, !dbg !0 +@a = common dso_local local_unnamed_addr global i8 0, align 1, !dbg !6 + +; Function Attrs: noinline nounwind uwtable +define dso_local i32 @main() local_unnamed_addr #0 !dbg !13 { +entry: +;CHECK: call void @llvm.dbg.value(metadata i8 2 +;CHECK: call void @llvm.dbg.value(metadata i8 2 + call void @llvm.dbg.value(metadata i8 2, metadata !17, metadata !DIExpression()), !dbg !18 + %.pr = load i8, i8* @b, align 1, !dbg !19 + call void @llvm.dbg.value(metadata i8 2, metadata !17, metadata !DIExpression()), !dbg !18 + %cmp5 = icmp slt i8 %.pr, 1, !dbg !22 + br i1 %cmp5, label %for.cond2thread-pre-split.preheader, label %for.end9, !dbg !23 + +for.cond2thread-pre-split.preheader: ; preds = %entry + br label %for.cond2thread-pre-split, !dbg !23 +for.cond2thread-pre-split: ; preds = %for.cond2thread-pre-split.preheader, %for.inc7 +;CHECK: call void @llvm.dbg.value(metadata i8 undef + %l_177.06 = phi i8 [ %l_177.1.lcssa, %for.inc7 ], [ 2, %for.cond2thread-pre-split.preheader ] + call void @llvm.dbg.value(metadata i8 %l_177.06, metadata !17, metadata !DIExpression()), !dbg !18 +;CHECK: call void @llvm.dbg.value(metadata i8 undef + %.pr1 = load i8, i8* @a, align 1, !dbg !24 + call void @llvm.dbg.value(metadata i8 %l_177.06, metadata !17, metadata !DIExpression()), !dbg !18 + %cmp42 = icmp sgt i8 %.pr1, -1, !dbg !27 + br i1 %cmp42, label %for.body6.preheader, label %for.inc7, !dbg !28 + +for.body6.preheader: ; preds = %for.cond2thread-pre-split + br label %for.body6, !dbg !28 + +for.body6: ; preds = %for.body6.preheader, %for.body6 +;CHECK: call void @llvm.dbg.value(metadata i8 undef +;CHECK: call void @llvm.dbg.value(metadata i8 undef + %l_177.13 = phi i8 [ %inc, %for.body6 ], [ %l_177.06, %for.body6.preheader ] + call void @llvm.dbg.value(metadata i8 %l_177.13, metadata !17, metadata !DIExpression()), !dbg !18 + call void @llvm.dbg.value(metadata i8 %l_177.13, metadata !17, metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_stack_value)), !dbg !18 + tail call void (...) @optimize_me_not() #3, !dbg !29 + %inc = add i8 %l_177.13, 1, !dbg !31 + %0 = load i8, i8* @a, align 1, !dbg !32 + %dec = add i8 %0, -1, !dbg !32 + store i8 %dec, i8* @a, align 1, !dbg !32 + call void @llvm.dbg.value(metadata i8 %inc, metadata !17, metadata !DIExpression()), !dbg !18 + %cmp4 = icmp sgt i8 %dec, -1, !dbg !27 + br i1 %cmp4, label %for.body6, label %for.inc7.loopexit, !dbg !28, !llvm.loop !33 + +for.inc7.loopexit: ; preds = %for.body6 + %inc.lcssa = phi i8 [ %inc, %for.body6 ], !dbg !31 + br label %for.inc7, !dbg !35 + +for.inc7: ; preds = %for.inc7.loopexit, %for.cond2thread-pre-split +;CHECK: call void @llvm.dbg.value(metadata i8 undef + %l_177.1.lcssa = phi i8 [ %l_177.06, %for.cond2thread-pre-split ], [ %inc.lcssa, %for.inc7.loopexit ], !dbg !18 + %1 = load i8, i8* @b, align 1, !dbg !35 + %inc8 = add i8 %1, 1, !dbg !35 + store i8 %inc8, i8* @b, align 1, !dbg !35 + call void @llvm.dbg.value(metadata i8 %l_177.1.lcssa, metadata !17, metadata !DIExpression()), !dbg !18 + %cmp = icmp slt i8 %inc8, 1, !dbg !22 + br i1 %cmp, label %for.cond2thread-pre-split, label %for.end9.loopexit, !dbg !23, !llvm.loop !36 + +for.end9.loopexit: ; preds = %for.inc7 + br label %for.end9, !dbg !38 + +for.end9: ; preds = %for.end9.loopexit, %entry + ret i32 0, !dbg !38 +} + +declare dso_local void @optimize_me_not(...) local_unnamed_addr + +declare void @llvm.dbg.value(metadata, metadata, metadata) #1 + +attributes #0 = { noinline nounwind uwtable } +attributes #1 = { nounwind readnone speculatable willreturn } +attributes #3 = { nounwind } + +!llvm.dbg.cu = !{!2} +!llvm.module.flags = !{!9, !10, !11} +!llvm.ident = !{!12} + +!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression()) +!1 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 3, type: !8, isLocal: false, isDefinition: true) +!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None) +!3 = !DIFile(filename: "test", directory: "test") +!4 = !{} +!5 = !{!6, !0} +!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression()) +!7 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 3, type: !8, isLocal: false, isDefinition: true) +!8 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char) +!9 = !{i32 2, !"Dwarf Version", i32 4} +!10 = !{i32 2, !"Debug Info Version", i32 3} +!11 = !{i32 1, !"wchar_size", i32 4} +!12 = !{!"clang version 10.0.0"} +!13 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 4, type: !14, scopeLine: 4, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !4) +!14 = !DISubroutineType(types: !15) +!15 = !{!16} +!16 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!17 = !DILocalVariable(name: "l_177", scope: !13, file: !3, line: 5, type: !8) +!18 = !DILocation(line: 0, scope: !13) +!19 = !DILocation(line: 6, column: 10, scope: !20) +!20 = distinct !DILexicalBlock(scope: !21, file: !3, line: 6, column: 3) +!21 = distinct !DILexicalBlock(scope: !13, file: !3, line: 6, column: 3) +!22 = !DILocation(line: 6, column: 12, scope: !20) +!23 = !DILocation(line: 6, column: 3, scope: !21) +!24 = !DILocation(line: 7, column: 12, scope: !25) +!25 = distinct !DILexicalBlock(scope: !26, file: !3, line: 7, column: 5) +!26 = distinct !DILexicalBlock(scope: !20, file: !3, line: 7, column: 5) +!27 = !DILocation(line: 7, column: 14, scope: !25) +!28 = !DILocation(line: 7, column: 5, scope: !26) +!29 = !DILocation(line: 9, column: 7, scope: !30) +!30 = distinct !DILexicalBlock(scope: !25, file: !3, line: 7, column: 25) +!31 = !DILocation(line: 8, column: 7, scope: !30) +!32 = !DILocation(line: 7, column: 21, scope: !25) +!33 = distinct !{!33, !28, !34} +!34 = !DILocation(line: 10, column: 5, scope: !26) +!35 = !DILocation(line: 6, column: 19, scope: !20) +!36 = distinct !{!36, !23, !37} +!37 = !DILocation(line: 10, column: 5, scope: !21) +!38 = !DILocation(line: 11, column: 1, scope: !13)