Index: llvm/trunk/lib/Transforms/Scalar/BDCE.cpp =================================================================== --- llvm/trunk/lib/Transforms/Scalar/BDCE.cpp +++ llvm/trunk/lib/Transforms/Scalar/BDCE.cpp @@ -39,6 +39,11 @@ SmallVector Worklist; bool Changed = false; for (Instruction &I : instructions(F)) { + // If the instruction has side effects and no non-dbg uses, + // BDCE should skip it. + if (I.mayHaveSideEffects() && I.use_empty()) + continue; + if (I.getType()->isIntegerTy() && !DB.getDemandedBits(&I).getBoolValue()) { // For live instructions that have all dead bits, first make them dead by Index: llvm/trunk/test/Transforms/BDCE/pr26587.ll =================================================================== --- llvm/trunk/test/Transforms/BDCE/pr26587.ll +++ llvm/trunk/test/Transforms/BDCE/pr26587.ll @@ -0,0 +1,46 @@ +; Test that BDCE doesn't destroy llvm.dbg.value's argument. +; RUN: opt -bdce %s -S | FileCheck %s + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; CHECK: define void @f() +; CHECK-NEXT: entry: +; CHECK-NEXT: tail call void (...) @h() +; CHECK-NEXT: %[[CALL:.*]] = tail call i32 (...) @g() +; CHECK-NEXT: tail call void @llvm.dbg.value(metadata i32 %[[CALL:.*]] + +define void @f() !dbg !6 { +entry: + tail call void (...) @h(), !dbg !9 + %call = tail call i32 (...) @g(), !dbg !10 + tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !11, metadata !13), !dbg !14 + tail call void (...) @h(), !dbg !15 + ret void, !dbg !16 +} + +declare void @h(...) +declare i32 @g(...) +declare void @llvm.dbg.value(metadata, i64, metadata, metadata) + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4} +!llvm.ident = !{!5} + +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2) +!1 = !DIFile(filename: "patatino.c", directory: "/home/davide/work/llvm/build-clang/bin") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{!"clang version 4.0.0 (trunk 288665) (llvm/trunk 288725)"} +!6 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !7, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: false, unit: !0, variables: !2) +!7 = !DISubroutineType(types: !8) +!8 = !{null} +!9 = !DILocation(line: 4, column: 3, scope: !6) +!10 = !DILocation(line: 5, column: 11, scope: !6) +!11 = !DILocalVariable(name: "a", scope: !6, file: !1, line: 5, type: !12) +!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!13 = !DIExpression() +!14 = !DILocation(line: 5, column: 7, scope: !6) +!15 = !DILocation(line: 6, column: 3, scope: !6) +!16 = !DILocation(line: 7, column: 1, scope: !6)