Index: llvm/trunk/lib/Transforms/Scalar/GVN.cpp =================================================================== --- llvm/trunk/lib/Transforms/Scalar/GVN.cpp +++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp @@ -1700,7 +1700,10 @@ if (isa(V)) V->takeName(LI); if (Instruction *I = dyn_cast(V)) - if (LI->getDebugLoc()) + // If instruction I has debug info, then we should not update it. + // Also, if I has a null DebugLoc, then it is still potentially incorrect + // to propagate LI's DebugLoc because LI may not post-dominate I. + if (LI->getDebugLoc() && ValuesPerBlock.size() != 1) I->setDebugLoc(LI->getDebugLoc()); if (V->getType()->getScalarType()->isPointerTy()) MD->invalidateCachedPointerInfo(V); Index: llvm/trunk/test/Transforms/GVN/dbg-redundant-load.ll =================================================================== --- llvm/trunk/test/Transforms/GVN/dbg-redundant-load.ll +++ llvm/trunk/test/Transforms/GVN/dbg-redundant-load.ll @@ -0,0 +1,52 @@ +; RUN: opt -gvn -S < %s | FileCheck %s + +; Check that the redundant load from %if.then is removed. +; Also, check that the debug location associated to load %0 still refers to +; line 3 and not line 6. + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" + +; CHECK: @test_redundant_load( +; CHECK-LABEL: entry: +; CHECK-NEXT: load i32, i32* %Y, align 4, !dbg ![[LOC:[0-9]+]] +; CHECK-LABEL: if.then: +; CHECK-NOT: load +; CHECK-LABEL: if.end: +; CHECK: ![[LOC]] = !DILocation(line: 3, scope: !{{.*}}) + +define i32 @test_redundant_load(i32 %X, i32* %Y) !dbg !6 { +entry: + %0 = load i32, i32* %Y, align 4, !dbg !8 + %cmp = icmp sgt i32 %X, -1, !dbg !9 + br i1 %cmp, label %if.then, label %if.end, !dbg !9 + +if.then: ; preds = %entry + %1 = load i32, i32* %Y, align 4, !dbg !10 + %add = add nsw i32 %0, %1, !dbg !10 + call void @foo(), !dbg !11 + br label %if.end, !dbg !12 + +if.end: ; preds = %if.then, %entry + %Result.0 = phi i32 [ %add, %if.then ], [ %0, %entry ] + ret i32 %Result.0, !dbg !13 +} + +declare void @foo() + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4, !5} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2) +!1 = !DIFile(filename: "test.cpp", directory: "") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{i32 1, !"PIC Level", i32 2} +!6 = distinct !DISubprogram(name: "test_redundant_load", scope: !1, file: !1, line: 2, type: !7, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2) +!7 = !DISubroutineType(types: !2) +!8 = !DILocation(line: 3, scope: !6) +!9 = !DILocation(line: 5, scope: !6) +!10 = !DILocation(line: 6, scope: !6) +!11 = !DILocation(line: 7, scope: !6) +!12 = !DILocation(line: 8, scope: !6) +!13 = !DILocation(line: 10, scope: !6)