[llvm] r355301 - [InstCombine] Mark debug values as unavailable after DCE.

[Davide Italiano via llvm-commits]

Author: davide
Date: Sun Mar  3 20:38:58 2019
New Revision: 355301

URL: http://llvm.org/viewvc/llvm-project?rev=355301&view=rev
Log:
[InstCombine] Mark debug values as unavailable after DCE.

Fixes PR40838.

Added:
    llvm/trunk/test/Transforms/InstCombine/unavailable-debug.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=355301&r1=355300&r2=355301&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Sun Mar  3 20:38:58 2019
@@ -3323,7 +3323,8 @@ static bool AddReachableCodeToWorklist(B
       if (isInstructionTriviallyDead(Inst, TLI)) {
         ++NumDeadInst;
         LLVM_DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
-        salvageDebugInfo(*Inst);
+        if (!salvageDebugInfo(*Inst))
+          replaceDbgUsesWithUndef(Inst);
         Inst->eraseFromParent();
         MadeIRChange = true;
         continue;

Added: llvm/trunk/test/Transforms/InstCombine/unavailable-debug.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/unavailable-debug.ll?rev=355301&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/unavailable-debug.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/unavailable-debug.ll Sun Mar  3 20:38:58 2019
@@ -0,0 +1,81 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Make sure to update the debug value after dead code elimination.
+; CHECK: %call = call signext i8 @b(i32 6), !dbg !39
+; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 undef, metadata !30, metadata !DIExpression()), !dbg !38
+
+ at e = common local_unnamed_addr global i8 0, align 1, !dbg !0
+ at c = common local_unnamed_addr global i32 0, align 4, !dbg !6
+ at d = common local_unnamed_addr global i32 0, align 4, !dbg !10
+
+define signext i8 @b(i32 %f) local_unnamed_addr #0 !dbg !18 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %f, metadata !22, metadata !DIExpression()), !dbg !23
+  %conv = trunc i32 %f to i8, !dbg !24
+  ret i8 %conv, !dbg !25
+}
+
+define i32 @main() local_unnamed_addr #0 !dbg !26 {
+entry:
+  %0 = load i8, i8* @e, align 1, !dbg !31, !tbaa !32
+  %conv = sext i8 %0 to i32, !dbg !31
+  store i32 %conv, i32* @c, align 4, !dbg !35, !tbaa !36
+  call void @llvm.dbg.value(metadata i32 -1372423381, metadata !30, metadata !DIExpression()), !dbg !38
+  %call = call signext i8 @b(i32 6), !dbg !39
+  %conv1 = sext i8 %call to i32, !dbg !39
+  call void @llvm.dbg.value(metadata i32 %conv1, metadata !30, metadata !DIExpression()), !dbg !38
+  %1 = load i32, i32* @d, align 4, !dbg !40, !tbaa !36
+  %call2 = call i32 (...) @optimize_me_not(), !dbg !41
+  ret i32 0, !dbg !42
+}
+
+declare i32 @optimize_me_not(...) local_unnamed_addr #1
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!13, !14, !15, !16}
+!llvm.ident = !{!17}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "e", scope: !2, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 9.0.0 (https://github.com/llvm/llvm-project b306ef12f046353ea5bda4b3b77759e57909a0db)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: GNU)
+!3 = !DIFile(filename: "a.c", directory: "/Users/davide/llvm/build/bin")
+!4 = !{}
+!5 = !{!6, !10, !0}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "c", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!8 = !DIDerivedType(tag: DW_TAG_typedef, name: "a", file: !3, line: 1, baseType: !9)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !DIGlobalVariableExpression(var: !11, expr: !DIExpression())
+!11 = distinct !DIGlobalVariable(name: "d", scope: !2, file: !3, line: 2, type: !8, isLocal: false, isDefinition: true)
+!12 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!13 = !{i32 2, !"Dwarf Version", i32 4}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = !{i32 1, !"wchar_size", i32 4}
+!16 = !{i32 7, !"PIC Level", i32 2}
+!17 = !{!"clang version 9.0.0 (https://github.com/llvm/llvm-project b306ef12f046353ea5bda4b3b77759e57909a0db)"}
+!18 = distinct !DISubprogram(name: "b", scope: !3, file: !3, line: 4, type: !19, scopeLine: 4, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !21)
+!19 = !DISubroutineType(types: !20)
+!20 = !{!12, !9}
+!21 = !{!22}
+!22 = !DILocalVariable(name: "f", arg: 1, scope: !18, file: !3, line: 4, type: !9)
+!23 = !DILocation(line: 4, column: 9, scope: !18)
+!24 = !DILocation(line: 4, column: 21, scope: !18)
+!25 = !DILocation(line: 4, column: 14, scope: !18)
+!26 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 5, type: !27, scopeLine: 5, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !29)
+!27 = !DISubroutineType(types: !28)
+!28 = !{!9}
+!29 = !{!30}
+!30 = !DILocalVariable(name: "l_1499", scope: !26, file: !3, line: 7, type: !8)
+!31 = !DILocation(line: 6, column: 7, scope: !26)
+!32 = !{!33, !33, i64 0}
+!33 = !{!"omnipotent char", !34, i64 0}
+!34 = !{!"Simple C/C++ TBAA"}
+!35 = !DILocation(line: 6, column: 5, scope: !26)
+!36 = !{!37, !37, i64 0}
+!37 = !{!"int", !33, i64 0}
+!38 = !DILocation(line: 7, column: 5, scope: !26)
+!39 = !DILocation(line: 8, column: 12, scope: !26)
+!40 = !DILocation(line: 9, column: 11, scope: !26)
+!41 = !DILocation(line: 10, column: 3, scope: !26)
+!42 = !DILocation(line: 11, column: 1, scope: !26)