[PATCH] D16169: [Utils] Fix incorrect dbg.declare store conversion

[Keno Fischer via llvm-commits]

loladiro created this revision.
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The dbg.declare -> dbg.value conversion did not check which operand of the store instruction the alloca was passed to. As a result code that stored the address of an alloca, rather than storing to the alloca, would still trigger the conversion routine, leading to the insertion of an incorrect dbg.value intrinsic.

Repository:
  rL LLVM

http://reviews.llvm.org/D16169

Files:
  lib/Transforms/Utils/Local.cpp
  test/Transforms/Util/store-first-op.ll

Index: test/Transforms/Util/store-first-op.ll
===================================================================
--- /dev/null
+++ test/Transforms/Util/store-first-op.ll
@@ -0,0 +1,36 @@
+; RUN: opt -instcombine -S %s | FileCheck %s
+
+%foo = type { i8 }
+
+; Function Attrs: nounwind uwtable
+define void @_ZN4llvm13ScaledNumbers10multiply64Emm() {
+entry:
+  %getU = alloca %foo, align 1
+; This is supposed to make sure that the declare conversion, does not accidentally think the store OF
+; %getU is a store TO %getU. There are valid reasons to have an llvm.dbg.value here, but if the pass
+; pass is changed to emit such, a more specific check should be added to make sure that the llvm.dbg.value
+; is correct.
+; CHECK-NOT: @llvm.dbg.value(metadata %foo* %getU
+  call void @llvm.dbg.declare(metadata %foo* %getU, metadata !3, metadata !6), !dbg !7
+  store %foo* %getU, %foo** undef, align 8, !tbaa !8
+  unreachable
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (https://github.com/llvm-mirror/clang 89dda3855cda574f355e6defa1d77bdae5053994) (llvm/trunk 257597)", isOptimized: true, runtimeVersion: 0, emissionKind: 1)
+!1 = !DIFile(filename: "none", directory: ".")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !DILocalVariable(name: "getU", scope: !4, file: !1, line: 25, type: !5)
+!4 = distinct !DISubprogram(name: "multiply64", linkageName: "_ZN4llvm13ScaledNumbers10multiply64Emm", scope: null, file: !1, line: 22, isLocal: false, isDefinition: true, scopeLine: 23, flags: DIFlagPrototyped, isOptimized: true)
+!5 = !DICompositeType(tag: DW_TAG_class_type, scope: !4, file: !1, line: 25, size: 8, align: 8)
+!6 = !DIExpression()
+!7 = !DILocation(line: 25, column: 8, scope: !4)
+!8 = !{!9, !9, i64 0}
+!9 = !{i64 0}
Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -1133,10 +1133,12 @@
     // the stack slot (and at a lexical-scope granularity). Later
     // passes will attempt to elide the stack slot.
     if (AI && !isArray(AI)) {
-      for (User *U : AI->users())
-        if (StoreInst *SI = dyn_cast<StoreInst>(U))
-          ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
-        else if (LoadInst *LI = dyn_cast<LoadInst>(U))
+      for (auto &AIUse : AI->uses()) {
+        User *U = AIUse.getUser();
+        if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+          if (AIUse.getOperandNo() == 1)
+            ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+        } else if (LoadInst *LI = dyn_cast<LoadInst>(U))
           ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
         else if (CallInst *CI = dyn_cast<CallInst>(U)) {
           // This is a call by-value or some other instruction that
@@ -1150,6 +1152,7 @@
                                       DIB.createExpression(NewDIExpr),
                                       DDI->getDebugLoc(), CI);
         }
+      }
       DDI->eraseFromParent();
     }
   }


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