[PATCH] D145317: [ValueMapper] Preserve poison types during value mapping

[Carl Ritson via Phabricator via llvm-commits]

critson created this revision.
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Poison needs to be treated directly during type remap otherwise
it will be considered an instance of undef.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145317

Files:
  llvm/lib/Transforms/Utils/ValueMapper.cpp
  llvm/unittests/Transforms/Utils/ValueMapperTest.cpp


Index: llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
===================================================================
--- llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
+++ llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
@@ -397,4 +397,28 @@
   EXPECT_EQ(MDC, ValueMapper(VM).mapValue(*MDA));
 }
 
+// Type remapper which remaps all types to same destination.
+class TestTypeRemapper : public ValueMapTypeRemapper {
+public:
+  TestTypeRemapper(Type *Ty) : DstTy(Ty) { }
+  Type *remapType(Type *srcTy) { return DstTy; }
+private:
+  Type *DstTy;
+};
+
+TEST(ValueMapperTest, mapValuePoisonWithTypeRemap) {
+  LLVMContext C;
+  Type *OldTy = Type::getInt8Ty(C);
+  Type *NewTy = Type::getInt32Ty(C);
+
+  TestTypeRemapper TM(NewTy);
+  ValueToValueMapTy VM;
+  ValueMapper Mapper(VM, RF_None, &TM);
+
+  // Check that poison is still poison and has not been converted to undef.
+  auto *OldPoison = PoisonValue::get(OldTy);
+  auto *NewPoison = PoisonValue::get(NewTy);
+  EXPECT_EQ(NewPoison, Mapper.mapValue(*OldPoison));
+}
+
 } // end namespace
Index: llvm/lib/Transforms/Utils/ValueMapper.cpp
===================================================================
--- llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -523,6 +523,8 @@
   if (isa<ConstantVector>(C))
     return getVM()[V] = ConstantVector::get(Ops);
   // If this is a no-operand constant, it must be because the type was remapped.
+  if (isa<PoisonValue>(C))
+    return getVM()[V] = PoisonValue::get(NewTy);
   if (isa<UndefValue>(C))
     return getVM()[V] = UndefValue::get(NewTy);
   if (isa<ConstantAggregateZero>(C))


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