[IR] Disallow ZeroInit for spirv.Image (#73887)

According to spirv spec, OpConstantNull's result type can't be image
type. So we can't generate zeroinitializer for spirv.Image.

Author: wenju-he

llvm/lib/IR/Type.cpp

@@ -834,6 +834,8 @@ struct TargetTypeInfo {
 static TargetTypeInfo getTargetTypeInfo(const TargetExtType *Ty) {
   LLVMContext &C = Ty->getContext();
   StringRef Name = Ty->getName();
+  if (Name.equals("spirv.Image"))
+    return TargetTypeInfo(PointerType::get(C, 0), TargetExtType::CanBeGlobal);
   if (Name.starts_with("spirv."))
     return TargetTypeInfo(PointerType::get(C, 0), TargetExtType::HasZeroInit,
                           TargetExtType::CanBeGlobal);

llvm/unittests/Transforms/Utils/ValueMapperTest.cpp

@@ -423,7 +423,7 @@ TEST(ValueMapperTest, mapValuePoisonWithTypeRemap) {
 
 TEST(ValueMapperTest, mapValueConstantTargetNoneToLayoutTypeNullValue) {
   LLVMContext C;
-  auto *OldTy = TargetExtType::get(C, "spirv.Image");
+  auto *OldTy = TargetExtType::get(C, "spirv.Event");
   Type *NewTy = OldTy->getLayoutType();
 
   TestTypeRemapper TM(NewTy);