remove undef usage

Author: Keenuts

clang/lib/CodeGen/CodeGenModule.cpp

@@ -5638,8 +5638,6 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
     Init = llvm::UndefValue::get(getTypes().ConvertTypeForMem(ASTTy));
   else if (D->hasAttr<LoaderUninitializedAttr>())
     Init = llvm::UndefValue::get(getTypes().ConvertTypeForMem(ASTTy));
-  else if (GetGlobalVarAddressSpace(D) == LangAS::hlsl_input)
-    Init = llvm::UndefValue::get(getTypes().ConvertTypeForMem(ASTTy));
   else if (!InitExpr) {
     // This is a tentative definition; tentative definitions are
     // implicitly initialized with { 0 }.
@@ -5763,15 +5761,16 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
       getCUDARuntime().internalizeDeviceSideVar(D, Linkage);
     }
     getCUDARuntime().handleVarRegistration(D, *GV);
-  } else if (LangOpts.HLSL &&
-             GetGlobalVarAddressSpace(D) == LangAS::hlsl_input) {
+  }
+
+  if (LangOpts.HLSL && GetGlobalVarAddressSpace(D) == LangAS::hlsl_input) {
     // HLSL Input variables are considered to be set by the driver/pipeline, but
     // only visible to a single thread/wave.
     GV->setExternallyInitialized(true);
+  } else {
+    GV->setInitializer(Init);
   }
 
-  GV->setInitializer(Init);
-
   if (LangOpts.HLSL)
     getHLSLRuntime().handleGlobalVarDefinition(D, GV);
 

clang/test/CodeGenHLSL/vk-input-builtin.hlsl

@@ -3,7 +3,7 @@
 
 [[vk::ext_builtin_input(/* WorkgroupId */ 26)]]
 static const uint3 groupid;
-// CHECK: @_ZL7groupid = local_unnamed_addr addrspace(7) externally_initialized constant <3 x i32> undef, align 16, !spirv.Decorations [[META0:![0-9]+]]
+// CHECK: @_ZL7groupid = external local_unnamed_addr addrspace(7) externally_initialized constant <3 x i32>, align 16, !spirv.Decorations [[META0:![0-9]+]]
 
 RWStructuredBuffer<int> output : register(u1, space0);
 

llvm/test/CodeGen/SPIRV/hlsl-intrinsics/vk-ext-builtin-input.ll

@@ -11,7 +11,7 @@
 ; CHECK-DAG:   %[[#ptr_Input_uint:]] = OpTypePointer Input %[[#uint]]
 ; CHECK-DAG: %[[#ptr_Input_v3uint:]] = OpTypePointer Input %[[#v3uint]]
 ; CHECK-DAG:      %[[#WorkgroupId:]] = OpVariable %[[#ptr_Input_v3uint]] Input
-@var = local_unnamed_addr addrspace(7) externally_initialized constant <3 x i32> undef, align 16, !spirv.Decorations !0
+@var = external local_unnamed_addr addrspace(7) externally_initialized constant <3 x i32>, align 16, !spirv.Decorations !0
 
 define i32 @foo() {
 entry: