Add semantic clarification to error on missing output semantic (#4562)

* test that when output of entry point function is missing semantic, the output is specified in the error message

* remove old comment

* add alternate error output message among the set of expected errors

lib/HLSL/HLSignatureLower.cpp

@@ -270,9 +270,12 @@ void HLSignatureLower::ProcessArgument(Function *func,
 
   llvm::StringRef semanticStr = paramAnnotation.GetSemanticString();
   if (semanticStr.empty()) {
-    dxilutil::EmitErrorOnFunction(HLM.GetModule()->getContext(), func,
-        "Semantic must be defined for all parameters of an entry function or "
-        "patch constant function");
+    
+    std::string msg = "Semantic must be defined for all ";
+    msg += (qual == DxilParamInputQual::Out) ? "outputs " : "parameters ";
+    msg += "of an entry function or patch constant function";
+    
+    dxilutil::EmitErrorOnFunction(HLM.GetModule()->getContext(), func, msg);
     return;
   }
   UpdateSemanticAndInterpMode(semanticStr, interpMode, sigPoint->GetKind(),

tools/clang/test/HLSLFileCheck/hlsl/semantics/legacy/semantic_missing.hlsl

@@ -0,0 +1,8 @@
+// RUN: %dxc /Tps_6_0 %s | FileCheck %s 
+// CHECK: error: Semantic must be defined for all outputs of an entry function or patch constant function
+
+[RootSignature("")]
+float main(float a : A, uint b : SV_Coverage)
+{
+    return a;
+}

tools/clang/unittests/HLSL/SystemValueTest.cpp

@@ -535,11 +535,13 @@ TEST_F(SystemValueTest, VerifyMissingSemanticFailure) {
       // TODO: add tests for mesh/amplification shaders to system-values.hlsl
       continue;
     }
+
     std::wstring sigDefValue(L"Def_Arb_NoSem(uint, arb0)");
     CComPtr<IDxcOperationResult> pResult;
     CompileHLSLTemplate(pResult, sp, sigDefValue);
     const char *Errors[] = {
       "error: Semantic must be defined for all parameters of an entry function or patch constant function",
+      "error: Semantic must be defined for all outputs of an entry function or patch constant function"
     };
     CheckAnyOperationResultMsg(pResult, Errors, _countof(Errors));
   }