[HLSL][SPIR-V] Add support for SV_Target semantic

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13231,8 +13231,9 @@ def err_hlsl_semantic_indexing_not_supported
 def err_hlsl_init_priority_unsupported : Error<
   "initializer priorities are not supported in HLSL">;
 def err_hlsl_semantic_index_overlap : Error<"semantic index overlap %0">;
-def err_hlsl_semantic_unsupported_direction_for_stage
-    : Error<"semantic %0 is unsupported as %1 for stage %2">;
+def err_hlsl_semantic_unsupported_iotype_for_stage
+    : Error<"semantic %0 is unsupported in %2 shaders as %1, requires one of "
+            "the following: %3">;
 
 def warn_hlsl_user_defined_type_missing_member: Warning<"binding type '%select{t|u|b|s|c}0' only applies to types containing %select{SRV resources|UAV resources|constant buffer resources|sampler state|numeric types}0">, InGroup<LegacyConstantRegisterBinding>;
 def err_hlsl_binding_type_mismatch: Error<"binding type '%select{t|u|b|s|c}0' only applies to %select{SRV resources|UAV resources|constant buffer resources|sampler state|numeric variables in the global scope}0">;

clang/include/clang/Sema/SemaHLSL.h

@@ -249,7 +249,7 @@ class SemaHLSL : public SemaBase {
 
   struct SemanticStageInfo {
     llvm::Triple::EnvironmentType Stage;
-    IOType Direction;
+    IOType AllowedIOTypesMask;
   };
 
 private:

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -783,8 +783,10 @@ void CGHLSLRuntime::emitSystemSemanticStore(IRBuilder<> &B, llvm::Value *Source,
     }
   }
 
-  if (SemanticName == "SV_TARGET")
+  if (SemanticName == "SV_TARGET") {
     emitUserSemanticStore(B, Source, Decl, Semantic, Index);
+    return;
+  }
 
   llvm_unreachable(
       "Store hasn't been implemented yet for this system semantic. FIXME");

clang/lib/Sema/SemaHLSL.cpp

@@ -1010,14 +1010,26 @@ void SemaHLSL::diagnoseSemanticStageMismatch(
     if (Case.Stage != Stage)
       continue;
 
-    if (IsInput && Case.Direction & IOType::In)
+    if (IsInput && Case.AllowedIOTypesMask & IOType::In)
       return;
-    if (!IsInput && Case.Direction & IOType::Out)
+    if (!IsInput && Case.AllowedIOTypesMask & IOType::Out)
       return;
 
-    Diag(A->getLoc(), diag::err_hlsl_semantic_unsupported_direction_for_stage)
+    SmallVector<std::string, 8> ValidCases;
+    llvm::transform(
+        Allowed, std::back_inserter(ValidCases), [](SemanticStageInfo Case) {
+          std::string Type =
+              Case.AllowedIOTypesMask == IOType::InOut
+                  ? " inout"
+                  : (Case.AllowedIOTypesMask & IOType::In ? " in" : " out");
+          return std::string(
+                     HLSLShaderAttr::ConvertEnvironmentTypeToStr(Case.Stage)) +
+                 Type;
+        });
+    Diag(A->getLoc(), diag::err_hlsl_semantic_unsupported_iotype_for_stage)
         << A->getAttrName() << (IsInput ? "input" : "output")
-        << llvm::Triple::getEnvironmentTypeName(Case.Stage);
+        << llvm::Triple::getEnvironmentTypeName(Case.Stage)
+        << join(ValidCases, ", ");
     return;
   }
 

clang/test/SemaHLSL/Semantics/position.ps.hlsl

@@ -2,6 +2,6 @@
 // RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-pixel -finclude-default-header -x hlsl -verify -o - %s
 
 float4 main(float4 a : A) : SV_Position {
-// expected-error@-1 {{semantic 'SV_Position' is unsupported as output for stage pixel}}
+// expected-error@-1 {{semantic 'SV_Position' is unsupported in pixel shaders as output, requires one of the following: vertex inout, pixel in}}
   return a;
 }

clang/test/SemaHLSL/Semantics/target.ps.input.hlsl

@@ -2,6 +2,6 @@
 // RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-pixel -finclude-default-header -x hlsl -verify -o - %s
 
 float4 main(float4 a : SV_Target) : A {
-// expected-error@-1 {{semantic 'SV_Target' is unsupported as input for stage pixel}}
+// expected-error@-1 {{semantic 'SV_Target' is unsupported in pixel shaders as input, requires one of the following: pixel out}}
   return a;
 }