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

This PR adds the support for the SV_Target semantic and improved the
diagnostics when the stage is correct, but the direction is disallowed.

Author: Keenuts

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13213,6 +13213,8 @@ 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 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

@@ -134,9 +134,6 @@ class SemaHLSL : public SemaBase {
   void CheckEntryPoint(FunctionDecl *FD);
   bool CheckResourceBinOp(BinaryOperatorKind Opc, Expr *LHSExpr, Expr *RHSExpr,
                           SourceLocation Loc);
-  void DiagnoseAttrStageMismatch(
-      const Attr *A, llvm::Triple::EnvironmentType Stage,
-      std::initializer_list<llvm::Triple::EnvironmentType> AllowedStages);
 
   QualType handleVectorBinOpConversion(ExprResult &LHS, ExprResult &RHS,
                                        QualType LHSType, QualType RHSType,
@@ -244,6 +241,17 @@ class SemaHLSL : public SemaBase {
     std::optional<uint32_t> Index;
   };
 
+  enum IOType {
+    In = 0b01,
+    Out = 0b10,
+    InOut = 0b11,
+  };
+
+  struct SemanticStageInfo {
+    llvm::Triple::EnvironmentType Stage;
+    IOType Direction;
+  };
+
 private:
   void collectResourceBindingsOnVarDecl(VarDecl *D);
   void collectResourceBindingsOnUserRecordDecl(const VarDecl *VD,
@@ -269,6 +277,14 @@ class SemaHLSL : public SemaBase {
 
   void diagnoseAvailabilityViolations(TranslationUnitDecl *TU);
 
+  void diagnoseAttrStageMismatch(
+      const Attr *A, llvm::Triple::EnvironmentType Stage,
+      std::initializer_list<llvm::Triple::EnvironmentType> AllowedStages);
+
+  void diagnoseSemanticStageMismatch(
+      const Attr *A, llvm::Triple::EnvironmentType Stage, bool IsInput,
+      std::initializer_list<SemanticStageInfo> AllowedStages);
+
   uint32_t getNextImplicitBindingOrderID() {
     return ImplicitBindingNextOrderID++;
   }

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -774,6 +774,8 @@ void CGHLSLRuntime::emitSystemSemanticStore(IRBuilder<> &B, llvm::Value *Source,
       createSPIRVBuiltinStore(B, CGM.getModule(), Source,
                               Semantic->getAttrName()->getName(),
                               /* BuiltIn::Position */ 0);
+  } else if (SemanticName == "SV_TARGET") {
+    emitUserSemanticStore(B, Source, Decl, Semantic, Index);
   } else
     llvm_unreachable("non-handled system semantic. FIXME.");
 }

clang/lib/Sema/SemaHLSL.cpp

@@ -873,14 +873,14 @@ void SemaHLSL::CheckEntryPoint(FunctionDecl *FD) {
   case llvm::Triple::Miss:
   case llvm::Triple::Callable:
     if (const auto *NT = FD->getAttr<HLSLNumThreadsAttr>()) {
-      DiagnoseAttrStageMismatch(NT, ST,
+      diagnoseAttrStageMismatch(NT, ST,
                                 {llvm::Triple::Compute,
                                  llvm::Triple::Amplification,
                                  llvm::Triple::Mesh});
       FD->setInvalidDecl();
     }
     if (const auto *WS = FD->getAttr<HLSLWaveSizeAttr>()) {
-      DiagnoseAttrStageMismatch(WS, ST,
+      diagnoseAttrStageMismatch(WS, ST,
                                 {llvm::Triple::Compute,
                                  llvm::Triple::Amplification,
                                  llvm::Triple::Mesh});
@@ -954,7 +954,8 @@ void SemaHLSL::checkSemanticAnnotation(
       SemanticName == "SV_GROUPID") {
 
     if (ST != llvm::Triple::Compute)
-      DiagnoseAttrStageMismatch(SemanticAttr, ST, {llvm::Triple::Compute});
+      diagnoseSemanticStageMismatch(SemanticAttr, ST, IsInput,
+                                    {{llvm::Triple::Compute, IOType::In}});
 
     if (SemanticAttr->getSemanticIndex() != 0) {
       std::string PrettyName =
@@ -967,14 +968,15 @@ void SemaHLSL::checkSemanticAnnotation(
   }
 
   if (SemanticName == "SV_POSITION") {
-    // SV_Position can is I/O for vertex shaders.
-    // For pixel shaders, only valid as input.
-    // Note: for SPIR-V, not backed by a builtin when used as input in a vertex
-    // shaders.
-    if (ST == llvm::Triple::Vertex || (ST == llvm::Triple::Pixel && IsInput))
-      return;
-    DiagnoseAttrStageMismatch(SemanticAttr, ST,
-                              {llvm::Triple::Pixel, llvm::Triple::Vertex});
+    diagnoseSemanticStageMismatch(SemanticAttr, ST, IsInput,
+                                  {{llvm::Triple::Vertex, IOType::InOut},
+                                   {llvm::Triple::Pixel, IOType::In}});
+    return;
+  }
+
+  if (SemanticName == "SV_TARGET") {
+    diagnoseSemanticStageMismatch(SemanticAttr, ST, IsInput,
+                                  {{llvm::Triple::Pixel, IOType::Out}});
     return;
   }
 
@@ -984,7 +986,7 @@ void SemaHLSL::checkSemanticAnnotation(
     llvm_unreachable("Unknown SemanticAttr");
 }
 
-void SemaHLSL::DiagnoseAttrStageMismatch(
+void SemaHLSL::diagnoseAttrStageMismatch(
     const Attr *A, llvm::Triple::EnvironmentType Stage,
     std::initializer_list<llvm::Triple::EnvironmentType> AllowedStages) {
   SmallVector<StringRef, 8> StageStrings;
@@ -998,6 +1000,37 @@ void SemaHLSL::DiagnoseAttrStageMismatch(
       << (AllowedStages.size() != 1) << join(StageStrings, ", ");
 }
 
+void SemaHLSL::diagnoseSemanticStageMismatch(
+    const Attr *A, llvm::Triple::EnvironmentType Stage, bool IsInput,
+    std::initializer_list<SemanticStageInfo> Allowed) {
+
+  for (auto &Case : Allowed) {
+    if (Case.Stage != Stage)
+      continue;
+
+    if (IsInput && Case.Direction & IOType::In)
+      return;
+    if (!IsInput && Case.Direction & IOType::Out)
+      return;
+
+    Diag(A->getLoc(), diag::err_hlsl_semantic_unsupported_direction_for_stage)
+        << A->getAttrName() << (IsInput ? "input" : "output")
+        << llvm::Triple::getEnvironmentTypeName(Case.Stage);
+    return;
+  }
+
+  SmallVector<StringRef, 8> StageStrings;
+  llvm::transform(
+      Allowed, std::back_inserter(StageStrings), [](SemanticStageInfo Case) {
+        return StringRef(
+            HLSLShaderAttr::ConvertEnvironmentTypeToStr(Case.Stage));
+      });
+
+  Diag(A->getLoc(), diag::err_hlsl_attr_unsupported_in_stage)
+      << A->getAttrName() << llvm::Triple::getEnvironmentTypeName(Stage)
+      << (Allowed.size() != 1) << join(StageStrings, ", ");
+}
+
 template <CastKind Kind>
 static void castVector(Sema &S, ExprResult &E, QualType &Ty, unsigned Sz) {
   if (const auto *VTy = Ty->getAs<VectorType>())
@@ -1799,6 +1832,16 @@ void SemaHLSL::diagnoseSystemSemanticAttr(Decl *D, const ParsedAttr &AL,
     return;
   }
 
+  if (SemanticName == "SV_TARGET") {
+    const auto *VT = ValueType->getAs<VectorType>();
+    if (!ValueType->hasFloatingRepresentation() ||
+        (VT && VT->getNumElements() > 4))
+      Diag(AL.getLoc(), diag::err_hlsl_attr_invalid_type)
+          << AL << "float/float1/float2/float3/float4";
+    D->addAttr(createSemanticAttr<HLSLParsedSemanticAttr>(AL, Index));
+    return;
+  }
+
   Diag(AL.getLoc(), diag::err_hlsl_unknown_semantic) << AL;
 }
 

clang/test/CodeGenHLSL/semantics/SV_Target.ps.hlsl

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-pixel -x hlsl -emit-llvm -finclude-default-header -disable-llvm-passes -o - %s | FileCheck %s --check-prefix=CHECK-SPIRV
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-pixel -x hlsl -emit-llvm -finclude-default-header -disable-llvm-passes -o - %s | FileCheck %s --check-prefix=CHECK-DXIL
+
+// CHECK-SPIRV: @SV_Target0 = external hidden thread_local addrspace(8) global <4 x float>, !spirv.Decorations ![[#MD_2:]]
+
+// CHECK: define void @main() {{.*}} {
+float4 main(float4 p : SV_Position) : SV_Target {
+  // CHECK-SPIRV: %[[#R:]] = call spir_func <4 x float> @_Z4mainDv4_f(<4 x float> %[[#]])
+  // CHECK-SPIRV:            store <4 x float> %[[#R]], ptr addrspace(8) @SV_Target0, align 16
+
+  // CHECK-DXIL:    %[[#TMP:]] = call <4 x float> @_Z4mainDv4_f(<4 x float> %SV_Position0)
+  // CHECK-DXIL:                 call void @llvm.dx.store.output.v4f32(i32 4, i32 0, i32 0, i8 0, i32 poison, <4 x float> %[[#TMP]])
+  return p;
+}
+
+// CHECK-SPIRV-DAG: ![[#MD_2]] = !{![[#MD_3:]]}
+// CHECK-SPIRV-DAG: ![[#MD_3]] = !{i32 30, i32 0}
+//                                      |       `-> Location index
+//                                      `-> SPIR-V decoration 'Location'

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 {{attribute 'SV_Position' is unsupported in 'pixel' shaders, requires one of the following: pixel, vertex}}
+// expected-error@-1 {{semantic 'SV_Position' is unsupported as output for stage pixel}}
   return a;
 }

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

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-pixel -finclude-default-header -x hlsl -verify -o - %s
+// 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}}
+  return a;
+}

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

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-vertex -finclude-default-header -x hlsl -verify -o - %s
+// RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-vertex -finclude-default-header -x hlsl -verify -o - %s
+
+float4 main(float4 a : SV_Target) : A {
+// expected-error@-1 {{attribute 'SV_Target' is unsupported in 'vertex' shaders, requires pixel}}
+  return a;
+}
+

clang/test/SemaHLSL/Semantics/target.vs.output.hlsl

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-vertex -finclude-default-header -x hlsl -verify -o - %s
+// RUN: %clang_cc1 -triple spirv-pc-vulkan1.3-vertex -finclude-default-header -x hlsl -verify -o - %s
+
+float4 main(float4 a : SV_Position) : SV_Target {
+// expected-error@-1 {{attribute 'SV_Target' is unsupported in 'vertex' shaders, requires pixel}}
+  return a;
+}

llvm/test/CodeGen/SPIRV/semantics/target.ps.ll

@@ -0,0 +1,33 @@
+; RUN: llc -O0 -verify-machineinstrs -mtriple=spirv-vulkan-unknown %s -o - | FileCheck %s
+; RUN: %if spirv-tools %{ llc -O0 -mtriple=spirv-vulkan-unknown %s -o - -filetype=obj | spirv-val %}
+
+; CHECK-DAG:        OpDecorate %[[#INPUT:]] BuiltIn FragCoord
+; CHECK-DAG:        OpDecorate %[[#OUTPUT:]] Location 0
+
+; CHECK-DAG:   %[[#float:]] = OpTypeFloat 32
+; CHECK-DAG:      %[[#v4:]] = OpTypeVector %[[#float]] 4
+; CHECK-DAG:   %[[#ptr_i:]] = OpTypePointer Input %[[#v4]]
+; CHECK-DAG:   %[[#ptr_o:]] = OpTypePointer Output %[[#v4]]
+
+; CHECK-DAG:      %[[#INPUT]] = OpVariable %[[#ptr_i]] Input
+; CHECK-DAG:      %[[#OUTPUT]] = OpVariable %[[#ptr_o]] Output
+
+@SV_Position = external hidden thread_local addrspace(7) externally_initialized constant <4 x float>, !spirv.Decorations !0
+@SV_Target0 = external hidden thread_local addrspace(8) global <4 x float>, !spirv.Decorations !2
+
+define void @main() #1 {
+entry:
+  %0 = load <4 x float>, ptr addrspace(7) @SV_Position, align 16
+  store <4 x float> %0, ptr addrspace(8) @SV_Target0, align 16
+  ret void
+
+; CHECK: %[[#TMP:]] = OpLoad %[[#v4]] %[[#INPUT]] Aligned 16
+; CHECK:              OpStore %[[#OUTPUT]] %[[#TMP]] Aligned 16
+}
+
+!0 = !{!1}
+!1 = !{i32 11, i32 15}
+!2 = !{!3}
+!3 = !{i32 30, i32 0}
+
+