[spirv] Relax SV_Position type requirements (#4275)

A valid vertex shader output variable with SV_Position semantics may be
constructed from any HLSL BuiltinType that translates to a 32-bit
floating point type in the SPIR-V backend, so relax the requirements to
allow the use of additonal types (such as half4) when
-enable-16bit-types is false.

Fixes #4262

tools/clang/lib/SPIRV/DeclResultIdMapper.cpp

@@ -517,9 +517,27 @@ bool insertSeenSemanticsForEntryPointIfNotExist(
   return true;
 }
 
-// Returns whether the type is float4 or a composite type recursively including
-// only float4 e.g., float4, float4[1], struct S { float4 foo[1]; }.
-bool containOnlyVecWithFourFloats(QualType type) {
+// Returns whether the type is translated to a 32-bit floating point type,
+// depending on whether SPIR-V codegen options are configured to use 16-bit
+// types when possible.
+bool is32BitFloatingPointType(BuiltinType::Kind kind, bool use16Bit) {
+  // Always translated into 32-bit floating point types.
+  if (kind == BuiltinType::Float || kind == BuiltinType::LitFloat)
+    return true;
+
+  // Translated into 32-bit floating point types when run without
+  // -enable-16bit-types.
+  if (kind == BuiltinType::Half || kind == BuiltinType::HalfFloat ||
+      kind == BuiltinType::Min10Float || kind == BuiltinType::Min16Float)
+    return !use16Bit;
+
+  return false;
+}
+
+// Returns whether the type is a 4-component 32-bit float or a composite type
+// recursively including only such a vector e.g., float4, float4[1], struct S {
+// float4 foo[1]; }.
+bool containOnlyVecWithFourFloats(QualType type, bool use16Bit) {
   if (type->isReferenceType())
     type = type->getPointeeType();
 
@@ -532,7 +550,7 @@ bool containOnlyVecWithFourFloats(QualType type) {
         (const ConstantArrayType *)type->getAsArrayTypeUnsafe();
     elemCount = hlsl::GetArraySize(type);
     return elemCount == 1 &&
-           containOnlyVecWithFourFloats(arrayType->getElementType());
+           containOnlyVecWithFourFloats(arrayType->getElementType(), use16Bit);
   }
 
   if (const auto *structType = type->getAs<RecordType>()) {
@@ -540,7 +558,7 @@ bool containOnlyVecWithFourFloats(QualType type) {
     for (const auto *field : structType->getDecl()->fields()) {
       if (fieldCount != 0)
         return false;
-      if (!containOnlyVecWithFourFloats(field->getType()))
+      if (!containOnlyVecWithFourFloats(field->getType(), use16Bit))
         return false;
       ++fieldCount;
     }
@@ -550,7 +568,8 @@ bool containOnlyVecWithFourFloats(QualType type) {
   QualType elemType = {};
   if (isVectorType(type, &elemType, &elemCount)) {
     if (const auto *builtinType = elemType->getAs<BuiltinType>()) {
-      return elemCount == 4 && builtinType->getKind() == BuiltinType::Float;
+      return elemCount == 4 &&
+             is32BitFloatingPointType(builtinType->getKind(), use16Bit);
     }
     return false;
   }
@@ -3300,9 +3319,10 @@ SpirvVariable *DeclResultIdMapper::createSpirvStageVar(
   // by VSOut, HS/DS/GS In/Out, MSOut.
   case hlsl::Semantic::Kind::Position: {
     if (sigPointKind == hlsl::SigPoint::Kind::VSOut &&
-        !containOnlyVecWithFourFloats(type)) {
-      emitError("semantic Position must be float4 or a composite type "
-                "recursively including only float4",
+        !containOnlyVecWithFourFloats(
+            type, theEmitter.getSpirvOptions().enable16BitTypes)) {
+      emitError("SV_Position must be a 4-component 32-bit float vector or a "
+                "composite which recursively contains only such a vector",
                 srcLoc);
     }
 

tools/clang/unittests/SPIRV/CodeGenSpirvTest.cpp

@@ -2929,9 +2929,11 @@ float4 PSMain(PSInput input) : SV_TARGET
 
 std::string getVertexPositionTypeTestShader(const std::string &subType,
                                             const std::string &positionType,
-                                            const std::string &check) {
-  const std::string command(R"(// RUN: %dxc -T vs_6_0 -E main)");
-  const std::string code = command + subType + R"(
+                                            const std::string &check,
+                                            bool use16bit) {
+  const std::string code = std::string(R"(// RUN: %dxc -T vs_6_2 -E main)") +
+                           (use16bit ? R"( -enable-16bit-types)" : R"()") + R"(
+)" + subType + R"(
 struct output {
 )" + positionType + R"(
 };
@@ -2946,33 +2948,37 @@ output main() : SV_Position
 }
 
 const char *kInvalidPositionTypeForVSErrorMessage =
-    "// CHECK: error: semantic Position must be float4 or a composite type "
-    "recursively including only float4";
+    "// CHECK: error: SV_Position must be a 4-component 32-bit float vector or "
+    "a composite which recursively contains only such a vector";
 
 TEST_F(FileTest, PositionInVSWithArrayType) {
-  runCodeTest(getVertexPositionTypeTestShader(
-                  "", "float x[4];", kInvalidPositionTypeForVSErrorMessage),
-              Expect::Failure);
+  runCodeTest(
+      getVertexPositionTypeTestShader(
+          "", "float x[4];", kInvalidPositionTypeForVSErrorMessage, false),
+      Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithDoubleType) {
-  runCodeTest(getVertexPositionTypeTestShader(
-                  "", "double4 x;", kInvalidPositionTypeForVSErrorMessage),
-              Expect::Failure);
+  runCodeTest(
+      getVertexPositionTypeTestShader(
+          "", "double4 x;", kInvalidPositionTypeForVSErrorMessage, false),
+      Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithIntType) {
   runCodeTest(getVertexPositionTypeTestShader(
-                  "", "int4 x;", kInvalidPositionTypeForVSErrorMessage),
+                  "", "int4 x;", kInvalidPositionTypeForVSErrorMessage, false),
               Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithMatrixType) {
-  runCodeTest(getVertexPositionTypeTestShader(
-                  "", "float1x4 x;", kInvalidPositionTypeForVSErrorMessage),
-              Expect::Failure);
+  runCodeTest(
+      getVertexPositionTypeTestShader(
+          "", "float1x4 x;", kInvalidPositionTypeForVSErrorMessage, false),
+      Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithInvalidFloatVectorType) {
-  runCodeTest(getVertexPositionTypeTestShader(
-                  "", "float3 x;", kInvalidPositionTypeForVSErrorMessage),
-              Expect::Failure);
+  runCodeTest(
+      getVertexPositionTypeTestShader(
+          "", "float3 x;", kInvalidPositionTypeForVSErrorMessage, false),
+      Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithInvalidInnerStructType) {
   runCodeTest(getVertexPositionTypeTestShader(
@@ -2980,7 +2986,8 @@ TEST_F(FileTest, PositionInVSWithInvalidInnerStructType) {
 struct InvalidType {
   float3 x;
 };)",
-                  "InvalidType x;", kInvalidPositionTypeForVSErrorMessage),
+                  "InvalidType x;", kInvalidPositionTypeForVSErrorMessage,
+                  false),
               Expect::Failure);
 }
 TEST_F(FileTest, PositionInVSWithValidInnerStructType) {
@@ -2991,7 +2998,43 @@ struct validType {
                                               "validType x;", R"(
 // CHECK: %validType = OpTypeStruct %v4float
 // CHECK:    %output = OpTypeStruct %validType
-)"));
+)",
+                                              false));
+}
+TEST_F(FileTest, PositionInVSWithValidFloatType) {
+  runCodeTest(getVertexPositionTypeTestShader("", "float4 x;", R"(
+// CHECK:    %output = OpTypeStruct %v4float
+)",
+                                              false));
+}
+TEST_F(FileTest, PositionInVSWithValidMin10Float4Type) {
+  runCodeTest(getVertexPositionTypeTestShader("", "min10float4 x;", R"(
+// CHECK:    %output = OpTypeStruct %v4float
+)",
+                                              false));
+}
+TEST_F(FileTest, PositionInVSWithValidMin16Float4Type) {
+  runCodeTest(getVertexPositionTypeTestShader("", "min16float4 x;", R"(
+// CHECK:    %output = OpTypeStruct %v4float
+)",
+                                              false));
+}
+TEST_F(FileTest, PositionInVSWithValidHalf4Type) {
+  runCodeTest(getVertexPositionTypeTestShader("", "half4 x;", R"(
+// CHECK:    %output = OpTypeStruct %v4float
+)",
+                                              false));
+}
+TEST_F(FileTest, PositionInVSWithInvalidHalf4Type) {
+  runCodeTest(getVertexPositionTypeTestShader(
+                  "", "half4 x;", kInvalidPositionTypeForVSErrorMessage, true),
+              Expect::Failure);
+}
+TEST_F(FileTest, PositionInVSWithInvalidMin10Float4Type) {
+  runCodeTest(
+      getVertexPositionTypeTestShader(
+          "", "min10float4 x;", kInvalidPositionTypeForVSErrorMessage, true),
+      Expect::Failure);
 }
 TEST_F(FileTest, ShaderDebugInfoFunction) {
   runFileTest("shader.debug.function.hlsl");