[HLSL][DXIL] Implement refract intrinsic

clang/include/clang/Basic/BuiltinsSPIRVVK.td

@@ -11,3 +11,4 @@ include "clang/Basic/BuiltinsSPIRVBase.td"
 
 def reflect : SPIRVBuiltin<"void(...)", [NoThrow, Const]>;
 def faceforward : SPIRVBuiltin<"void(...)", [NoThrow, Const, CustomTypeChecking]>;
+def refract : SPIRVBuiltin<"void(...)", [NoThrow, Const, CustomTypeChecking]>;

clang/lib/CodeGen/TargetBuiltins/SPIR.cpp

@@ -58,6 +58,21 @@ Value *CodeGenFunction::EmitSPIRVBuiltinExpr(unsigned BuiltinID,
         /*ReturnType=*/I->getType(), Intrinsic::spv_reflect,
         ArrayRef<Value *>{I, N}, nullptr, "spv.reflect");
   }
+  case SPIRV::BI__builtin_spirv_refract: {
+    Value *I = EmitScalarExpr(E->getArg(0));
+    Value *N = EmitScalarExpr(E->getArg(1));
+    Value *eta = EmitScalarExpr(E->getArg(2));
+    assert(E->getArg(0)->getType()->hasFloatingRepresentation() &&
+           E->getArg(1)->getType()->hasFloatingRepresentation() &&
+           E->getArg(2)->getType()->isFloatingType() &&
+           "refract operands must have a float representation");
+    assert(E->getArg(0)->getType()->isVectorType() &&
+           E->getArg(1)->getType()->isVectorType() &&
+           "refract I and N operands must be a vector");
+    return Builder.CreateIntrinsic(
+        /*ReturnType=*/I->getType(), Intrinsic::spv_refract,
+        ArrayRef<Value *>{I, N, eta}, nullptr, "spv.refract");
+  }
   case SPIRV::BI__builtin_spirv_smoothstep: {
     Value *Min = EmitScalarExpr(E->getArg(0));
     Value *Max = EmitScalarExpr(E->getArg(1));

clang/lib/Headers/hlsl/hlsl_detail.h

@@ -45,6 +45,14 @@ template <typename T> struct is_arithmetic {
   static const bool Value = __is_arithmetic(T);
 };
 
+template <typename T> struct is_vector {
+  static const bool value = false;
+};
+
+template <typename T, int N> struct is_vector<vector<T, N>> {
+  static const bool value = true;
+};
+
 template <typename T, int N>
 using HLSL_FIXED_VECTOR =
     vector<__detail::enable_if_t<(N > 1 && N <= 4), T>, N>;

clang/lib/Headers/hlsl/hlsl_intrinsic_helpers.h

@@ -71,6 +71,17 @@ constexpr vector<T, L> reflect_vec_impl(vector<T, L> I, vector<T, L> N) {
 #endif
 }
 
+template <typename T, typename U> constexpr T refract_impl(T I, T N, U Eta) {
+#if (__has_builtin(__builtin_spirv_refract))
+  if (is_vector<T>::value)
+    return __builtin_spirv_refract(I, N, Eta);
+#endif
+  T Mul = dot(N, I);
+  T K = 1 - Eta * Eta * (1 - Mul * Mul);
+  T Result = (Eta * I - (Eta * Mul + sqrt(K)) * N);
+  return select<T>(K < 0, static_cast<T>(0), Result);
+}
+
 template <typename T> constexpr T fmod_impl(T X, T Y) {
 #if !defined(__DIRECTX__)
   return __builtin_elementwise_fmod(X, Y);

clang/lib/Headers/hlsl/hlsl_intrinsics.h

@@ -475,6 +475,65 @@ reflect(__detail::HLSL_FIXED_VECTOR<float, L> I,
   return __detail::reflect_vec_impl(I, N);
 }
 
+//===----------------------------------------------------------------------===//
+// refract builtin
+//===----------------------------------------------------------------------===//
+
+/// \fn T refract(T I, T N, T eta)
+/// \brief Returns a refraction using an entering ray, \a I, a surface
+/// normal, \a N and refraction index \a eta
+/// \param I The entering ray.
+/// \param N The surface normal.
+/// \param eta The refraction index.
+///
+/// The return value is a floating-point vector that represents the refraction
+/// using the refraction index, \a eta, for the direction of the entering ray,
+/// \a I, off a surface with the normal \a N.
+///
+/// This function calculates the refraction vector using the following formulas:
+/// k = 1.0 - eta * eta * (1.0 - dot(N, I) * dot(N, I))
+/// if k < 0.0 the result is 0.0
+/// otherwise, the result is eta * I - (eta * dot(N, I) + sqrt(k)) * N
+///
+/// I and N must already be normalized in order to achieve the desired result.
+///
+/// I and N must be a scalar or vector whose component type is
+/// floating-point.
+///
+/// eta must be a 16-bit or 32-bit floating-point scalar.
+///
+/// Result type, the type of I, and the type of N must all be the same type.
+
+template <typename T>
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+const inline __detail::enable_if_t<__detail::is_arithmetic<T>::Value &&
+                                       __detail::is_same<half, T>::value,
+                                   T> refract(T I, T N, T eta) {
+  return __detail::refract_impl(I, N, eta);
+}
+
+template <typename T>
+const inline __detail::enable_if_t<
+    __detail::is_arithmetic<T>::Value && __detail::is_same<float, T>::value, T>
+refract(T I, T N, T eta) {
+  return __detail::refract_impl(I, N, eta);
+}
+
+template <int L>
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+const inline __detail::HLSL_FIXED_VECTOR<half, L> refract(
+    __detail::HLSL_FIXED_VECTOR<half, L> I,
+    __detail::HLSL_FIXED_VECTOR<half, L> N, half eta) {
+  return __detail::refract_impl(I, N, eta);
+}
+
+template <int L>
+const inline __detail::HLSL_FIXED_VECTOR<float, L>
+refract(__detail::HLSL_FIXED_VECTOR<float, L> I,
+        __detail::HLSL_FIXED_VECTOR<float, L> N, float eta) {
+  return __detail::refract_impl(I, N, eta);
+}
+
 //===----------------------------------------------------------------------===//
 // smoothstep builtin
 //===----------------------------------------------------------------------===//

clang/lib/Sema/SemaHLSL.cpp

@@ -3995,4 +3995,4 @@ bool SemaHLSL::handleInitialization(VarDecl *VDecl, Expr *&Init) {
   }
   Init = C;
   return true;
-}
+}

clang/lib/Sema/SemaSPIRV.cpp

@@ -46,6 +46,59 @@ static bool CheckAllArgsHaveSameType(Sema *S, CallExpr *TheCall) {
   return false;
 }
 
+static bool CheckAllArgTypesAreCorrect(
+    Sema *S, CallExpr *TheCall,
+    llvm::ArrayRef<
+        llvm::function_ref<bool(Sema *, SourceLocation, int, QualType)>>
+        Checks) {
+  unsigned NumArgs = TheCall->getNumArgs();
+  assert(Checks.size() == NumArgs &&
+         "Wrong number of checks for Number of args.");
+  // Apply each check to the corresponding argument
+  for (unsigned I = 0; I < NumArgs; ++I) {
+    Expr *Arg = TheCall->getArg(I);
+    if (Checks[I](S, Arg->getBeginLoc(), I + 1, Arg->getType()))
+      return true;
+  }
+  return false;
+}
+
+static bool CheckAllArgTypesAreCorrect(
+    Sema *S, CallExpr *TheCall,
+    llvm::function_ref<bool(Sema *, SourceLocation, int, QualType)> Check) {
+  return CheckAllArgTypesAreCorrect(
+      S, TheCall,
+      SmallVector<
+          llvm::function_ref<bool(Sema *, SourceLocation, int, QualType)>, 4>(
+          TheCall->getNumArgs(), Check));
+}
+
+static bool CheckFloatOrHalfRepresentation(Sema *S, SourceLocation Loc,
+                                           int ArgOrdinal,
+                                           clang::QualType PassedType) {
+  clang::QualType BaseType =
+      PassedType->isVectorType()
+          ? PassedType->castAs<clang::VectorType>()->getElementType()
+          : PassedType;
+  if (!BaseType->isHalfType() && !BaseType->isFloat32Type())
+    return S->Diag(Loc, diag::err_builtin_invalid_arg_type)
+           << ArgOrdinal << /* scalar or vector of */ 5 << /* no int */ 0
+           << /* half or float */ 2 << PassedType;
+  return false;
+}
+
+static bool CheckFloatOrHalfScalarRepresentation(Sema *S, SourceLocation Loc,
+                                                 int ArgOrdinal,
+                                                 clang::QualType PassedType) {
+  const auto *VecTy = PassedType->getAs<VectorType>();
+
+  if (VecTy || (!PassedType->isHalfType() && !PassedType->isFloat32Type()))
+    return S->Diag(Loc, diag::err_builtin_invalid_arg_type)
+           << ArgOrdinal << /* scalar */ 1 << /* no int */ 0
+           << /* half or float */ 2 << PassedType;
+  return false;
+}
+
 static std::optional<int>
 processConstant32BitIntArgument(Sema &SemaRef, CallExpr *Call, int Argument) {
   ExprResult Arg =
@@ -235,6 +288,30 @@ bool SemaSPIRV::CheckSPIRVBuiltinFunctionCall(const TargetInfo &TI,
     TheCall->setType(RetTy);
     break;
   }
+  case SPIRV::BI__builtin_spirv_refract: {
+    if (SemaRef.checkArgCount(TheCall, 3))
+      return true;
+
+    llvm::function_ref<bool(Sema *, SourceLocation, int, QualType)>
+        ChecksArr[] = {CheckFloatOrHalfRepresentation,
+                       CheckFloatOrHalfRepresentation,
+                       CheckFloatOrHalfScalarRepresentation};
+    if (CheckAllArgTypesAreCorrect(&SemaRef, TheCall,
+                                   llvm::ArrayRef(ChecksArr)))
+      return true;
+
+    ExprResult C = TheCall->getArg(2);
+    QualType ArgTyC = C.get()->getType();
+    if (!ArgTyC->isFloatingType()) {
+      SemaRef.Diag(C.get()->getBeginLoc(), diag::err_builtin_invalid_arg_type)
+          << 3 << /* scalar*/ 5 << /* no int */ 0 << /* fp */ 1 << ArgTyC;
+      return true;
+    }
+
+    QualType RetTy = TheCall->getArg(0)->getType();
+    TheCall->setType(RetTy);
+    break;
+  }
   case SPIRV::BI__builtin_spirv_smoothstep: {
     if (SemaRef.checkArgCount(TheCall, 3))
       return true;