[HLSL] Implement the lit intrinsic

clang/lib/Headers/hlsl/hlsl_intrinsic_helpers.h

@@ -109,6 +109,18 @@ constexpr vector<T, N> smoothstep_vec_impl(vector<T, N> Min, vector<T, N> Max,
 #endif
 }
 
+template <typename T> constexpr vector<T, 4> lit_impl(T NDotL, T NDotH, T M) {
+  bool DiffuseCond = NDotL < 0;
+  T Diffuse = select<T>(DiffuseCond, 0, NDotL);
+  vector<T, 4> Result = {1, Diffuse, 0, 1};
+  // clang-format off
+  bool SpecularCond = or(DiffuseCond, (NDotH < 0));
+  // clang-format on
+  T SpecularExp = exp(log(NDotH) * M);
+  Result[2] = select<T>(SpecularCond, 0, SpecularExp);
+  return Result;
+}
+
 } // namespace __detail
 } // namespace hlsl
 

clang/lib/Headers/hlsl/hlsl_intrinsics.h

@@ -268,6 +268,30 @@ const inline float length(__detail::HLSL_FIXED_VECTOR<float, N> X) {
   return __detail::length_vec_impl(X);
 }
 
+//===----------------------------------------------------------------------===//
+// lit builtins
+//===----------------------------------------------------------------------===//
+
+/// \fn vector<T, 4> lit(T NDotL, T NDotH, T M)
+/// \brief Returns a lighting coefficient vector.
+/// \param NDotL The dot product of the normalized surface normal and the
+/// light vector.
+/// \param NDotH The dot product of the half-angle vector and the surface
+/// normal.
+/// \param M A specular exponent.
+///
+/// This function returns a lighting coefficient vector (ambient, diffuse,
+/// specular, 1).
+
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+const inline half4 lit(half NDotL, half NDotH, half M) {
+  return __detail::lit_impl(NDotL, NDotH, M);
+}
+
+const inline float4 lit(float NDotL, float NDotH, float M) {
+  return __detail::lit_impl(NDotL, NDotH, M);
+}
+
 //===----------------------------------------------------------------------===//
 // D3DCOLORtoUBYTE4 builtin
 //===----------------------------------------------------------------------===//

clang/test/CodeGenHLSL/builtins/lit.hlsl

@@ -0,0 +1,34 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple dxil-pc-shadermodel6.3-library %s -fnative-half-type -emit-llvm -O1 -o - | FileCheck %s
+
+// CHECK-LABEL: test_lit_half
+// CHECK-SAME: half noundef nofpclass(nan inf) [[NDOTL:%.*]], half noundef nofpclass(nan inf) [[NDOTH:%.*]], half noundef nofpclass(nan inf) [[M:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[CMP_I:%.*]] = fcmp reassoc nnan ninf nsz arcp afn olt half [[NDOTL]], 0xH0000
+// CHECK-NEXT:    [[HLSL_SELECT_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn half @llvm.maxnum.f16(half [[NDOTL]], half 0xH0000)
+// CHECK-NEXT:    [[VECINIT2_I:%.*]] = insertelement <4 x half> <half 0xH3C00, half poison, half poison, half 0xH3C00>, half [[HLSL_SELECT_I]], i64 1
+// CHECK-NEXT:    [[CMP4_I:%.*]] = fcmp reassoc nnan ninf nsz arcp afn olt half [[NDOTH]], 0xH0000
+// CHECK-NEXT:    [[HLSL_OR_I:%.*]] = or i1 [[CMP_I]], [[CMP4_I]]
+// CHECK-NEXT:    [[ELT_LOG_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn half @llvm.log.f16(half [[NDOTH]])
+// CHECK-NEXT:    [[MUL_I:%.*]] = fmul reassoc nnan ninf nsz arcp afn half [[ELT_LOG_I]], [[M]]
+// CHECK-NEXT:    [[ELT_EXP_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn half @llvm.exp.f16(half [[MUL_I]])
+// CHECK-NEXT:    [[HLSL_SELECT7_I:%.*]] = select reassoc nnan ninf nsz arcp afn i1 [[HLSL_OR_I]], half 0xH0000, half [[ELT_EXP_I]]
+// CHECK-NEXT:    [[VECINS_I:%.*]] = insertelement <4 x half> [[VECINIT2_I]], half [[HLSL_SELECT7_I]], i64 2
+// CHECK-NEXT:    ret <4 x half> [[VECINS_I]]
+half4 test_lit_half(half NDotL, half NDotH, half M) { return lit(NDotL, NDotH, M); }
+
+// CHECK-LABEL: test_lit_float
+// CHECK-SAME: float noundef nofpclass(nan inf) [[NDOTL:%.*]], float noundef nofpclass(nan inf) [[NDOTH:%.*]], float noundef nofpclass(nan inf) [[M:%.*]]) local_unnamed_addr #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[CMP_I:%.*]] = fcmp reassoc nnan ninf nsz arcp afn olt float [[NDOTL]], 0.000000e+00
+// CHECK-NEXT:    [[HLSL_SELECT_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn float @llvm.maxnum.f32(float [[NDOTL]], float 0.000000e+00)
+// CHECK-NEXT:    [[VECINIT2_I:%.*]] = insertelement <4 x float> <float 1.000000e+00, float poison, float poison, float 1.000000e+00>, float [[HLSL_SELECT_I]], i64 1
+// CHECK-NEXT:    [[CMP4_I:%.*]] = fcmp reassoc nnan ninf nsz arcp afn olt float [[NDOTH]], 0.000000e+00
+// CHECK-NEXT:    [[HLSL_OR_I:%.*]] = or i1 [[CMP_I]], [[CMP4_I]]
+// CHECK-NEXT:    [[ELT_LOG_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn float @llvm.log.f32(float [[NDOTH]])
+// CHECK-NEXT:    [[MUL_I:%.*]] = fmul reassoc nnan ninf nsz arcp afn float [[ELT_LOG_I]], [[M]]
+// CHECK-NEXT:    [[ELT_EXP_I:%.*]] = tail call reassoc nnan ninf nsz arcp afn float @llvm.exp.f32(float [[MUL_I]])
+// CHECK-NEXT:    [[HLSL_SELECT7_I:%.*]] = select reassoc nnan ninf nsz arcp afn i1 [[HLSL_OR_I]], float 0.000000e+00, float [[ELT_EXP_I]]
+// CHECK-NEXT:    [[VECINS_I:%.*]] = insertelement <4 x float> [[VECINIT2_I]], float [[HLSL_SELECT7_I]], i64 2
+// CHECK-NEXT:    ret <4 x float> [[VECINS_I]]
+float4 test_lit_float(float NDotL, float NDotH, float M) { return lit(NDotL, NDotH, M); }

clang/test/SemaHLSL/BuiltIns/lit-errors.hlsl

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only -disable-llvm-passes -verify -verify-ignore-unexpected=note
+
+float4 test_double_inputs(double p0, double p1, double p2) {
+  return lit(p0, p1, p2);
+  // expected-error@-1 {{call to 'lit' is ambiguous}}
+}
+
+float4 test_int_inputs(int p0, int p1, int p2) {
+  return lit(p0, p1, p2);
+  // expected-error@-1 {{call to 'lit' is ambiguous}}
+}
+
+float4 test_bool_inputs(bool p0, bool p1, bool p2) {
+  return lit(p0, p1, p2);
+  // expected-error@-1 {{call to 'lit' is ambiguous}}
+}