[HLSL] Add trunc library function

[bob80905]

dont just paste the clang format commit onto the revision

[bob80905]

The commit still isn't included, adding ^ character

[python3kgae]

The PR title is acos but trunc is added.

[python3kgae]

LGTM.
Remember to double check the commit message updated to trunc too.

Just noticed we don't have double trunc(double) for hlsl now (hlsl 2021). Need make sure to generate float overload DXIL on older shader model when parameter is double in hlsl.

clang/lib/Headers/hlsl/hlsl_intrinsics.h

 sin(double);
 __attribute__((clang_builtin_alias(__builtin_elementwise_sin)))
 double2 sin(double2);
 __attribute__((clang_builtin_alias(__builtin_elementwise_sin)))
 double3 sin(double3);
 __attribute__((clang_builtin_alias(__builtin_elementwise_sin)))
 double4 sin(double4);
 
+// trunc builtins
+#ifdef __HLSL_ENABLE_16_BIT
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+half trunc(half);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+half2 trunc(half2);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+half3 trunc(half3);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+half4 trunc(half4);
+#endif
+
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc))) float
+trunc(float);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+float2 trunc(float2);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+float3 trunc(float3);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+float4 trunc(float4);
+
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc))) double
+trunc(double);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+double2 trunc(double2);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+double3 trunc(double3);
+__attribute__((clang_builtin_alias(__builtin_elementwise_trunc)))
+double4 trunc(double4);
+
 } // namespace hlsl
 #endif //_HLSL_HLSL_INTRINSICS_H_

clang/test/CodeGenHLSL/builtins/trunc.hlsl

+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -fnative-half-type \
+// RUN:   -emit-llvm -disable-llvm-passes -O3 -o - | FileCheck %s
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -emit-llvm -disable-llvm-passes \
+// RUN:   -D__HLSL_ENABLE_16_BIT -o - | FileCheck %s --check-prefix=NO_HALF
+
+// CHECK: define noundef half @
+// CHECK: call half @llvm.trunc.f16(
+// NO_HALF: define noundef float @"?test_trunc_half@@YA$halff@$halff@@Z"(
+// NO_HALF: call float @llvm.trunc.f32(
+half test_trunc_half ( half p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <2 x half> @
+// CHECK: call <2 x half> @llvm.trunc.v2f16
+// NO_HALF: define noundef <2 x float> @"?test_trunc_float2@@YAT?$__vector@M$01@__clang@@T12@@Z"(
+// NO_HALF: call <2 x float> @llvm.trunc.v2f32(
+half2 test_trunc_half2 ( half2 p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <3 x half> @
+// CHECK: call <3 x half> @llvm.trunc.v3f16
+// NO_HALF: define noundef <3 x float> @"?test_trunc_float3@@YAT?$__vector@M$02@__clang@@T12@@Z"(
+// NO_HALF: call <3 x float> @llvm.trunc.v3f32(
+half3 test_trunc_half3 ( half3 p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <4 x half> @
+// CHECK: call <4 x half> @llvm.trunc.v4f16
+// NO_HALF: define noundef <4 x float> @"?test_trunc_float4@@YAT?$__vector@M$03@__clang@@T12@@Z"(
+// NO_HALF: call <4 x float> @llvm.trunc.v4f32(
+half4 test_trunc_half4 ( half4 p0 ) {
+  return trunc ( p0 );
+}
+
+// CHECK: define noundef float @
+// CHECK: call float @llvm.trunc.f32(
+float test_trunc_float ( float p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <2 x float> @
+// CHECK: call <2 x float> @llvm.trunc.v2f32
+float2 test_trunc_float2 ( float2 p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <3 x float> @
+// CHECK: call <3 x float> @llvm.trunc.v3f32
+float3 test_trunc_float3 ( float3 p0 ) {
+  return trunc ( p0 );
+}
+// CHECK: define noundef <4 x float> @
+// CHECK: call <4 x float> @llvm.trunc.v4f32
+float4 test_trunc_float4 ( float4 p0 ) {
+  return trunc ( p0 );
+}