Implement the `EvaluateAttributeCentroid` HLSL Function

[farzonl]

• Implement EvaluateAttributeCentroid clang builtin,
• Link EvaluateAttributeCentroid clang builtin with hlsl_intrinsics.h
• Add sema checks for EvaluateAttributeCentroid to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for EvaluateAttributeCentroid to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/EvaluateAttributeCentroid.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/EvaluateAttributeCentroid-errors.hlsl
• Create the int_dx_EvaluateAttributeCentroid intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_EvaluateAttributeCentroid to 89 in DXIL.td
• Create the EvaluateAttributeCentroid.ll and EvaluateAttributeCentroid_errors.ll tests in llvm/test/CodeGen/DirectX/

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
89	EvalCentroid	6.0	('pixel',)

SPIR-V

There is no support for EvaluateAttributeCentroid when targeting SPIR-V.

Test Case(s)

Example 1

//dxc EvaluateAttributeCentroid_test.hlsl -T lib_6_8 -enable-16bit-types -O0

[numthreads(1, 1, 1)]
[shader("pixel")]
float4 fn(float4 p1 : COLOR ) : SV_Target {

	return EvaluateAttributeCentroid(p1);
}

HLSL:

Evaluates at the pixel centroid.

Syntax

numeric EvaluateAttributeCentroid(
  in attrib numeric value
);

Parameters

value [in]

Type: attrib numeric

The input value.

Remarks

Interpolation mode can be linear or linear_no_perspective on the variable. Use of centroid or sample is ignored. Attributes with constant interpolation are also allowed, in which case the sample index is ignored.

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 5 and higher shader models	yes

 

This function is supported in the following types of shaders:

Vertex	Hull	Domain	Geometry	Pixel	Compute
				x

 

See also

Intrinsic Functions

Shader Model 5