Implement the `ddx_coarse` HLSL Function

[farzonl]

• Implement ddx_coarse clang builtin,
• Link ddx_coarse clang builtin with hlsl_intrinsics.h
• Add sema checks for ddx_coarse to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for ddx_coarse to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/ddx_coarse.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/ddx_coarse-errors.hlsl
• Create the int_dx_ddx_coarse intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_ddx_coarse to 83 in DXIL.td
• Create the ddx_coarse.ll and ddx_coarse_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_ddx_coarse intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the ddx_coarse lowering and map it to int_spv_ddx_coarse in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/ddx_coarse.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
83	DerivCoarseX	6.0	('library', 'pixel', 'compute', 'amplification', 'mesh', 'node')

SPIR-V

OpDPdxCoarse:

Description:

Result is the partial derivative of P with respect to the window x
coordinate. Uses local differencing based on the value of P for the
current fragment’s neighbors, and possibly, but not necessarily,
includes the value of P for the current fragment. That is, over a
given area, the implementation can compute x derivatives in fewer
unique locations than would be allowed for
OpDPdxFine.

Result Type must be a scalar or vector of floating-point
type using the IEEE 754 encoding. The component width must
be 32 bits.

The type of P must be the same as Result Type. P is the value to
take the derivative of.

This instruction is only valid in the Fragment Execution
Model.

Capability:
DerivativeControl

Word Count	Opcode	Results	Operands
4	213	<id> Result Type	Result <id>	<id> P

Test Case(s)

Example 1

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

export float4 fn(float4 p1) {
    return ddx_coarse(p1);
}

HLSL:

Computes a low precision partial derivative with respect to the screen-space x-coordinate.

Syntax

float ddx_coarse(
  in float value
);

Parameters

value [in]

Type: float

The input value.

Return value

Type: float

The low precision partial derivative of value.

Remarks

The following overloaded versions are also available:

float2 ddx_coarse(float2 value);
float3 ddx_coarse(float3 value);
float4 ddx_coarse(float4 value);

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

[damyanp]

We should consider when implementing this microsoft/DirectXShaderCompiler#5744