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Implement the ddy HLSL Function #99099

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@farzonl

Description

@farzonl
  • Implement ddy clang builtin,
  • Link ddy clang builtin with hlsl_intrinsics.h
  • Add sema checks for ddy to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
  • Add codegen for ddy to EmitHLSLBuiltinExpr in CGBuiltin.cpp
  • Add codegen tests to clang/test/CodeGenHLSL/builtins/ddy.hlsl
  • Add sema tests to clang/test/SemaHLSL/BuiltIns/ddy-errors.hlsl
  • Create the int_dx_ddy intrinsic in IntrinsicsDirectX.td
  • Create the DXILOpMapping of int_dx_ddy to 84 in DXIL.td
  • Create the ddy.ll and ddy_errors.ll tests in llvm/test/CodeGen/DirectX/
  • Create the int_spv_ddy intrinsic in IntrinsicsSPIRV.td
  • In SPIRVInstructionSelector.cpp create the ddy lowering and map it to int_spv_ddy in SPIRVInstructionSelector::selectIntrinsic.
  • Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/ddy.ll

DirectX

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

SPIR-V

OpDPdy:

Description:

Same result as either OpDPdyFine or
OpDPdyCoarse on P. Selection of which one is
based on external factors.

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:
Shader

Word Count Opcode Results Operands

4

208

<id>
Result Type

Result <id>

<id>
P

Test Case(s)

Example 1

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

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

HLSL:

Returns the partial derivative of the specified value with respect to the screen-space y-coordinate.

ret ddy(x)

This function computes the partial derivative with respect to the screen-space y-coordinate. To compute the partial derivative with respect to the screen-space x-coordinate, use the ddx function.

This function is only supported in pixel shaders.

Parameters

Item Description
x
[in] The specified value.

Return Value

The partial derivative of the x parameter.

Type Description

Name Template Type Component Type Size
x scalar, vector, or matrix float any
ret same as input x float same dimension(s) as input x

Minimum Shader Model

This function is supported in the following shader models.

Shader Model Supported
Shader Model 5 and higher shader models yes
Shader Model 4 yes
Shader Model 3 (DirectX HLSL) yes
Shader Model 2 (DirectX HLSL) yes in ps_2_x; unsupported in ps_2_0.
Shader Model 1 (DirectX HLSL) no

This function is supported in the following types of shaders:

Vertex Hull Domain Geometry Pixel Compute
x

See also

Intrinsic Functions (DirectX HLSL)

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