Implement the CallShader HLSL Function

[farzonl]

• Implement CallShader clang builtin,
• Link CallShader clang builtin with hlsl_intrinsics.h
• Add sema checks for CallShader to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for CallShader to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/CallShader.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/CallShader-errors.hlsl
• Create the int_dx_CallShader intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_CallShader to 159 in DXIL.td
• Create the CallShader.ll and CallShader_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_CallShader intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the CallShader lowering and map it to int_spv_CallShader in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/CallShader.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
159	CallShader	6.3	('library', 'closesthit', 'raygeneration', 'miss', 'callable')

SPIR-V

OpExecuteCallableKHR:

Description:

Reserved.

Capability:
RayTracingKHR

Reserved.

Word Count	Opcode	Results	Operands
3	4446	<id> SBT Index	<id> Callable Data

Test Case(s)

Example 1

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

struct RayPayload
{
	float4 color;
	float distance;
};
export void fn(uint p1, RayPayload p2) {
    return CallShader(p1, p2);
}

HLSL:

Invokes another shader from within a shader.

Syntax

This intrinsic function definition is equivalent to the following function template:

template<param_t>
void CallShader(uint ShaderIndex, inout param_t Parameter);

Parameters

ShaderIndex

An unsigned integer representing the index into the callable shader table specified in the call to DispatchRays.

Parameter

The user-defined parameters to pass to the callable shader. This parameter structure must match the parameter structure used in the callable shader pointed to in the shader table.

Return Value

void

Remarks

This function can be called from the following raytracing shader types:

• Callable shader
• Closest hit shader
• Miss shader
• Ray generation shader

See also

• Direct3D 12 raytracing HLSL reference