Implement the HitKind HLSL Function

[farzonl]

• Implement HitKind clang builtin,
• Link HitKind clang builtin with hlsl_intrinsics.h
• Add sema checks for HitKind to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for HitKind to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/HitKind.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/HitKind-errors.hlsl
• Create the int_dx_HitKind intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_HitKind to 143 in DXIL.td
• Create the HitKind.ll and HitKind_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_HitKind intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the HitKind lowering and map it to int_spv_HitKind in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/HitKind.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
143	HitKind	6.3	('library', 'intersection', 'anyhit', 'closesthit')

SPIR-V

HitKindKHR

Short Description

HitKindKHR - Kind of hit that triggered an any-hit or closest hit ray
shader

Description

HitKindKHR
A variable decorated with the HitKindKHR decoration will describe
the intersection that triggered the execution of the current shader. The
values are determined by the intersection shader. For user-defined
intersection shaders this is the value that was passed to the “Hit Kind”
operand of OpReportIntersectionKHR . For triangle intersection
candidates, this will be one of HitKindFrontFacingTriangleKHR or
HitKindBackFacingTriangleKHR .

Valid Usage

• 
  VUID-HitKindKHR-HitKindKHR-04242
  The HitKindKHR decoration must be used only within the
  AnyHitKHR or ClosestHitKHR Execution Model

• 
  VUID-HitKindKHR-HitKindKHR-04243
  The variable decorated with HitKindKHR must be declared using
  the Input Storage Class

• 
  VUID-HitKindKHR-HitKindKHR-04244
  The variable decorated with HitKindKHR must be declared as a
  scalar 32-bit integer value

Test Case(s)

Example 1

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

export uint fn() {
    return HitKind();
}

SPIRV Example(s):

Example 2

//dxc HitKind_spirv_test.hlsl -T lib_6_8 -E fn -enable-16bit-types -spirv -fspv-target-env=universal1.5 -fcgl -O0

[shader("intersection")]
void fn() {
uint 	ret = HitKind();
}

HLSL:

Returns the value passed as the HitKind parameter to ReportHit.

Syntax

uint HitKind();

Remarks

If the intersection was reported by fixed-function triangle intersection, HitKind will be one of HIT_KIND_TRIANGLE_FRONT_FACE (254) or HIT_KIND_TRIANGLE_BACK_FACE (255).

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

• Any Hit Shader
• Closest Hit Shader
• Intersection Shader

See also

Direct3D 12 Raytracing HLSL Reference