Implement the `DispatchRaysDimensions` HLSL Function

[farzonl]

• Implement DispatchRaysDimensions clang builtin,
• Link DispatchRaysDimensions clang builtin with hlsl_intrinsics.h
• Add sema checks for DispatchRaysDimensions to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for DispatchRaysDimensions to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/DispatchRaysDimensions.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/DispatchRaysDimensions-errors.hlsl
• Create the int_dx_DispatchRaysDimensions intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_DispatchRaysDimensions to 146 in DXIL.td
• Create the DispatchRaysDimensions.ll and DispatchRaysDimensions_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_DispatchRaysDimensions intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the DispatchRaysDimensions lowering and map it to int_spv_DispatchRaysDimensions in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/DispatchRaysDimensions.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
146	DispatchRaysDimensions	6.3	('library', 'raygeneration', 'intersection', 'anyhit', 'closesthit', 'miss', 'callable')

SPIR-V

LaunchSizeKHR

Short Description

LaunchSizeKHR - Launch dimensions for ray shaders

Description

LaunchSizeKHR
A variable decorated with the LaunchSizeKHR decoration will contain
the width , height , and depth dimensions passed to the
vkCmdTraceRaysKHR command that initiated this
shader execution. The width is in the first component, the
height is in the second component, and the depth is in the third
component.

Valid Usage

• 
  VUID-LaunchSizeKHR-LaunchSizeKHR-04269
  The LaunchSizeKHR decoration must be used only within the
  RayGenerationKHR , IntersectionKHR , AnyHitKHR ,
  ClosestHitKHR , MissKHR , or CallableKHR Execution
Model

• 
  VUID-LaunchSizeKHR-LaunchSizeKHR-04270
  The variable decorated with LaunchSizeKHR must be declared
  using the Input Storage Class

• 
  VUID-LaunchSizeKHR-LaunchSizeKHR-04271
  The variable decorated with LaunchSizeKHR must be declared as
  a three-component vector of 32-bit integer values

Test Case(s)

Example 1

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

export uint3 fn() {
    return DispatchRaysDimensions();
}

SPIRV Example(s):

Example 2

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

[shader("intersection")]
void fn() {
uint3 	ret = DispatchRaysDimensions();
}

HLSL:

The width, height and depth values from the D3D12_DISPATCH_RAYS_DESC structure specified in the originating DispatchRays call.

Syntax

uint3 DispatchRaysDimensions();

Remarks

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

• Any Hit Shader
• Callable Shader
• Closest Hit Shader
• Intersection Shader
• Miss Shader
• Ray Generation Shader

See also

• Direct3D 12 Raytracing HLSL Reference