Implement the `IsHelperLane` HLSL Function

[farzonl]

• Implement IsHelperLane clang builtin,
• Link IsHelperLane clang builtin with hlsl_intrinsics.h
• Add sema checks for IsHelperLane to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for IsHelperLane to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/IsHelperLane.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/IsHelperLane-errors.hlsl
• Create the int_dx_IsHelperLane intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_IsHelperLane to 221 in DXIL.td
• Create the IsHelperLane.ll and IsHelperLane_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_IsHelperLane intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the IsHelperLane lowering and map it to int_spv_IsHelperLane in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/IsHelperLane.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
221	IsHelperLane	6.6	()

SPIR-V

OpIsHelperInvocationEXT:

Description:

Reserved.

Capability:
DemoteToHelperInvocationEXT

Reserved.

Word Count	Opcode	Results	Operands
3	5381	<id> Result Type	Result <id>

Test Case(s)

Example 1

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

export bool fn() {
    return IsHelperLane();
}

HLSL:

Syntax

bool IsHelperLane();

Type Description

Name	Template Type	Component Type	Size
ret	scalar	bool	1

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 6.6 and higher shader models	yes

Shader Stages

See also

• Intrinsic Functions (DirectX HLSL)
• See IsHelperLane

[damyanp]

@farzonl - this HLSL function was backported to older shader models where there wasn't necessarily a dxil op for it. The issue here needs to be updated to reflect this.