Implement the WaveReadLaneFirst HLSL Function

[farzonl]

• Implement WaveReadLaneFirst clang builtin,
• Link WaveReadLaneFirst clang builtin with hlsl_intrinsics.h
• Add sema checks for WaveReadLaneFirst to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for WaveReadLaneFirst to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/WaveReadLaneFirst.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/WaveReadLaneFirst-errors.hlsl
• Create the int_dx_WaveReadLaneFirst intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_WaveReadLaneFirst to 118 in DXIL.td
• Create the WaveReadLaneFirst.ll and WaveReadLaneFirst_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_WaveReadLaneFirst intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the WaveReadLaneFirst lowering and map it to int_spv_WaveReadLaneFirst in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/WaveReadLaneFirst.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
118	WaveReadLaneFirst	6.0	('library', 'compute', 'amplification', 'mesh', 'pixel', 'vertex', 'hull', 'domain', 'geometry', 'raygeneration', 'intersection', 'anyhit', 'closesthit', 'miss', 'callable', 'node')

SPIR-V

OpGroupNonUniformBroadcastFirst:

Description:

Result is the Value of the invocation from the active
invocation with the lowest id in the group to all active
invocations in the group.

Result Type must be a scalar or vector of floating-point
type, integer type, or Boolean
type.

Execution is a Scope that identifies the group of
invocations affected by this command. It must be Subgroup.

The type of Value must be the same as Result Type.

Capability:
GroupNonUniformBallot

Missing before version 1.3.

Word Count	Opcode	Results	Operands
5	338	<id> Result Type	Result <id>	Scope <id> Execution	<id> Value

Test Case(s)

Example 1

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

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

HLSL:

Returns the value of the expression for the active lane of the current wave with the smallest index.

Syntax

<type> WaveReadLaneFirst(
   <type> expr
);

Parameters

expr

The expression to evaluate.

Return value

The resulting value is uniform across the wave.

Remarks

This function is supported from shader model 6.0 in all shader stages.

 

See also

Overview of Shader Model 6

Shader Model 6