Implement the `InterlockedExchange` HLSL Function

[farzonl]

• Implement InterlockedExchange clang builtin,
• Link InterlockedExchange clang builtin with hlsl_intrinsics.h
• Add sema checks for InterlockedExchange to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for InterlockedExchange to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/InterlockedExchange.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/InterlockedExchange-errors.hlsl
• Create the int_dx_InterlockedExchange intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_InterlockedExchange to 78 in DXIL.td
• Create the InterlockedExchange.ll and InterlockedExchange_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_InterlockedExchange intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the InterlockedExchange lowering and map it to int_spv_InterlockedExchange in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/InterlockedExchange.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
78	AtomicBinOp	6.0	()

SPIR-V

OpAtomicExchange:

Description:

Perform the following steps atomically with respect to any other atomic
accesses within Scope to the same location:

1. load through Pointer to get an Original Value,
2. get a New Value from copying Value, and
3. store the New Value back through Pointer.

The instruction’s result is the Original Value.

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

The type of Value must be the same as Result Type. The type of the
value pointed to by Pointer must be the same as Result Type.

Memory is a memory Scope.

Word Count	Opcode	Results	Operands
7	229	<id> Result Type	Result <id>	<id> Pointer	Scope <id> Memory	Memory Semantics <id> Semantics	<id> Value

Test Case(s)

Example 1

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

RWStructuredBuffer<int64_t> buffer : register(u0);
[numthreads(1, 1, 1)]
export void fn(uint3 dispatchThreadID : SV_DispatchThreadID, int64_t p1, int64_t p2) {
int index = dispatchThreadID.x;
    return InterlockedExchange(buffer[index], p1, p2);
}

Example 2

//dxc InterlockedExchange_1_test.hlsl -T lib_6_8 -enable-16bit-types -O0

RWStructuredBuffer<float> buffer : register(u0);
[numthreads(1, 1, 1)]
export void fn(uint3 dispatchThreadID : SV_DispatchThreadID, float p1, float p2) {
int index = dispatchThreadID.x;
    return InterlockedExchange(buffer[index], p1, p2);
}

Example 3

//dxc InterlockedExchange_2_test.hlsl -T lib_6_8 -enable-16bit-types -O0

RWStructuredBuffer<int> buffer : register(u0);
[numthreads(1, 1, 1)]
export void fn(uint3 dispatchThreadID : SV_DispatchThreadID, int p1, uint p2) {
int index = dispatchThreadID.x;
    return InterlockedExchange(buffer[index], p1, p2);
}

HLSL:

Assigns value to dest and returns the original value.

Syntax

void InterlockedExchange(
  in  R dest,
  in  T value,
  out T original_value
);

Parameters

dest [in]

Type: R

The destination address.

value [in]

Type: T

The input value.

original_value [out]

Type: T

The original value.

Return value

This function does not return a value.

Remarks

This operation can only be performed on scalar-typed resources and shared memory variables. There are two possible uses for this function. The first is when R is a shared memory variable type. In this case, the function performs the operation on the shared memory register referenced by dest. The second scenario is when R is a resource variable type. In this scenario, the function performs the operation on the resource location referenced by dest. This operation is only available when R is readable and writable.

Interlocked operations do not imply any memory fence/barrier.

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 5 and higher shader models	yes

 

This function is supported in the following types of shaders:

Vertex	Hull	Domain	Geometry	Pixel	Compute
x	x	x	x	x	x

 

See also

Intrinsic Functions

Shader Model 5