[HLSL] Implement _split double_ scenario for `asuint` in HLSL

[joaosaffran]

Implement asuint clang builtin,splitdouble,

• Link asuint clang builtin with hlsl_intrinsics.h
• Add sema checks for asuint to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for asuint to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Use HLSL bit_cast to implement the SPIRV code gen
• Add codegen tests to clang/test/CodeGenHLSL/builtins/asuint-splitdouble.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/asuint-splitdouble-errors.hlsl

This will implement the missing DXIL requirements for #70097

DXIL

Opcode	DXIL OpName	Shader Model	Shader Stages	Description
102	SplitDouble	6.0	()	splits a double into low and high parts

SPIR-V

There is no support for asuint when targeting SPIR-V.

asuint

Interprets the bit pattern of x as an unsigned integer.

ret asuint(x)

Test Case(s)

Example 1

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

export uint4 fn(double4 p1, uint4 p2, uint4 p3) {
    asuint(p1, p2, p3);
    return p3;
}

Parameters

Item	Description
x	[in] The input value.

Return Value

The input interpreted as an unsigned integer.

Type Description

Name	Template Type	Component Type	Size
x	scalar, vector, or matrix	float, int	any
ret	same as input x	uint	same dimension(s) as input x

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 4 and higher shader models	yes
Shader Model 3 (DirectX HLSL)	no
Shader Model 2 (DirectX HLSL)	no
Shader Model 1 (DirectX HLSL)	no

See also

Intrinsic Functions (DirectX HLSL)