Implement the `saturate` HLSL Function

[farzonl]

• Implement saturate clang builtin,
• Link saturate clang builtin with hlsl_intrinsics.h
• Add sema checks for saturate to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• Add codegen for saturate to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• Add codegen tests to clang/test/CodeGenHLSL/builtins/saturate.hlsl
• Add sema tests to clang/test/SemaHLSL/BuiltIns/saturate-errors.hlsl
• Create the int_dx_saturate intrinsic in IntrinsicsDirectX.td
• Create the DXILOpMapping of int_dx_saturate to 7 in DXIL.td
• Create the saturate.ll and saturate_errors.ll tests in llvm/test/CodeGen/DirectX/
• Create the int_spv_saturate intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the saturate lowering and map it to int_spv_saturate in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/saturate.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
7	Saturate	6.0	()

SPIR-V

FClamp:

Description:

FClamp

Result is min(max(x, minVal), maxVal). Result is undefined if
minVal > maxVal.The semantics used by min() and max() are those of
FMin and FMax.

The operands must all be a scalar or vector whose component type is
floating-point.

Result Type and the type of all operands must be the same type.
Results are computed per component.

Number	Operand 1	Operand 2	Operand 3	Operand 4
43	<id> x	<id> minVal	<id> maxVal

Test Case(s)

Example 1

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

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

HLSL:

Clamps the specified value within the range of 0 to 1.

ret saturate(x)

Parameters

Item	Description
x	[in] The specified value.

Return Value

The x parameter, clamped within the range of 0 to 1.

Type Description

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

Minimum Shader Model

This function is supported in the following shader models.

Shader Model	Supported
Shader Model 1 (DirectX HLSL) and higher shader models	yes

See also

Intrinsic Functions (DirectX HLSL)