Implement the `fmod` HLSL Function

[farzonl]

• [ ] Implement fmod clang builtin,
• [ ] Link fmod clang builtin with hlsl_intrinsics.h
• [ ] Add sema checks for fmod to CheckHLSLBuiltinFunctionCall in SemaChecking.cpp
• [ ] Add codegen for fmod to EmitHLSLBuiltinExpr in CGBuiltin.cpp
• [ ] Add codegen tests to clang/test/CodeGenHLSL/builtins/fmod.hlsl
• [ ] Add sema tests to clang/test/SemaHLSL/BuiltIns/fmod-errors.hlsl
• [ ] Create the int_dx_fmod intrinsic in IntrinsicsDirectX.td
• [ ] Create the DXILOpMapping of int_dx_fmod to 6 in DXIL.td
• [ ] Create the fmod.ll and fmod_errors.ll tests in llvm/test/CodeGen/DirectX/
• [ ] Create the int_spv_fmod intrinsic in IntrinsicsSPIRV.td
• [ ] In SPIRVInstructionSelector.cpp create the fmod lowering and map it to int_spv_fmod in SPIRVInstructionSelector::selectIntrinsic.
• [ ] Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/fmod.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
6	FAbs	6.0	()

SPIR-V

OpFRem:

Description:

The floating-point remainder whose sign matches the sign of Operand 1.

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

The types of Operand 1 and Operand 2 both must be the same as Result Type.

Results are computed per component. The resulting value is undefined if Operand 2 is 0. Otherwise, the result is the remainder r of Operand 1 divided by Operand 2 where if r ≠ 0, the sign of r is the same as the sign of Operand 1.

Word Count	Opcode	Results	Operands
5	140	<id> Result Type	Result <id>	<id> Operand 1	<id> Operand 2

Test Case(s)

Example 1

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

export float4 fn(float4 p1, float4 p2) {
    return fmod(p1, p2);
}

HLSL:

Returns the floating-point remainder of x/y.

ret fmod(x, y)

Parameters

Item	Description
x	[in] The floating-point dividend.
y	[in] The floating-point divisor.

Return Value

The floating-point remainder of the x parameter divided by the y parameter.

Remarks

The floating-point remainder is calculated such that x = i * y + f, where i is an integer, f has the same sign as x, and the absolute value of f is less than the absolute value of y.

Type Description

Name	Template Type	Component Type	Size
x	scalar, vector, or matrix	float	any
y	same as input x	float	same dimension(s) as input x
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 2 (DirectX HLSL) and higher shader models	yes
Shader Model 1 (DirectX HLSL)	vs_1_1

Requirements

Requirement	Value
Header	Corecrt_math.h

See also

[**Intrinsic Functions (DirectX HLSL)**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md)

[farzonl]

Note to implementer it is very likely we don't need to create int_dx_fmod and int_spv_fmod target specific intrinsics if we can use frem

[lizhengxing]

I'll work on this task.