Implement the `atan2` HLSL Function #70096

llvm-beanz · 2023-10-24T19:12:09Z

Note atan2 has been identified as a potential generic llvm intrinsic:
Investigation: #87367
RFC: https://discourse.llvm.org/t/rfc-all-the-math-intrinsics/78294

  case TargetOpcode::G_FATAN2:
    return selectExtInst(ResVReg, ResType, I, CL::atan2, GL::Atan2);

Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/atan2.ll

DirectX

DXIL Opcode	DXIL OpName	Shader Model	Shader Stages
17	Atan	6.0	()

SPIR-V

Atan2:

Description:

Atan2

Arc tangent. Result is an angle, in radians, whose tangent is y / x.
The signs of x and y are used to determine what quadrant the angle
is in. The range of result values is [-π, π] . Result is undefined if
x and y are both 0.

The operand x and y must be a scalar or vector whose component type
is 16-bit or 32-bit 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
25	<id> y	<id> x

Test Case(s)

Example 1

//dxc atan2_test.hlsl -T lib_6_8  -enable-16bit-types -spirv -fspv-target-env=universal1.5 -fcgl -O0

export float4 fn(float4 p1, float4 p2) {
    return atan2(p1, p2);
}

HLSL:

Returns the arctangent of two values (x,y).

ret atan2(y, x)

Parameters

Item	Description
y	[in] The y value.
x	[in] The x value.

Return Value

The arctangent of (y,x).

Remarks

The signs of the x and y parameters are used to determine the quadrant of the return values within the range of -π to π. The atan2 HLSL intrinsic function is well-defined for every point other than the origin, even if y equals 0 and x does not equal 0.

Type Description

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

Requirements

Requirement	Value
Header	Corecrt_math.h

Issue: llvm#70096 Changes: - Doc updates: - `clang/docs/LanguageExtensions.rst' - Document the new elementwise atan2 builtin. - `llvm/docs/LangRef.rst' - Document the atan2 intrinsic - TableGen: - `clang/include/clang/Basic/Builtins.td' - Implement the atan2 builtin. - `llvm/include/llvm/IR/Intrinsics.td' - Create the atan2 intrinsic - Sema checking: - `clang/lib/Sema/SemaChecking.cpp' - Add generic sema checks to the atan2 builtin - `clang/lib/Sema/SemaHLSL` Add HLSL specifc sema checks to the atan2 builtin - `clang/lib/CodeGen/CGBuiltin.cpp' - invoke the atan2 intrinsic on uses of the builtin - `clang/lib/Headers/hlsl/hlsl_intrinsics.h' - Associate the atan2 builtin with the equivalent hlsl apis

Issue: llvm#70096 Changes: - `llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp` - Expand atan2 intrinsic using atan for DXIL.

Issue: llvm#70096 Changes: - `llvm/docs/GlobalISel/GenericOpcode.rst` - Document the G_FATAN2 opcode - `llvm/include/llvm/Support/TargetOpcodes.def` - Create a G_FATAN2 Opcode handler - `llvm/include/llvm/Target/GenericOpcodes.td` - Define the G_FATAN2 Opcode - `llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp` Map the atan2 intrinsic to G_FATAN2 Opcode - `llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp` - Map the G_FATAN2 opcode to the GLSL 4.5 and openCL atan2 instructions. - `llvm/lib/Target/SPIRV/SPIRVLegalizerInfo.cpp` - Define G_FATAN2 as a legal spirv target opcode.

Issue: llvm#70096 Changes: - Doc updates: - `clang/docs/LanguageExtensions.rst` - Document the new elementwise atan2 builtin. - `llvm/docs/LangRef.rst` - Document the atan2 intrinsic - TableGen: - `clang/include/clang/Basic/Builtins.td` - Implement the atan2 builtin. - `llvm/include/llvm/IR/Intrinsics.td` - Create the atan2 intrinsic - Sema checking: - `clang/lib/Sema/SemaChecking.cpp` - Add generic sema checks to the atan2 builtin - `clang/lib/Sema/SemaHLSL` Add HLSL specifc sema checks to the atan2 builtin - `clang/lib/CodeGen/CGBuiltin.cpp` - invoke the atan2 intrinsic on uses of the builtin - `clang/lib/Headers/hlsl/hlsl_intrinsics.h` - Associate the atan2 builtin with the equivalent hlsl apis