Implement the `distance` HLSL Function

[farzonl]

• implement distance in the hlsl_intrinsics.h
• Implement distance spirv target builtin in clang/include/clang/Basic/BuiltinsSPIRV.td
• Add a spirv fast path in hlsl_detail.h in the form

#if (__has_builtin(__builtin_spirv_distance))
  return __builtin_spirv_distance(...);
#else
  return ...; // regular behavior
#endif

• Add codegen for spirv distance builtin to EmitSPIRVBuiltinExpr in CGBuiltin.cpp
• Add HLSL codegen tests to clang/test/CodeGenHLSL/builtins/distance.hlsl
• Add SPIRV builtin codegen tests to clang/test/CodeGenSPIRV/Builtins/distance.c
• Add sema tests to clang/test/SemaHLSL/BuiltIns/distance-errors.hlsl
• Add spirv sema tests to clang/test/CodeGenSPIRV/Builtins/distance-errors.c
• Create the int_spv_distance intrinsic in IntrinsicsSPIRV.td
• In SPIRVInstructionSelector.cpp create the distance lowering and map it to int_spv_distance in SPIRVInstructionSelector::selectIntrinsic.
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/hlsl-intrinsics/distance.ll
• Create SPIR-V backend test case in llvm/test/CodeGen/SPIRV/opencl/distance.ll

DirectX

There are no DXIL opcodes found for distance.

SPIR-V

Distance:

Description:

Distance

Result is the distance between p0 and p1, i.e., length(p0 -
p1).

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

Result Type must be a scalar of the same type as the component type of
the operands.

Number	Operand 1	Operand 2	Operand 3	Operand 4
67	<id> p0	<id> p1

Test Case(s)

Example 1

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

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

HLSL:

Returns a distance scalar between two vectors.

ret distance(x, y)

Parameters

Item	Description
x	[in] The first floating-point vector to compare.
y	[in] The second floating-point vector to compare.

Return Value

A floating-point, scalar value that represents the distance between the x parameter and the y parameter.

Type Description

Name	Template Type	Component Type	Size
x	vector	float	any
y	vector	float	same dimension(s) as input x
ret	scalar	float	1

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

See also

Intrinsic Functions (DirectX HLSL)

[damyanp]

@farzonl - please rework issue to describe it being fully implemented in the header.