[DirectX] Introduce llvm.dx.bufferGetDimensions and lower it to getDimensions dxil ops

[hekota]

We need LLVM intrinsic for GetDimensions which will be lowered to the op.dx.getDimensions dxil operations. These will be used on structured buffers.

https://godbolt.org/z/bz7zxsf5n

[damyanp]

@hekota - can you compare this to #101579 please and figure out which one we should go forward with?

[farzonl]

• In clang/include/clang/Basic/Builtins.td Add

def HLSLBufferGetDimensions : LangBuiltin<"HLSL_LANG"> {
  let Spellings = ["__builtin_hlsl_buffer_get_dimensions"];
  let Attributes = [NoThrow, CustomTypeChecking];
  let Prototype = "void(...)";
}

• Prototype is a struct return but no way to represent that in Builtins.td
• Other Struct return builtins have CustomTypeChecking
• The form of the intrinsic is:

struct Astruct {float a;};
RWStructuredBuffer<Astruct > Buf : register(u0);
uint count, stride;
Buf.GetDimensions(count, stride);

It should generate DXIL that looks like so.

%8 = call %dx.types.Dimensions @dx.op.getDimensions(i32 72, %dx.types.Handle %7, i32 undef)
%9 = extractvalue %dx.types.Dimensions %8

• In HLSLExternalSemaSource.cpp create a addGetDimensionsMethods function that defines a GetDimensions TokenKind::identifier.
• In HLSLExternalSemaSource.cpp call addGetDimensionsMethods for 23 types:
  • Texture1D
  • Texture1DArray
  • Texture2D
  • Texture2DMS
  • Texture2DArray
  • Texture2DArrayMS
  • Texture3D
  • TextureCUBE
  • TextureCUBEArray
  • Buffer
  • RWTexture1D
  • RWTexture1DArray
  • RWTexture2D
  • RWTexture2DArray
  • RWTexture2DMS
  • RWTexture2DMSArray
  • RWTexture3D
  • RWBuffer
  • ByteAddressBuffer
  • RWByteAddressBuffer
  • StructuredBuffer
  • RWStructuredBuffer
  • AppendStructuredBuffer,
  • ConsumeStructuredBuffer
• In llvm/include/llvm/IR/IntrinsicsDirectX.td and llvm/include/llvm/IR/IntrinsicsSPIRV.td define an intrinsic whose first parameter is the buffer handle and whose return type is an anonymous struct. The struct return type is used to represent out parameters for the above count and stride. An Example of this was done in the splitDouble pr.
• Add the intrinsic toggle preprocessor macro to clang/lib/CodeGen/CGHLSLRuntime.h.
• Add the builtin to intrinsic mapping in clang/lib/CodeGen/CGBuiltin.cpp. should be a standard Builder.CreateIntrinsic calling
  CGM.getHLSLRuntime().getBufferGetDimensionsIntrinsic(), where the first argument is the buffer handle Value *ResHandle = EmitScalarExpr(E->getArg(0));
• TODO investigate SEMA requirements
• TODO we likely need backend changes to convert from named structs to anonymous structs gracefully in DXIL.
• In DXIL.td add a def DimensionsTy : : DXILOpParamType; to map out params.
• In DXILOpBuilder.h define a getter for %dx.types.Dimensions.
• In DXILOpBuilder.cpp implemented the getter getDimensionsType which returns a StructType.
• The struct must be made up of 4 integers not all integers will be set depending on handle. see docs

[farzonl]

There are 54 cases of GetDimensions we need to support. Below is how they are used per Handle type.

Texture1D

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width) : resinfo_o;
• void [[]] GetDimensions(out float_like width) : resinfo_o;

Texture1DArray

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 elements, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 elements, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 elements) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 elements) : resinfo_o;

Texture2D

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 height, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 height, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 height) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height) : resinfo_o;

Texture2DMS

• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type2 samples) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type2 samples) : resinfo_o;

Texture2DArray

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 height, out $type2 elements, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 height, out $type2 elements, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 elements) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 elements) : resinfo_o;

Texture2DArrayMS

• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 elements, out $type1 samples) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 elements, out $type1 samples) : resinfo_o;

Texture3D

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 height, out $type2 depth, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 height, out $type2 depth, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 depth) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 depth) : resinfo_o;

TextureCUBE

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 height, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 height, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 height) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height) : resinfo_o;

TextureCUBEArray

• void [[]] GetDimensions(in uint x, out uint_only width, out $type2 height, out $type2 elements, out $type2 levels) : resinfo_uint;
• void [[]] GetDimensions(in uint x, out float_like width, out $type2 height, out $type2 elements, out $type2 levels) : resinfo;
• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 elements) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 elements) : resinfo_o;

Buffer

• void [[]] GetDimensions(out uint_only width) : bufinfo;

RWTexture1D

• void [[]] GetDimensions(out uint_only width) : resinfo_o;
• void [[]] GetDimensions(out float_like width) : resinfo_o;

RWTexture1DArray

• void [[]] GetDimensions(out uint_only width, out $type1 elements) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 elements) : resinfo_o;

RWTexture2D

• void [[]] GetDimensions(out uint_only width, out $type1 height) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height) : resinfo_o;

RWTexture2DArray

• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 elements) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 elements) : resinfo_o;

RWTexture2DMS

• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type2 samples);
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type2 samples);
  RWTexture2DMSArray
  -void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 elements, out $type1 samples);
  -void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 elements, out $type1 samples);

RWTexture3D

• void [[]] GetDimensions(out uint_only width, out $type1 height, out $type1 depth) : resinfo_uint_o;
• void [[]] GetDimensions(out float_like width, out $type1 height, out $type1 depth) : resinfo_o;

RWBuffer

• void [[]] GetDimensions(out uint_only width) : bufinfo;

ByteAddressBuffer

• void [[]] GetDimensions(out uint_only width) : bufinfo;

RWByteAddressBuffer

• void [[]] GetDimensions(out uint_only width) : bufinfo;

StructuredBuffer

• void [[]] GetDimensions(out uint_only count, out uint_only stride) : bufinfo;

RWStructuredBuffer

• void [[]] GetDimensions(out uint_only count, out uint_only stride) : bufinfo;

AppendStructuredBuffer

• void [[]] GetDimensions(out uint_only count, out uint_only stride) : bufinfo;

ConsumeStructuredBuffer

• void [[]] GetDimensions(out uint_only count, out uint_only stride) : bufinfo;