[libspirv] Fix image built-in mangled name

[wenju-he]

Combination of 5aa39a7 and 5947c2a caused new fail: Unable to demangle name: _Z23__spirv_ImageArrayFetchIDv2_cmFETCH_COORD_2_2_c

[Maetveis]

Just for my own understanding and to help other reviewers:

From the Itanium C++ ABI, Section 5.1.5 Type encodings:

Builtin types are represented by single-letter codes:

  <builtin-type> ::= v	# void
                 ::= w	# wchar_t
                 ::= b	# bool
                 ::= c	# char**
                 ::= a	# signed char
                 ::= h	# unsigned char
 (...)

So this change is due to the signed char -> char change in 5947c2a

[Maetveis]

LGTM.

[Maetveis]

I am wondering though, it would be nice to get away from mangling any symbols by hand, is that something you're looking to do @wenju-he?

[wenju-he]

I am wondering though, it would be nice to get away from mangling any symbols by hand, is that something you're looking to do @wenju-he?

@Maetveis I don't have plan to update ptx image builtin names. IMO ideally they should use/implement SPIR-V builtin rather than templated symbols.

[Maetveis]

@Maetveis I don't have plan to update ptx image builtin names. IMO ideally they should use/implement SPIR-V builtin rather than templated symbols.

But isn't template based mangling standard for some SPIR-V builtins? I see that there seem to be some Intel extensions like ImageFetchArray, but that's not the only templated symbol.

Maybe we could explore using C++ for these functions, the llvm libc and libc++ is already using it with the NVPTX target.

[wenju-he]

SPIR-V image builtins don't use templates.

Maybe we could explore using C++ for these functions, the llvm libc and libc++ is already using it with the NVPTX target.

This is a good direction for the PTX image builtin implementation which is templated. I'm not sure if SPIR-V builtins follow that same pattern.