support tile builtins

[g4titanx]

this pr fixes#563

[antoyo]

Please also enable the tile tests by adressing this comment.

[g4titanx]

@antoyo i need some clarity on impl. the tile intrinsics. currently, I see a few possible approaches:

1. Using get_target_builtin_function, but this fails with "Cannot find target builtin" errors since these don't have GCC builtin equivalents.

2. Creating custom functions with inline assembly, something like:

"llvm.x86.ldtilecfg" => {let name = "__rustc_tile_ldtilecfg";let func = cx.context.new_function(None,FunctionType::Internal,
cx.type_void(),&[/* params */],
name,false,);}

[antoyo]

Yeah, get_target_builtin_function won't work.

Perhaps your solution #2 would be the simplest (if that works). You could add the attribute AlwaysInline to make sure it's efficient.

Otherwise, I see another solution involving changing the type Function to an enum that would either take a Function or inline asm, but that might be a lot of work, so I would go with #2 if that works.

[rustbot]

☔ The latest upstream changes (possibly #863) made this pull request unmergeable. Please resolve the merge conflicts.