[llvm] [LLVMABI] Implement the ABI Typesystem (PR #158329)

[via llvm-commits]

vortex73 wrote:

> > > I appreciate the elegance of having a type system that eliminates differences that don't really matter at the ABI level, but having to allocate a bunch of memory to translate types to a new representation that's used for a few cycles while we call this portable library seems like a pretty high amount of overhead.
> > 
> > 
> > The prototype shows compile-time impact of [<0.1%](https://llvm-compile-time-tracker.com/compare.php?from=5886a276ed24c2cd936e602441365bb0bbe5ef40&to=a419e44cee5a9de7d3720133c3ad98b0174923e6&stat=instructions:u) at -O0, even without any performance optimization work. Isn't that pretty negligible in practice?
> 
> Those measurements show a .6% compile time impact. Are you looking at the file sizes?
> 
> Also, this change is not supposed to actually change the emitted instructions, so something's pretty clearly up there.

I'm referring to instructions.
Also the isn't the increase in instruction count mainly due to additional code being compiled, new code paths etc?

https://github.com/llvm/llvm-project/pull/158329