[llvm] [TableGen] Add InstrInfoEmitter options for operand type/size mappings (PR #125797)

[Rahul Joshi via llvm-commits]

jurahul wrote:

> > What's the measured impact of this change?
> 
> I don't have one. In a downstream backend I am working on though, I did notice that these type mappings generate quite a bit of code that is unused. For operand size mappings, its specific to X86 as it looks for X86MemOperand. So, we could potentially remove the option and just bail out if `getInstNamespace() != X86`, but that seemed less kosher than adding an option.

The compile time improvement will be in the noise :( Just for the AMDGPU instrinfo, "Emit operand type mappings" is 0.6% and and "Emit logical operand size mappings" is 0.2%. So not that much. So really, its removing cruft from the generated file that no one uses. I'll leave up to the reviewers if its worth it given extra options added.

I also found that GET_INSTRINFO_LOGICAL_OPERAND_TYPE_MAP is not used by any upstream backend. So we could potentially drop it completely, unless it was utility in a downstream backend.

https://github.com/llvm/llvm-project/pull/125797