[llvm] [X86] Don't always separate conditions in `(br (and/or cond0, cond1))` into separate branches (PR #81689)

[via llvm-commits]

goldsteinn wrote:

> > Modest improvement on clang bootstrap build:
> > https://llvm-compile-time-tracker.com/compare.php?from=79ce933114e46c891a5632f7ad4a004b93a5b808&to=978278eabc0bafe2f390ca8fcdad24154f954020&stat=cycles
> > Average stage2-O3: 0.59% Improvement (cycles)
> > Average stage2-O0-g: 1.20% Improvement (cycles)
> 
> FWIW, this is most likely noise. At least I didn't see any stable improvement to cycles after this change landed.

Ah, yeah looked through, the didn't realize cycle variance was so high. Ill run SPEC locally and update message.

https://github.com/llvm/llvm-project/pull/81689