[llvm] [CodeGenPrepare] sinkCmpExpression - don't sink larger than legal integer comparisons (PR #166778)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> > Would it not expected to be generally profitable to sink a 64bit compare on a 32bit architecture?
> 
> Maybe, but we're keeping 4 registers in flight vs a single result, and it gets even messier if that involves splitting loads or vector - I'll try adding some extra logic based on how many different places the comparison result (and maybe the operands) are used.

@davemgreen I've added a constraint to only sink if we only uses the comparison in other BBs

https://github.com/llvm/llvm-project/pull/166778