[PATCH] D20456: [CodeGen] Fix problem with X86 byte registers in CriticalAntiDepBreaker

[Matthias Braun via llvm-commits]

MatzeB added a comment.

I don't understand the nature of the bug with the explanation given here (and I don't know much about this pass). Why do you need this double loop, would iterating over the register alias work as well? The double loop here also seems to requires quadratic runtime in the depth of the sub/super register graph.

Based on the comment in the source it is not clear to me why we have to include alias registers into the KeepRegs set that are not touched by the instruction.


http://reviews.llvm.org/D20456