[CodeGen] Fix problem with X86 byte registers in CriticalAntiDepBreaker

CriticalAntiDepBreaker was not correctly tracking defs of the high X86 byte
registers, leading to incorrect use of a busy register to break an
antidependence.

Fixes pr27681, and its duplicates pr27580, pr27804.

Differential Revision: http://reviews.llvm.org/D20456


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270935 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed