[Hexagon] Simplify A4_rcmp[n]eqi R, 0

Consider cases when register R is known to be zero/non-zero, or when it
is defined by a C2_muxii instruction.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338251 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed