[AArch64 ] Generate a BFXIL from 'or (and X, Mask0Imm),(and Y, Mask1Imm)'.

Mask0Imm and ~Mask1Imm must be equivalent and one of the MaskImms is a shifted
mask (e.g., 0x000ffff0).  Both 'and's must have a single use.

This changes code like:

  and w8, w0, #0xffff000f
  and w9, w1, #0x0000fff0
  orr w0, w9, w8

into

  lsr w8, w1, #4
  bfi w0, w8, #4, #12

llvm-svn: 270063