The X86 backend has a number of optimizations for SETCC nodes which use

arithmetic instructions. However, when small data types are used, a truncate
node appears between the SETCC node and the arithmetic operation. This patch
adds support for this pattern.

Before:
  xorl  %esi, %edi
  testb %dil, %dil
  setne %al
  ret

After:
  xorb  %dil, %sil
  setne %al
  ret

rdar://12081007

llvm-svn: 162160