Add support for x86 CMPEQSS and friends. These instructions do a

Add support for x86 CMPEQSS and friends.  These instructions do a
floating-point comparison, generate a mask of 0s or 1s, and generally
DTRT with NaNs.  Only profitable when the user wants a materialized 0
or 1 at runtime.  rdar://problem/5993888

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132404 91177308-0d34-0410-b5e6-96231b3b80d8