[X86] Combine (cmov (and/or (setcc) (setcc))) into (cmov (cmov)).

[X86] Combine (cmov (and/or (setcc) (setcc))) into (cmov (cmov)).

Fold and/or of setcc's to double CMOV:

(CMOV F, T, ((cc1 | cc2) != 0)) -> (CMOV (CMOV F, T, cc1), T, cc2)
(CMOV F, T, ((cc1 & cc2) != 0)) -> (CMOV (CMOV T, F, !cc1), F, !cc2)

When we can't use the CMOV instruction, it might increase branch
mispredicts.  When we can, or when there is no mispredict, this
improves throughput and reduces register pressure.

These can't be catched by generic combines, because the pattern can
appear when legalizing some instructions (such as fcmp une).

rdar://19767934
http://reviews.llvm.org/D7634

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231045 91177308-0d34-0410-b5e6-96231b3b80d8