This patch adds the X86FixupLEAs pass, which will reduce instruction
latency for certain models of the Intel Atom family, by converting
instructions into their equivalent LEA instructions, when it is both
useful and possible to do so.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180573 91177308-0d34-0410-b5e6-96231b3b80d8
revert r179735, it has no testcases, and doesn't really make sense.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180574 91177308-0d34-0410-b5e6-96231b3b80d8