Teach X86 MC instruction lowering that VMOVAPSrr and other VEX-encoded register to register moves should be switched from using the MRMSrcReg form to the MRMDestReg form if the source register is a 64-bit extended register and the destination register is not. This allows the instruction to be encoded using the 2-byte VEX form instead of the 3-byte VEX form. The GNU assembler has similar behavior.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177011 91177308-0d34-0410-b5e6-96231b3b80d8