[X86] Sort the static memory folding tables by reg opcode. Remove the reg->mem...

[X86] Sort the static memory folding tables by reg opcode. Remove the reg->mem DenseMaps in favor of binary search.

With the static tables sorted we can binary search them directly for reg->mem lookups. This removes 6 DenseMaps that had to be created when X86InstrInfo is constructed.

We still have one Mem->Reg DenseMap for the reverse direction. This is created just as before by walking the reg->mem arrays to populate it.

Differential Revision: https://reviews.llvm.org/D48527

llvm-svn: 335501