[AArch64] Fold more spilled/refilled COPYs.

Summary:
Make AArch64InstrInfo::foldMemoryOperandImpl more general by folding all
full COPYs between register classes of the same size that are either
spilled or refilled.

Reviewers: MatzeB, qcolombet

Subscribers: aemerson, rengolin, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D27271

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288439 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed