Newer ppc supports unaligned memory access, it reduces the cost of unaligned memory access significantly. This patch handles this case in PPCTTIImpl::getMemoryOpCost. This patch fixes pr31492. Differential Revision: https://reviews.llvm.org/D28630 This is resubmit of r292680, which was reverted by r293092. The internal application failures were actually caused by a source code bug. llvm-svn: 295506