If the instruction have match pattern, llvm-tblgen will infer the sideeffect bit from the match pattern and it works well.
If not, the tblgen will set it as true that hurt the scheduling.
PowerPC has some instructions that didn't specify the match pattern(i.e. LXSD etc), which is manually selected post-ra according
to the register pressure. We need to clear the sideeffect flag for these instructions.
Differential Revision: https://reviews.llvm.org/D69232
After implemented this hook, we will model the memory dependency in the scheduling dependency graph more precise,
and will have more opportunity to reorder the load/stores, as they didn't have the dependency at some condition
Differential Revision: https://reviews.llvm.org/D63804
llvm-svn: 364886