When expanding neon pseudo stores, it may miss the implicit uses of sub
regs, which may cause post RA scheduler reorder instructions that
breakes anti dependency.
For example:
VST1d64QPseudo %R0<kill>, 16, %Q9_Q10, pred:14, pred:%noreg
will be expanded to
VST1d64Q %R0<kill>, 16, %D18, pred:14, pred:%noreg;
An instruction that defines %D20 may be scheduled before the store by
mistake.
This patches adds implicit uses for such case. For the example above, it
emits:
VST1d64Q %R0<kill>, 8, %D18, pred:14, pred:%noreg, %Q9_Q10<imp-use>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199282 91177308-0d34-0410-b5e6-96231b3b80d8
