[MachineOutliner][AArch64] WA for multiple stack fixup cases in MachineOutliner.
In cases where MachineOutliner candidates either are:
* noreturn
* have calls with no available LR or free regs
* Don't use SP
we can end up hitting stack fixup code for the caller and the callee for
a FrameID of MachineOutlinerDefault. This triggers the assert:
`assert(OF.FrameConstructionID != MachineOutlinerDefault &&
"Can only fix up stack references once");`
in AArch64InstrInfo.cpp. This assert exists for now because a lot of the
fixup code is not tested to handle fixing up more than once and needs
some better checks and enhancements to avoid potentially generating
illegal code.
I've filed a Bugzilla report to track this until these cases are handled
by the AArch64 MachineOutliner: https://bugs.llvm.org/show_bug.cgi?id=46767
This diff detects cases that will cause these multiple stack fixups and
prune the Candidates from `RepeatedSequenceLocs`.
Differential Revision: https://reviews.llvm.org/D83923