currently, the implementation of AArch64 prologue/epilogue expand
hooks are a bit unclean.
the major issues are:
* when pushing callee-saved registers, register offset are
calculated by ad-hoc code instead of referencing offset
table initialized in aarch64_layout_frame.
* FP/LR push/restore are done by ad-hoc code, should be
unified with other registers.
* various duplicated code for pushing/restoring core and
vectore registers.
* sub-optimal instruction sequences generated for some
scenarios.
the following patch set trying to address above issues in
an incremental way, that the review could be easier.
no regression on aarch64-none-elf little/big endian bare-metal full test.
bootstrap OK on aarch64.
ok to install?
thanks.
-- Jiong
