On Fri, Mar 21, 2025 at 02:00:18PM +0100, Jakub Jelinek wrote:
> I have some concerns:
> 1) I wonder if there is a guarantee that first_call_insn if non-NULL will be
> always in between curr_insn and usage_insn when call_save_p; I'd hope
> yes because if usage_insn is before first_call_insn in the ebb,
> presumably it wouldn't need to find call save regs because the range
> wouldn't cross any calls
> 2) I wonder whether it wouldn't be better instead of inserting the saves
> before first_call_insn insert it at the start of the bb containing that
> call (after labels of course); emitting it right before a call could
> mislead code looking for argument slot initialization of the call
Note, if we'd insert after labels of the bb containing first_call_insn
rather than before first_call_insn, perhaps verification that 1) is
guaranteed could be done through a dominance check. Except that ira.cc
seems to free_dominance_info (CDI_DOMINATORS) and nothing in lra* seems to
compute or do anything with CDI_DOMINATORS. Any other way to find out
cheaply what bb is earlier and what bb later within the ebb?
Jakub
