[Bug rtl-optimization/113597] [14 Regression] aarch64: Significant code quality regression since r14-8346-ga98d5130a6dcff

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113597

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 57212
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57212&action=edit
patch for debugging

Btw, I've used the attached to investigate other issues with the change.  It
will show the outcome of base_alias_check and find_base_term in dumps.

One issue is that we're much more dependent on MEM_EXPRs being present.

Before figuring there wouldn't be much important regressions the idea was to
instead of doing find_base_term have a known base value recorded in the
MEM_ATTRs, and as the only important ones should be the special ones for
argument frame and stack-based represent that by an enum (rather than
the other possibility of using ADDRESS).  I'll also note that for spill
slots we get around to use spill_slot_decl and set_mem_attrs_for_spill.

I've not yet convinced myself that the other special bases we have really
form a completely separate memory class.  But if they do then accesses
should do something similar there (but mind scheduling of frame related
instructions ...).

Argument stack slots are one important class, set up by init_alias_analysis.
But those are also backed by regular decls at times (but not always)?

assign_stack_temp "allocated" memory is another class, we're reusing
slots during RTL expansion and they get (even if shared) a specific
alias set.  I don't think we ever release those temps and say re-use
the space for spilling so assigning a different decl to each slot
should eventually work.