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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/111267] [14 Regression] Codegen regression
 from i386 argument passing changes
Date: Mon, 22 Jan 2024 09:11:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111267

--- Comment #12 from Richard Sandiford <rsandifo at gcc dot gnu.org> ---
I don't object to the patch, but for the record: the current heuristics go =
back
a long way.  Although I reworked the pass to use rtl-ssa a few years ago, I
tried as far as possible to preserve the old heuristics (tested by making s=
ure
that there were no unexplained differences over a large set of targets).

I wouldn't characterise the old heuristics as a logic error.  Although I di=
dn't
write them, my understanding is that they were being deliberately conservat=
ive,
in particular due to the risk of introducing excess register pressure.

So this change seems potentially quite invasive for stage 4.  Perhaps it'll
work out =E2=80=94 if so, great!  But if there is some fallout, I think we =
should lean
towards reverting the patch and revisiting in GCC 15.=