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From: "klepikov.alex+bugs at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/54089] [SH] Refactor shift patterns
Date: Sat, 03 Jun 2023 15:43:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D54089

--- Comment #56 from Alexander Klepikov <klepikov.alex+bugs at gmail dot co=
m> ---
> > Regarding testsuite. There's execute fails, but this is due to lack of
> > multilib. I'll rebuild and retest.
> >=20
> > There's also fail in pr64345-1.c, in this function:
> > [...]
> >=20
> > But it looks more like it's not a fail, but an optimization.
>=20
> Yeah, that looks like an improvement.  There might be some SH specific te=
sts
> that scan for particular assembler outputs like that one.  Those tests wo=
uld
> need to be adjusted of course.

I checked and that one was the only one.

> In that test you can see the unnecessary push/pop of PR.  This is because
> initially it wanted to expand as a library call, but then your patterns
> decided to change the insns. This can or can't be avoided, depending on t=
he
> case.

That's an valuable observation, thank you! I found why. Sometimes 'collapsed
libcall' instruction is emitted in combine pass and 'clobber PR' is set the=
n. I
commented this out and checked that file and it seems to be OK. I will rerun
testsuite again to be sure.

Now regarding tests that fail on vanilla GCC and pass with patch. It looks =
like
something was changed in the middle of GCC and it started to produce other
instruction patterns that cannot be catched by existing isns and thus expan=
ded
to library calls. The patch simply fixed it.=