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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/54089] [SH] Refactor shift patterns
Date: Fri, 16 Jun 2023 21:58:06 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D54089

--- Comment #76 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Alexander Klepikov from comment #75)
> I found that patch incorrectly works when '-O0 -fmove-loop-invariants' fl=
ags
> are set. Stock loop optimization passes do not run when '-O0' is specified
> desipte '-fmove-loop-invariants' is set. I'll do the same and recheck aga=
in.

It'd be good if the newly added passes are ran only with -O2 or higher.  Or
even better, if we can find a way to enable them only when actually needed.=
=20
E.g. when it's splitting a shift insn that will potentially need the loop
optimizations again, set a flag in the function.

One way to do that could be adding SH specific function context class/struc=
t to
store some per-function data for the compilation process.  Right now we'd h=
ave
only one entry, that is whether to run the additional passes again or not.=
=20
This per-function 'SH context' can be stored as a global variable in sh.cc.=
=20
Then override 'set_current_function' in the backend to reset the SH specific
per-function context.

However, to get better test coverage, it's better first let the additional =
loop
passes run all the time to uncover any potential issues.  Later the above c=
an
be added as a supplementary optimization.=