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From: William Tambe <tambewilliam@gmail.com>
Date: Tue, 22 Feb 2022 18:51:22 -0600
Message-ID: <CAF8i9mO_OcKPgMoW4DNOn_NVQXP5UQ8vSz0D8MuK8UopFEvkXA@mail.gmail.com>
Subject: Re: Make GCC move instructions between a multi-cycle instruction and
 the next instruction that depends on its result.
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: gcc-help <gcc-help@gcc.gnu.org>
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On Tue, Feb 22, 2022 at 6:24 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> On Tue, Feb 22, 2022 at 03:15:55PM -0600, William Tambe via Gcc-help wrote:
> [snip]
> > > Without above transformation, `add %4 %7` would cause the cpu to wait
> > > on `div %4 %5` when it could have executed instructions that do not
> > > depend on the result of "div".
> >
> > How to implement above transformation such that GCC moves instructions
> > between a multi-cycle instruction and the next instruction that
> > depends on its result ?
>
> GCC has a pretty advanced instruction scheduler.  You can start looking
> at <https://gcc.gnu.org/onlinedocs/gccint/Scheduling.html> for example?
>

Thank you for the pointer; could you suggest an existing example close
to what I am looking to implement that uses above TARGET_SCHED_* hooks
?

>
> Segher