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Re: Loop peeling
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Evandro Menezes <e dot menezes at samsung dot com>, Jan Hubicka <hubicka at ucw dot cz>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Wed, 29 Oct 2014 10:32:45 +0100
- Subject: Re: Loop peeling
- Authentication-results: sourceware.org; auth=none
- References: <033101cff2c7$96bff550$c43fdff0$ at samsung dot com>
On Tue, Oct 28, 2014 at 4:55 PM, Evandro Menezes <firstname.lastname@example.org> wrote:
> While doing some benchmark flag mining on AArch64, I noticed that
> -fpeel-loops was a mined option often. As a matter of fact, when using it
> always, even without FDO, it seemed to raise most benchmarks and to leave
> almost all of the rest flat, with a barely noticeable cost in code-size. It
> seems to me that it might be safe enough to be implied perhaps at -O3. Is
> there any reason why this never came into being?
Not sure, but peeling is/was very stupid (peeling 8 times unconditionally
or not at all). At least without FDO (and with -fprofile-use it is enabled).
Similar case for -funroll-loops.
For GCC 5 peeling now moved to GIMPLE, so maybe things changed
for that (but I'd doubt that). Honza?
> Thank you,
> Evandro Menezes Austin, TX