From: Jeff Law <law@redhat.com>
To: David Edelsohn <dje.gcc@gmail.com>, Steve Ellcey <sellcey@imgtec.com>
Cc: "Martin Liška" <mliska@suse.cz>, "Jan Hubicka" <hubicka@ucw.cz>,
"GCC Patches" <gcc-patches@gcc.gnu.org>,
"Ramana Radhakrishnan" <ramana.radhakrishnan@arm.com>,
"Richard Earnshaw" <Richard.Earnshaw@arm.com>
Subject: Re: Question about patch for PR bootstrap/65150 (identical functions)
Date: Fri, 08 May 2015 19:10:00 -0000 [thread overview]
Message-ID: <554D0A00.4000002@redhat.com> (raw)
In-Reply-To: <CAGWvnynmRq2CCUzj_ND0tGzXZLYNVdXOPVV_jKkFwm4UpBdYYQ@mail.gmail.com>
On 05/08/2015 01:07 PM, David Edelsohn wrote:
>>>> Steve Ellcey wrote:
>>
>> After your change GCC sees that the code for f1 and f2 are identical
>> so it replaced the body of f2 with a call to f1. This optimization will
>> save space but it is not going to be faster because any call to f2 will
>> now include an extra call/return. Do other platforms have this same issue
>> or is there a way to make f2 an alias for f1 on other targets so no extra
>> call is needed? I looked around to see if there was a target function or
>> macro that is used to make one function an alias of another but I didn't
>> see anything.
>
> This probably is not good for POWER, and probably not for ARM, in fact
> probably not good for most RISC architectures.
But isn't this code going to be creating aliases when the output format
supports them -- which avoids the call/return overheads?
Which might argue that if we don't have aliases, then ICF might need to
be a -Os thing.
jeff
next prev parent reply other threads:[~2015-05-08 19:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-08 19:07 David Edelsohn
2015-05-08 19:10 ` Jeff Law [this message]
2015-05-08 19:35 ` Jakub Jelinek
2015-05-08 21:58 ` Jan Hubicka
2015-05-08 22:56 ` Bernhard Reutner-Fischer
-- strict thread matches above, loose matches on Subject: below --
2015-05-08 17:50 Steve Ellcey
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