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Re: [PATCHv2][PING^2][PR 56727] Bypass PLT for recursive calls

From: Yuri Gribov <tetra2005 at gmail dot com>
To: Jan Hubicka <hubicka at ucw dot cz>
Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
Date: Tue, 18 Jul 2017 09:26:56 +0100
Subject: Re: [PATCHv2][PING^2][PR 56727] Bypass PLT for recursive calls
Authentication-results: sourceware.org; auth=none
References: <CAJOtW+7RqLrkyNywgZFZ2GbintGAz6bitoAoCDYiiiiEt602_g@mail.gmail.com> <20170717092719.GB33905@kam.mff.cuni.cz>

On Mon, Jul 17, 2017 at 10:27 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> Hi all,
>>
>> This is a new version of previous patch
>> (https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00020.html), fixed
>> after Rainer's remarks.
> Hi,
> the patch looks OK, but I wonder why you included can_be_discarded check?
> If function is in comdat I believe the optimization still can happen.
> Perhaps you only want to check DECL_EXTERNAL?

TBH I was inspired by can_replace_by_local_alias which prohibits local
alias for discardable functions.  But I agree that situation here is
different and it's indeed not needed (if function is discarded, it
does not matter whether we optimized recursive calls).

Could you elaborate why we still need DECL_EXTERNAL though?

-Y

Follow-Ups:
- [PATCH] Fix wrong condition in ipa-visibility.c (PR ipa/81520).
  - From: Martin Liška

References:
- [PATCHv2][PING^2][PR 56727] Bypass PLT for recursive calls
  - From: Yuri Gribov
- Re: [PATCHv2][PING^2][PR 56727] Bypass PLT for recursive calls
  - From: Jan Hubicka

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