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Date: Tue, 27 Oct 2015 15:20:00 -0000
Message-ID: <CAMe9rOrOkzkY13Jja9VqNx536jqZZcuVYYaxOt6XcZGcP1gR+w@mail.gmail.com>
Subject: Re: PING: [PATCH] PR target/67215: -fno-plt needs improvements for x86
From: "H.J. Lu" <hjl.tools@gmail.com>
To: Ramana Radhakrishnan <ramana.radhakrishnan@foss.arm.com>
Cc: Jiong Wang <jiong.wang@foss.arm.com>, Bernd Schmidt <bschmidt@redhat.com>, 	GCC Patches <gcc-patches@gcc.gnu.org>
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On Tue, Oct 27, 2015 at 7:34 AM, Ramana Radhakrishnan
<ramana.radhakrishnan@foss.arm.com> wrote:
>
>>
>> OK, then it's fairly x86-64 specific optimization, because we can't do "=
call *mem" in
>> aarch64 and some other targets.
>
> It is a fairly x86_64 specific optimization and doesn't apply to AArch64.
>
> The question really is what impact does removing the generic code handlin=
g have on aarch64 - is it a no-op or not for the existing -fno-plt implemen=
tation in the AArch64 backend ? The only case that is of interest is the bi=
t below in calls.c and it looks like that may well be redundant with the lo=
gic in the backend already, but I have not done the full analysis to convin=
ce myself that the code in the backend is sufficient.
>
> -  && (!flag_plt
> -              || lookup_attribute ("noplt", DECL_ATTRIBUTES (fndecl_or_t=
ype)))
> -          && !targetm.binds_local_p (fndecl_or_type))
>

-fno-plt is a backend specific optimization and should be handled
in backend.

--=20
H.J.