From: Alan Modra <amodra@gmail.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [RS6000] Power10 libffi fixes
Date: Thu, 24 Sep 2020 13:11:02 +0930 [thread overview]
Message-ID: <20200924034102.GJ5452@bubble.grove.modra.org> (raw)
In-Reply-To: <20200923001657.GQ28786@gate.crashing.org>
On Tue, Sep 22, 2020 at 07:16:57PM -0500, Segher Boessenkool wrote:
> Hi!
>
> On Tue, Sep 22, 2020 at 10:00:11AM +0930, Alan Modra wrote:
> > gcc/
> > * config/rs6000/rs6000-c.c (rs6000_target_modify_macros):
> > Conditionally define __PCREL__.
>
> Please do that as a separate (earlier) patch (because it *is*, and to
> simplify backports, etc).
Done.
> > libffi/
> > * src/powerpc/linux64.S (ffi_call_LINUX64): Don't emit global
> > entry when __PCREL__. Call using @notoc.
> > (ffi_closure_LINUX64, ffi_go_closure_linux64): Likewise.
>
> This is okay for trunk, and for backports (possibly expedited, talk
> with Peter for what is wanted/needed for AT).
I've fixed the changelog, a comment, and added a nop after bl for the
old calls without @notoc. While there really isn't a need for the
nops in libffi.so since the callee is hidden visibility, there is a
miniscule chance that a static libffi.a user has a very large TOC and
somehow manages to have ffi_call_LINUX64 and ffi_prep_args64 using
different TOC pointers. In that case the linker would arrange the
call to go via a toc-adjusting stub and want to replace the nop with a
toc restore.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2020-09-24 3:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 0:30 Alan Modra
2020-09-23 0:16 ` Segher Boessenkool
2020-09-24 3:41 ` Alan Modra [this message]
2020-09-24 5:39 ` Alan Modra
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