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From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: [PATCH] arm: avoid conditional branch to PLT in sigsetjmp.s
Date: Sat, 7 Dec 2019 13:03:05 -0500	[thread overview]
Message-ID: <20191207180305.GB1666@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAJ86T=V8Pu54XX1waFQT7+w_Z_2TTuNQk4e6jRcGLvQZi9Q7ww@mail.gmail.com>

On Thu, Nov 21, 2019 at 12:54:41PM -0800, Andre McCurdy wrote:
> On Wed, Sep 18, 2019 at 12:54 PM Rich Felker <dalias@libc.org> wrote:
> > On Wed, Sep 18, 2019 at 10:52:13AM -0700, Andre McCurdy wrote:
> > > On Wed, Sep 18, 2019 at 7:29 AM Khem Raj <raj.khem@gmail.com> wrote:
> > > > On Tue, Sep 17, 2019 at 11:04 PM Andre McCurdy <armccurdy@gmail.com> wrote:
> > > > >
> > > > > The R_ARM_THM_JUMP19 relocation type generated for the original code
> > > > > when targeting Thumb 2 is not supported by the gold linker:
> > > > >
> > > > >  | .../arm-oe-linux-musleabi/9.2.0/ld: error: conditional branch to PLT in THUMB-2 not supported yet.
> > > > >  | src/signal/arm/sigsetjmp.s:9: error: unexpected opcode while processing relocation R_ARM_THM_JUMP19
> > > >
> > > > if it is thumb2 specific another option could be to use `it eq` before
> > > > beq which should turn branch into an unconditional branch, which then
> > > > uses R_ARM_THM_JUMP24 relocation that has a range of 16MB.
> > >
> > > That would work too. Thumb 2 specific code would need to be guarded by
> > > #ifdef __thumb2__ though (which I think implies also renaming the file
> > > from .s to .S ?) and I'm not sure if the extra complexity justifies
> > > saving one instruction in the ARM case.
> >
> > I don't think it does. Also, current style is not to use "it" at all,
> > but rather -Wa,-mimplicit-it=always. I'm not sure if unified syntax
> > accepts "it" in arm mode when the following insn has a matching
> > condition suffix, but here it wouldn't I think...
> 
> Any issues with merging this now?

Looks fine. Applying. Sorry I overlooked this.

Rich


      reply	other threads:[~2019-12-07 18:03 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-18  6:04 Andre McCurdy
2019-09-18 14:28 ` Khem Raj
2019-09-18 17:52   ` Andre McCurdy
2019-09-18 19:54     ` Rich Felker
2019-11-21 20:54       ` Andre McCurdy
2019-12-07 18:03         ` Rich Felker [this message]

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