From: Ard Biesheuvel <ardb@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>, Peter.Smith@arm.com
Cc: Stefan Agner <stefan@agner.ch>, Tony Lindgren <tony@atomide.com>,
Russell King <linux@armlinux.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
linux-omap@vger.kernel.org,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] ARM: OMAP2+: drop unnecessary adrl
Date: Thu, 2 Apr 2020 11:48:19 +0200 [thread overview]
Message-ID: <CAMj1kXGYiMobkue642iDRdOjEHQK=KXpp=Urrgik9UU-eWWibQ@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdkyOW6RXTOCt1xMp2H+uH28ofByQOjyx776t8RDxTED2w@mail.gmail.com>
On Wed, 1 Apr 2020 at 20:02, Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Sun, Mar 29, 2020 at 1:33 PM Stefan Agner <stefan@agner.ch> wrote:
> >
> > The adrl instruction has been introduced with commit dd31394779aa ("ARM:
> > omap3: Thumb-2 compatibility for sleep34xx.S"), back when this assembly
> > file was considerably longer. Today adr seems to have enough reach, even
> > when inserting about 60 instructions between the use site and the label.
> > Replace adrl with conventional adr instruction.
> >
> > This allows to build this file using Clang's integrated assembler (which
> > does not support the adrl pseudo instruction).
>
> Context: https://github.com/ClangBuiltLinux/linux/issues/430#issuecomment-476124724
> If Peter says it's difficult to implement, I trust him.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
I take it this implies that the LLVM linker does not support the
R_ARM_ALU_PC_Gn relocations? Since otherwise, adrl could simply be
expanded to a pair of adds with the appropriate relocations, letting
the linker fix up the immediates (and the ADD vs SUB bits)
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/430
> > Signed-off-by: Stefan Agner <stefan@agner.ch>
> > ---
> > arch/arm/mach-omap2/sleep34xx.S | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-omap2/sleep34xx.S
> > index ac1324c6453b..c4e97d35c310 100644
> > --- a/arch/arm/mach-omap2/sleep34xx.S
> > +++ b/arch/arm/mach-omap2/sleep34xx.S
> > @@ -72,7 +72,7 @@ ENTRY(enable_omap3630_toggle_l2_on_restore)
> > stmfd sp!, {lr} @ save registers on stack
> > /* Setup so that we will disable and enable l2 */
> > mov r1, #0x1
> > - adrl r3, l2dis_3630_offset @ may be too distant for plain adr
> > + adr r3, l2dis_3630_offset
> > ldr r2, [r3] @ value for offset
> > str r1, [r2, r3] @ write to l2dis_3630
> > ldmfd sp!, {pc} @ restore regs and return
> > --
> > 2.25.1
> >
> > --
> > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/5a6807f19fd69f2de6622c794639cc5d70b9563a.1585513949.git.stefan%40agner.ch.
>
>
>
> --
> Thanks,
> ~Nick Desaulniers
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-04-02 9:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-29 20:33 [PATCH] ARM: OMAP2+: drop unnecessary adrl Stefan Agner
2020-04-01 18:02 ` Nick Desaulniers
2020-04-02 9:48 ` Ard Biesheuvel [this message]
2020-04-02 11:50 ` Peter Smith
2020-04-02 12:05 ` Ard Biesheuvel
2020-04-02 14:34 ` Stefan Agner
2020-04-02 14:36 ` Ard Biesheuvel
2020-04-17 15:23 ` Tony Lindgren
2020-04-02 17:50 ` Peter Smith
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