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From: Philipp Tomsich <philipp.tomsich@vrull.eu>
Date: Wed, 16 Nov 2022 01:36:22 +0100
Message-ID: <CAAeLtUAOAkiZkTtbww=NxFQRxe_g9M_QATy6Aker1RBP8thi-Q@mail.gmail.com>
Subject: Re: [PATCH] RISC-V: Use .p2align for code-alignment
To: Jeff Law <jeffreyalaw@gmail.com>
Cc: gcc-patches@gcc.gnu.org, Christoph Muellner <christoph.muellner@vrull.eu>, 
	Palmer Dabbelt <palmer@rivosinc.com>, Vineet Gupta <vineetg@rivosinc.com>, 
	Kito Cheng <kito.cheng@gmail.com>, Jeff Law <jlaw@ventanamicro.com>
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On Tue, 15 Nov 2022 at 22:14, Philipp Tomsich <philipp.tomsich@vrull.eu> wr=
ote:
>
> Jeff,
>
> On Tue, 15 Nov 2022 at 17:37, Jeff Law <jeffreyalaw@gmail.com> wrote:
> >
> >
> > On 11/13/22 13:41, Philipp Tomsich wrote:
> >
> > RISC-V's .p2align (currently) ignores the max-skip argument.  As we
> > have experimental patches underway to address this in a
> > backwards-compatible manner, let's prepare GCC for the day when
> > binutils gets updated.
> >
> > gcc/ChangeLog:
> >
> > * config/riscv/riscv.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Implement.
> >
> >
> > What are the implications if we start using p2align immediately when th=
e current (broken?) state of the assembler?  I'm pretty sure configure is a=
lready turning on HAVE_GAS_SKIP_P2ALIGN.  From a native risc-v build:
> >
> >
> > auto-host.h:#define HAVE_GAS_MAX_SKIP_P2ALIGN 1
>
> This is your tree, which has the (partial fix =E2=80=94 i.e., the best we=
 can
> do without breaking backward compatibility) for .p2align.
> When building against upstream binutils, this should not be defined.

After rereading the generated configure-script, I've changed my mind
The check the does nothing to ensure that the max-skip is actually
honored and only tests whether it is accepted.

Having the max-skip silently ignored may still be the lesser evil.

Philipp.