From: Nathan_Lynch@mentor.com (Nathan Lynch)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: disable GCC SRA optimization
Date: Wed, 2 Sep 2015 16:17:24 -0500 [thread overview]
Message-ID: <55E76764.2020200@mentor.com> (raw)
In-Reply-To: <CAKv+Gu_eOQ=ZACn1jzQU-z2ZMqX3PdUx9j05fXuGjniccS2x8Q@mail.gmail.com>
On 09/02/2015 11:45 AM, Ard Biesheuvel wrote:
> On 2 September 2015 at 18:28, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>> This is a known but as yet unresolved issue.
>> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65932). In this particular
>> case, it is causing the second while loop to be executed erroneously a
>> single time, causing the additional space characters to be printed.
>>
>> So disable the optimization by passing -fno-ipa-sra.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>
>> Needs to go to stable perhaps?
>> The emitted asm is at the end of this patch.
>>
>
> Another report of the same issue:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66271
Comments in both bugs indicate that this happens only when building with
-Os and not -O2. Have you (or anyone else) been able to get bad code
with -O2?
I don't think the answer should affect the patch itself, but it might be
kind to note in the commit message whether -Os definitely makes the
difference here, if this information is known.
next prev parent reply other threads:[~2015-09-02 21:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-02 16:28 [PATCH] ARM: disable GCC SRA optimization Ard Biesheuvel
2015-09-02 16:45 ` Ard Biesheuvel
2015-09-02 21:17 ` Nathan Lynch [this message]
2015-09-03 6:45 ` Ard Biesheuvel
2015-09-02 19:37 ` Nicolas Pitre
2015-09-03 14:20 ` Ard Biesheuvel
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