From: Arnd Bergmann <arnd@arndb.de>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: "open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
<linux-crypto@vger.kernel.org>,
kbuild test robot <fengguang.wu@intel.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [cryptodev:master 130/134] aes_generic.c:undefined reference to `_restgpr_31_x'
Date: Sun, 14 Jan 2018 22:40:36 +0100 [thread overview]
Message-ID: <CAK8P3a30k-JjMJ0M9KWXqUMT3eHmuuFvAe1KuKdqNoAiSZrgog@mail.gmail.com> (raw)
In-Reply-To: <20180112221050.GR21977@gate.crashing.org>
On Fri, Jan 12, 2018 at 11:10 PM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> On Fri, Jan 12, 2018 at 10:45:31PM +0100, Arnd Bergmann wrote:
>> > I guess you could enable the _x routines whenever you use ubsan? Ubsan
>> > will cause much bigger code growth than the handful of insns in those
>> > routines?
>>
>> Right, that could work, too. My patch that Herbert merged intentionally
>> used -Os also for non-UBSAN builds because it turned out to
>> be much faster (see gcc PR83651),
>
> "Much"?
>
> -Os is *slower* with 8.0, 5% faster with 7.2, 4% faster with 7.1,
> slower with 7.0 and 6.3. Your numbers, #c1.
>
> Anf this is the generic code of course, which is slow anyway (not to
> mention insecure).
Right. I've done some more investigation anyway, starting over with the
analysis of the gcc options that change it. I've found now that turning
off '-fcode-hoisting' but leaving on the other options I had suspected
earlier (-O2 instead of -Os, -ftree-sra, -ftree-pre) also fixes the
stack problem, and appears to result in the best performance so
far. I need to rerun the whole test matrix, but that seems rather
promising, and the result may also help debug what's really happening.
Arnd
next prev parent reply other threads:[~2018-01-14 21:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 14:11 [cryptodev:master 130/134] aes_generic.c:undefined reference to `_restgpr_31_x' kbuild test robot
2018-01-12 14:55 ` Arnd Bergmann
2018-01-12 16:39 ` Segher Boessenkool
2018-01-12 19:43 ` Arnd Bergmann
2018-01-12 20:41 ` Segher Boessenkool
2018-01-12 21:29 ` Arnd Bergmann
2018-01-12 21:41 ` Segher Boessenkool
2018-01-12 21:45 ` Arnd Bergmann
2018-01-12 22:10 ` Segher Boessenkool
2018-01-14 21:40 ` Arnd Bergmann [this message]
2018-01-15 0:21 ` Segher Boessenkool
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