From: Peter Zijlstra <peterz@infradead.org>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Richard Henderson <rth@redhat.com>,
Vladimir Makarov <vmakarov@redhat.com>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH] x86: Optimize variable_test_bit()
Date: Fri, 1 May 2015 18:46:40 +0200 [thread overview]
Message-ID: <20150501164639.GA19158@dyad.arnhem.chello.nl> (raw)
In-Reply-To: <20150501163329.GU1751@tucnak.redhat.com>
On Fri, May 01, 2015 at 06:33:29PM +0200, Jakub Jelinek wrote:
> On Fri, May 01, 2015 at 09:03:32AM -0700, Linus Torvalds wrote:
> > > PPS. Jakub, I see gcc5.1 still hasn't got output operands for asm goto;
> > > is this something we can get 'fixed' ?
>
> CCing Richard as author of asm goto and Vlad as register allocator
> maintainer. There are a few enhancement requests to support this, like
> http://gcc.gnu.org/PR59615 and http://gcc.gnu.org/PR52381 , but indeed the
> reason why no outputs are allowed is the register allocation issue.
> Don't know if LRA would be better suited to handle that case, but it would
> indeed be pretty hard.
So it would b awesome if we could use these freshly modeled flags as output
for regular asm stmts; that would obviate much of the asm goto hackery we now
do/have and allow gcc to pick the right branch for likely/unlikely.
next prev parent reply other threads:[~2015-05-01 16:56 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-01 15:16 [PATCH] x86: Optimize variable_test_bit() Peter Zijlstra
2015-05-01 16:03 ` Linus Torvalds
2015-05-01 16:16 ` Peter Zijlstra
2015-05-01 16:29 ` Peter Zijlstra
2015-05-01 16:18 ` Peter Zijlstra
2015-05-01 16:33 ` Jakub Jelinek
2015-05-01 16:45 ` Linus Torvalds
2015-05-01 16:46 ` Peter Zijlstra [this message]
2015-05-01 17:17 ` Ingo Molnar
2015-05-01 19:02 ` Vladimir Makarov
2015-05-01 20:49 ` Linus Torvalds
2015-05-01 22:22 ` Vladimir Makarov
2015-05-02 12:39 ` Peter Zijlstra
2015-05-04 15:37 ` Richard Henderson
2015-05-04 19:33 ` [RFC] Design for flag bit outputs from asms Richard Henderson
2015-05-04 20:14 ` H. Peter Anvin
2015-05-04 20:27 ` H. Peter Anvin
2015-05-04 20:33 ` Richard Henderson
2015-05-04 20:45 ` Linus Torvalds
2015-05-04 20:57 ` Richard Henderson
2015-05-04 21:23 ` H. Peter Anvin
2015-05-04 20:35 ` Linus Torvalds
2015-05-04 20:42 ` H. Peter Anvin
2015-05-05 9:01 ` Gabriel Paubert
2015-05-05 13:50 ` Segher Boessenkool
2015-05-05 15:37 ` Linus Torvalds
2015-05-05 16:10 ` Segher Boessenkool
2015-05-02 12:43 ` [PATCH] x86: Optimize variable_test_bit() Peter Zijlstra
2015-05-04 18:07 ` Vladimir Makarov
2015-05-04 20:14 ` H. Peter Anvin
2015-05-04 13:42 ` Peter Zijlstra
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