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From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Regression due to 0c44c2d0f459 x86: Use asm goto to implement better modify_and_test() functions
Date: Wed, 4 Dec 2013 09:59:53 +0100	[thread overview]
Message-ID: <20131204085953.GC31778@gmail.com> (raw)
In-Reply-To: <529E8719.4070202@zytor.com>


* H. Peter Anvin <hpa@zytor.com> wrote:

> Hi guys,
> 
> 0c44c2d0f459 x86: Use asm goto to implement better modify_and_test()
> functions
> 
> causes a regression, because it incorrectly changed the constraints of
> bitops.
> 
> Specifically, the GEN_BINARY_RMWcc() hardcodes a constraint as "er", but
> it needs to be "Ir" for the bitops themselves.  "I" is correct (as
> opposed to "J" even on 64 bits, because we only generate the 64-bit
> version when we have a register operand.
> 
> Unfortunately there isn't a way we can get gcc+gas to generate a version
> with an offset pointer.

Does the regression manifest itself in any actual breakage - if yes, 
how does it look like? (People experiencing similar symptoms will be 
helped by seeing a fix matching their problems.)

Thanks,

	ngo

  reply	other threads:[~2013-12-04  9:00 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-04  1:36 Regression due to 0c44c2d0f459 x86: Use asm goto to implement better modify_and_test() functions H. Peter Anvin
2013-12-04  8:59 ` Ingo Molnar [this message]
2013-12-04 16:44   ` H. Peter Anvin
2014-01-31 21:32     ` Alex Williamson
2013-12-04 22:51 ` [tip:x86/urgent] x86, bitops: Correct the assembly constraints to testing bitops tip-bot for H. Peter Anvin

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