linux-kernel - Regression due to 0c44c2d0f459 x86: Use asm goto to implement better modify_and

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Message-ID: <529E8719.4070202@zytor.com>
Date:	Tue, 03 Dec 2013 17:36:25 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Regression due to 0c44c2d0f459 x86: Use asm goto to implement better
 modify_and_test() functions

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.

	-hpa

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