From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Tue, 11 Jan 2011 18:53:06 +0000 Subject: [PATCH] bitops: remove condition code clobber for CLZ In-Reply-To: References: <1294767725-14814-1-git-send-email-rabin@rab.in> <20110111183942.GL11039@n2100.arm.linux.org.uk> Message-ID: <20110111185306.GM11039@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 11, 2011 at 01:51:19PM -0500, Nicolas Pitre wrote: > On Tue, 11 Jan 2011, Russell King - ARM Linux wrote: > > > On Tue, Jan 11, 2011 at 11:12:05PM +0530, Rabin Vincent wrote: > > > The CLZ instruction does not alter the condition flags, so remove the > > > "cc" clobber from the inline asm for fls(). > > > > Do you have any evidence that this changes anything, or is it just > > subjective? > > This probably doesn't change anything, as gcc has been presuming that > inline asms do clobber the condition code for years now, in order to > prevent issues caused by a lack of %? appended to instructions in order > to conditionally execute them otherwise. So this would only make the > code self consistent. So given that Linus complains about churn from ARM, what's the justification to apply a patch which has no effect what so ever?