From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: no-op delay loops
Organization: D03
Date: Fri, 27 Nov 2015 09:53:50 +0100
Message-ID: <87si3rbz6p.fsf@rasmusvillemoes.dk>
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Hi,

It seems that gcc happily compiles

for (i = 0; i < 1000000000; ++i) ;

into simply

i = 1000000000;

(which is then usually eliminated as a dead store). At least at -O2, and
when i is not declared volatile. So it would seem that the loops at

arch/mips/pci/pci-rt2880.c:235
arch/mips/pmcs-msp71xx/msp_setup.c:80
arch/mips/sni/reset.c:35

actually don't do anything. (In the middle one, i is 'register', but
that doesn't change anything.) Is mips compiled with some special flags
that would make gcc actually emit code for the above?

Rasmus
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