From: Tomasz Figa <tomasz.figa@gmail.com>
Subject: Re: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+
 (part1)
Date: Sat, 05 Jul 2014 03:06:39 +0200
Message-ID: <53B74F9F.8030604@gmail.com>
References: <E1X20mL-00083I-Sv@rmk-PC.arm.linux.org.uk>
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To: Russell King <rmk+kernel@arm.linux.org.uk>,
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Hi Russell,

On 01.07.2014 18:19, Russell King wrote:
> ARMv6 and greater introduced a new instruction ("bx") which can be used
> to return from function calls.  Recent CPUs perform better when the
> "bx lr" instruction is used rather than the "mov pc, lr" instruction,
> and this sequence is strongly recommended to be used by the ARM
> architecture manual (section A.4.1.1).
> 
> We provide a new macro "ret" with all its variants for the condition
> code which will resolve to the appropriate instruction.
> 
> Rather than doing this piecemeal, and miss some instances, change all
> the "mov pc" instances to use the new macro, with the exception of
> the "movs" instruction and the kprobes code.  This allows us to detect
> the "mov pc, lr" case and fix it up - and also gives us the possibility
> of deploying this for other registers depending on the CPU selection.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Build- and boot-tested on mach-s3c64xx.

Tested-by: Tomasz Figa <tomasz.figa@gmail.com>

Best regards,
Tomasz