Re: [Xen-devel] [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ (part1)

[Stephen Warren <swarren@xxxxxxxxxxxxx>]

On 07/01/2014 10:19 AM, 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.

Tested-by: Stephen Warren <swarren@xxxxxxxxxx>

(On an NVIDIA Tegra Jetson TK1 board, both CPU hotplug and system sleep
were tested, which are the use-cases that actually use the edited
assembly files)

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