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

[Simon Horman <horms@xxxxxxxxxxxx>]

On Tue, Jul 01, 2014 at 04:58:24PM +0100, 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@xxxxxxxxxxxxxxxx>

A conflict in next notification from Stephen Rothwell tells me that this
has made it there but regardless I would like to note that I have
successfully tested this on the following shmobile boards:
Genmai, Koelsh, Lager, Marzen, Bockw, APE6EVM, KZM9D, KZM9G,
Armadillo800 EVA and Mackerel. This covers all but one board (I do not
have access to a Henninger) and all SoCs supported in mainline.

Accordingly, the shmobile portion:

Tested-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>


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