Rob Herring <robherri...@gmail.com> writes:
> On 12/17/2010 03:27 PM, Måns Rullgård wrote:
>> Rob Herring<robherri...@gmail.com> writes:
>>
>>> From: Rob Herring<rob.herr...@calxeda.com>
>>>
>>> swab functions are heavily used by FDT code, so enable
>>> optimized assembly code for ARMv6 and later.
>>>
>>> Signed-off-by: Rob Herring<rob.herr...@calxeda.com>
>>> ---
>>> arch/arm/include/asm/byteorder.h | 16 ++++++++++++++++
>>> 1 files changed, 16 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/byteorder.h
>>> b/arch/arm/include/asm/byteorder.h
>>> index c3489f1..9df5844 100644
>>> --- a/arch/arm/include/asm/byteorder.h
>>> +++ b/arch/arm/include/asm/byteorder.h
>>> @@ -23,6 +23,22 @@
>>> # define __SWAB_64_THRU_32__
>>> #endif
>>>
>>> +#if defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_6__)
>>> +static inline __u16 __attribute__((const)) ___arch_swab16(__u16 x)
>>> +{
>>> + __asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x));
>>> + return x;
>>> +}
>>
>> Pay close attention to what gcc does with this as it is prone to add
>> unnecessary masking of the low halfword. If the callers are
>> well-behaved (argument having top halfword clear), making the
>> parameter and return types here plain unsigned (or u32) gives better
>> code.
>
> This straight from the Linux code and there are only a few users of
> swab16 (none in my build).
Look at the generated code if you don't believe me.
--
Måns Rullgård
m...@mansr.com
_______________________________________________
U-Boot mailing list
U-Boot@lists.denx.de
http://lists.denx.de/mailman/listinfo/u-boot
