[Bug string/25131] memcpy perfomance problem with ARM 32 A9be due to high cache-misses

["helugang at huawei dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=25131

--- Comment #15 from helugang <helugang at huawei dot com> ---
(In reply to Adhemerval Zanella from comment #13)
> I forgot to mention that if compiler also targets armv7 with -mfpu=neon as
> default the ifunc selector won't be used and instead
> sysdeps/arm/armv7/multiarch/memcpy_neon.S will set as the default
> implementation.

Hi, Adhemerval
With --disable-multi-arch configured,default memcpy() in /sysdeps/arm/memcpy.S
works and the performance is worse than which __memcpy_vfp does.

(gdb) bt
#0  memcpy () at ../sysdeps/arm/memcpy.S:64
#1  0xb6e44e18 in __GI___mempcpy (dest=dest@entry=0xbefffb39,
        memcpy_vfp  vs memcpy in /sysdeps/arm/memcpy.S  
memcpy_1k_libmicro
        380.95153       449.6348
        380.96255       449.6283
        380.93659       449.6548
        380.95293       449.5687
        380.96071       449.6273
memcpy_800k_libmicro
        279131.15619    352820.5405
        286185.56789    353633.2598
        294103.06891    376391.7133
        285128.08039    389628.5461
        287601.79983    350731.9007
./memcpy_1m_libmicro
        460492.84609    527388.05897
        450131.39191    550715.5123
        443782.37169    536471.34533
        472516.11484    532723.39375
        494700.10173    537163.65616

I forgot to mention that if compiler also targets armv7 with -mfpu=neon as
default the ifunc selector won't be used and instead
sysdeps/arm/armv7/multiarch/memcpy_neon.S will set as the default
implementation.
>>About the __memcpy_neon ,it does’t work after -mfpu=neon is set,could you help to check whether  rebuilding glibc Is not enough to use  __memcpy_neon or __memcpy_arm.

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