Re: [PATCH v2 1/3] lib/string: optimized memcpy

[Ben Dooks]

On 02/07/2021 13:31, Matteo Croce wrote:
> From: Matteo Croce <mcroce@xxxxxxxxxxxxx>
>
> Rewrite the generic memcpy() to copy a word at time, without generating
> unaligned accesses.
>
> The procedure is made of three steps:
> First copy data one byte at time until the destination buffer is aligned
> to a long boundary.
> Then copy the data one long at time shifting the current and the next long
> to compose a long at every cycle.
> Finally, copy the remainder one byte at time.
>
> This is the improvement on RISC-V:
>
> original aligned:	 75 Mb/s
> original unaligned:	 75 Mb/s
> new aligned:		114 Mb/s
> new unaligned:		107 Mb/s
>
> and this the binary size increase according to bloat-o-meter:
>
> Function     old     new   delta
> memcpy        36     324    +288
>
>
> Signed-off-by: Matteo Croce <mcroce@xxxxxxxxxxxxx>
> ---
>   lib/string.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 77 insertions(+), 3 deletions(-)

Doesn't arch/riscv/lib/memcpy.S also exist for an architecture
optimised version? I would have thought the lib/string.c version
was not being used?


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Ben Dooks				http://www.codethink.co.uk/
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