[U-Boot] [PATCH 1/3] memcpy: use 32-bit copies if possible

[Wolfgang Denk]

Dear Joakim Tjernlund,

In message <OF26FEA2CB.36E102EE-ONC1257649.0031301D-C1257649.0031EDAF at transmode.se> you wrote:
>
> > How about:
> >
> >       cl = 0;
> >       for (i=0; i<sizeof(long); ++i) {
> >          cl <<= 8;
> >          cl |= c & 0xff;
> >       }
> >
> > GCC optimization will do the rest...
> 
> If you want gcc to optimise well, make it easy to do so.
> Changing the for loop into:
>       for (i=sizeof(long); i; --i)
> makes it easier for gcc and more likely to result in optimal code.

Did you actually _check_ the code? (I did).

It does not matter. The generated code is identical.

What matters might be compiler options - "-Os" generates a small loop,
and "-O3" and higher will unroll the loop, which is way more code.

Best regards,

Wolfgang Denk

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