Eric Dumazet <dada1@xxxxxxxxxxxxx> writes:
> While doing oprofile tests I noticed two loops are not properly unrolled by gcc
That's because nobody passed -funroll-loops. Did you try that for
that file? Likely will need -O2 too
> +static unsigned long ifname_compare(const void *_a, const void *_b, const void *_mask)
> +{
> + const unsigned long *a = (const unsigned long *)_a;
> + const unsigned long *b = (const unsigned long *)_b;
> + const unsigned long *mask = (const unsigned long *)_mask;
> + unsigned long ret;
> +
> + ret = (a[0] ^ b[0]) & mask[0];
> + ret |= (a[1] ^ b[1]) & mask[1];
> + if (IFNAMSIZ > 2 * sizeof(unsigned long))
> + ret |= (a[2] ^ b[2]) & mask[2];
> + if (IFNAMSIZ > 3 * sizeof(unsigned long))
> + ret |= (a[3] ^ b[3]) & mask[3];
That will silently break for IFNAMSIZ >= 4*sizeof(unsigned long)
You should add a dummy loop for that or at least a BUILD_BUG_ON
-Andi
--
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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