David Kastrup, Sun, Oct 07, 2007 16:24:57 +0200:
> Alex Riesen <raa.lkml@xxxxxxxxx> writes:
>
> > It is definitely less code (also object code). It is not always
> > measurably faster (but mostly is).
>
> > -int strbuf_cmp(struct strbuf *a, struct strbuf *b)
> > -{
> > - int cmp;
> > - if (a->len < b->len) {
> > - cmp = memcmp(a->buf, b->buf, a->len);
> > - return cmp ? cmp : -1;
> > - } else {
> > - cmp = memcmp(a->buf, b->buf, b->len);
> > - return cmp ? cmp : a->len != b->len;
> > - }
> > -}
> > -
>
> > +static inline int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
> > +{
> > + int len = a->len < b->len ? a->len: b->len;
> > + int cmp = memcmp(a->buf, b->buf, len);
> > + if (cmp)
> > + return cmp;
> > + return a->len < b->len ? -1: a->len != b->len;
> > +}
>
> My guess is that you are conflating two issues about speed here: the
> inlining will like speed the stuff up. But having to evaluate the
> (a->len < b->len) comparison twice will likely slow it down.
Can't the result of the expression be reused in compiled?
Isn't it a common expression?
> So if you do any profiling, you should do it on both separate angles
> of this patch.
>
I compared the inlined versions of both.
-
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