From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Riesen <raa.lkml@gmail.com>
Subject: Re: [PATCH] Make strbuf_cmp inline, constify its arguments and optimize it a bit
Date: Sun, 7 Oct 2007 23:57:49 +0200
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References: <1190625904-22808-1-git-send-email-madcoder@debian.org> <1190625904-22808-2-git-send-email-madcoder@debian.org> <20071007140052.GA3260@steel.home> <85fy0nknnq.fsf@lola.goethe.zz> <20071007161012.GB3270@steel.home> <851wc6lwkc.fsf@lola.goethe.zz>
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To: David Kastrup <dak@gnu.org>
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David Kastrup, Sun, Oct 07, 2007 18:27:15 +0200:
> Alex Riesen <raa.lkml@gmail.com> writes:
> >> > +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?
> 
> No, since the call to memcmp might change a->len or b->len.  A

Huh?! How's that? It is not even given them!