On Tue, 19 Jun 2012, William J. Schmidt wrote: > On Tue, 2012-06-19 at 12:10 +0200, Richard Guenther wrote: > > On Mon, 18 Jun 2012, William J. Schmidt wrote: > > > > > On Mon, 2012-06-18 at 13:49 -0500, William J. Schmidt wrote: > > > > On Mon, 2012-06-11 at 13:40 +0200, Richard Guenther wrote: > > > > > On Fri, 8 Jun 2012, William J. Schmidt wrote: > > > > > > > > > <snip> > > > > > > > > > > Hmm. I don't like this patch or its general idea too much. Instead > > > > > I'd like us to move more of the cost model detail to the target, > > > > > giving > > > > > it a chance to look at the whole loop before deciding on a cost. ISTR > > > > > posting the overall idea at some point, but let me repeat it here > > > > > instead > > > > > of trying to find that e-mail. > > > > > > > > > > The basic interface of the cost model should be, in targetm.vectorize > > > > > > > > > > /* Tell the target to start cost analysis of a loop or a basic-block > > > > > (if the loop argument is NULL). Returns an opaque pointer to > > > > > target-private data. */ > > > > > void *init_cost (struct loop *loop); > > > > > > > > > > /* Add cost for N vectorized-stmt-kind statements in vector_mode. > > > > > */ > > > > > void add_stmt_cost (void *data, unsigned n, > > > > > vectorized-stmt-kind, > > > > > enum machine_mode vector_mode); > > > > > > > > > > /* Tell the target to compute and return the cost of the accumulated > > > > > statements and free any target-private data. */ > > > > > unsigned finish_cost (void *data); > > > > > > By the way, I don't see much point in passing the void *data around > > > here. Too many levels of interfaces that we'd have to pass it around in > > > the vectorizer, so it would just sit in a static variable. Might as > > > well let the data be wholly private to the target. > > > > Ok, so you'd have void init_cost (struct loop *) and > > unsigned finish_cost (void); then? Static variables are of couse > > not properly "abstracted" so we can't ever compute two set of costs > > at the same time ... but that's true all-over-the-place in GCC ... > > It's a fair point, and perhaps I'll decide to pass the data pointer > around anyway to keep that option open. We'll see which looks uglier. > > > > > With previous discussion the add_stmt_cost hook would be split up > > to also allow passing the operation code for example. > > I remember having this discussion, and I was looking for it to check on > the details, but I can't seem to find it either in my inbox or in the > archives. Can you please point me to that again? Sorry for the bother.
It was in the "Correct cost model for strided loads" thread. Richard.
