> Some targets have -mbranch-cost to allow overriding the default costing.
> visium has a branch cost of 10!
Yeah, the GR5 variant is pipelined but has no branch prediction; moreover
there is an additional adverse effect coming for the instructions bus...
> Several ports have a cost of 6
On Fri, Sep 11, 2015 at 10:04:12AM +0100, Ramana Radhakrishnan wrote:
> On Fri, Sep 11, 2015 at 10:53:13AM +0200, Bernd Schmidt wrote:
> > On 09/10/2015 11:11 PM, Jeff Law wrote:
> > >I think that's probably what James is most interested in getting some
> > >ideas around -- the cost model.
> > >
>
On 10/09/15 22:11, Jeff Law wrote:
On 09/10/2015 12:23 PM, Bernd Schmidt wrote:
> No testcase provided, as currently I don't know of targets with a high
> enough branch cost to actually trigger the optimisation.
Hmm, so the code would not actually be used right now? In that case I'll
On 09/10/2015 11:11 PM, Jeff Law wrote:
I think that's probably what James is most interested in getting some
ideas around -- the cost model.
I think the fundamental problem is BRANCH_COST isn't actually relative
to anything other than the default value of "1". It doesn't directly
correspond
On Fri, Sep 11, 2015 at 10:53:13AM +0200, Bernd Schmidt wrote:
> On 09/10/2015 11:11 PM, Jeff Law wrote:
> >I think that's probably what James is most interested in getting some
> >ideas around -- the cost model.
> >
> >I think the fundamental problem is BRANCH_COST isn't actually relative
> >to
On 09/11/2015 02:49 AM, Kyrill Tkachov wrote:
On 10/09/15 22:11, Jeff Law wrote:
On 09/10/2015 12:23 PM, Bernd Schmidt wrote:
> No testcase provided, as currently I don't know of targets with a
high
> enough branch cost to actually trigger the optimisation.
Hmm, so the code would not
On 09/08/2015 04:53 PM, James Greenhalgh wrote:
One big question I have with this patch is how I ought to write a meaningful
cost model I've used. It seems like yet another misuse of RTX costs, and
another bit of stuff for targets to carefully balance. Now, if the
relative cost of branches and
On 09/10/2015 12:23 PM, Bernd Schmidt wrote:
> No testcase provided, as currently I don't know of targets with a high
> enough branch cost to actually trigger the optimisation.
Hmm, so the code would not actually be used right now? In that case I'll
leave it to others to decide whether we
Hi,
RTL "noce" ifcvt will currently give up if the branches it is trying to
make conditional are too complicated. One of the conditions for "too
complicated" is that the branch sets more than one value.
One common idiom that this misses is something like:
int d = a[i];
int e = b[i];
if
