On Wed, Jun 28, 2017 at 8:06 PM, Richard Sandiford <richard.sandif...@linaro.org> wrote: > "Bin.Cheng" <amker.ch...@gmail.com> writes: >> On Wed, Jun 28, 2017 at 5:56 PM, Richard Sandiford >> <richard.sandif...@linaro.org> wrote: >>> "Bin.Cheng" <amker.ch...@gmail.com> writes: >>>> Question is what would happen if simple_iv succeeds with non-ZERO step >>>> when called with nest==NULL? The patch skips simple_iv and forces >>>> ZERO step? >>> >>> Yeah, I mentioned that in the covering note: >>> >>> The handling seemed strange though. If the DR was part of a loop, >>> we still tried to express the base and offset values as IVs, potentially >>> giving a nonzero step. If that failed for any reason, we'd revert to >>> using the original base and offset, just as we would if we hadn't asked >>> for an IV in the first place. >> Hmm, it says "If that failed for any reason, .... revert to using the >> original base and offset, just as we would if we hadn't asked for an >> IV in the first place", but question is what would happen if simple_iv >> succeeds with nest==NULL. After change, the successful simple_iv is >> bypassed. It's likely this case can't happen in reality. > > I suspect we're really in violent agreement here :-) but the reason > I was surprised at the question was that you seemed to be treating > the nest==NULL && simple_iv/nonzero-step combination as a corner case > that hadn't really been addressed, whereas removing that combination is > the main point of the patch. The reason for removing it isn't that it Yes, this is where I misunderstood the patch. Thanks very much for your patient explanation. Now I can see it IS a nice simplification.
Thanks, Bin > can't happen (bb-slp-pr65935.c proves that it did, to detrimental effect). > The reason is that IMO it isn't useful. I don't think it makes sense to > set the step to a nonzero value for "BB analysis". > > Thanks, > Richard
