On Fri, Apr 20, 2012 at 9:52 AM, Bin.Cheng <amker.ch...@gmail.com> wrote: > On Wed, Apr 18, 2012 at 5:25 PM, Richard Guenther > <richard.guent...@gmail.com> wrote: >> On Wed, Apr 18, 2012 at 8:53 AM, Bin.Cheng <amker.ch...@gmail.com> wrote: > >> >> I don't understand method 2. I'd do >> >> start at the single predecessor of the sink-to block >> >> foreach stmt from the end to the beginning of that block >> if the stmt has a VDEF or the same VUSE as the stmt we sink, break >> >> (continue searching for VDEFs in predecessors - that now gets more >> expensive, >> I suppose limiting sinking to the cases where the above finds sth >> would be easiest, >> even limiting sinking to never sink across any stores) >> >> walk the vuse -> vdef chain, using refs_anti_dependent_p to see whether >> the load is clobbered. >> >> But I'd suggest limiting the sinking to never sink across stores - the alias >> memory model we have in GCC seriously limits these anyway. How would >> the numbers change if you do that? > Interesting, maybe method 1 I implemented is too conservative. > I implemented as you described, and the numbers are: > 1) 766, If the stop condition is "stmt_may_clobber_ref_p" > 2) 719, if the stop condition is "gimple_vdef || stmt_may_clobber_ref_p" > > Also, I past make check on x86 for 1). > > Is it good? I am not sure about it since bootstrapping builds gcc 2 > times and libraries 3 times.
For 2) it is enough to test for gimple_vdef. I think that's the most reasonable approach - we can improve on it once we see that doing so would improve things for a testcase. Richard. > Thanks > -- > Best Regards.
