On Fri, Apr 20, 2012 at 4:54 PM, Richard Guenther <richard.guent...@gmail.com> wrote: > 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. I am a little confused. does not "gimple_code (stmt) == GIMPLE_ASM"/"call_may_clobber_ref_p_1 (stmt, ref)" matter? These are checked by stmt_may_clobber_ref_p.
Thanks. -- Best Regards.
