Hi! > -----Original Message----- > From: Richard Biener [mailto:richard.guent...@gmail.com] > Sent: Monday, March 23, 2020 11:25 PM > To: Yangfei (Felix) <felix.y...@huawei.com> > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [RFC] Should widening_mul should consider block frequency? > > On Mon, Mar 23, 2020 at 10:53 AM Yangfei (Felix) <felix.y...@huawei.com> > wrote: > > > > Hi, > > > > I created a bug for this issue: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94269 > > Looks like widening_mul phase may move multiply instruction from outside > the loop to inside the loop, merging with one add instruction inside the loop. > > This will increase the cost of the loop at least on aarch64 (4 cycles vs 1 > cycle). I think widening_mul should consider block frequency when doing such > a combination. > > I mean something like: > > As written in the PR I'd follow fma generation and restrict defs to the same > BB.
Thanks for the suggestion. That should be more consistent. Attached please find the adapted patch. Bootstrap and tested on both x86_64 and aarch64 Linux platform. gcc: +2020-03-24 Felix Yang <felix.y...@huawei.com> + + PR tree-optimization/94269 + * tree-ssa-math-opts.c (convert_plusminus_to_widen): Restrict this + operation to single basic block. gcc/testsuite: +2020-03-24 Felix Yang <felix.y...@huawei.com> + + PR tree-optimization/94269 + * gcc.dg/pr94269.c: New test. + Thanks, Felix
pr94269-v1.patch
Description: pr94269-v1.patch
