On Fri, 15 Nov 2024, Alex Coplan wrote: > On 29/10/2024 13:41, Richard Biener wrote: > > On Mon, 28 Oct 2024, Alex Coplan wrote: > > > > > From: Tamar Christina <tamar.christ...@arm.com> > > > > > > The alignment peeling changes exposed a latent missing dominator update > > > with early break vectorization, specifically when inserting the vector > > > skip edge, since the new edge bypasses the prolog skip block and thus > > > has the potential to subvert its dominance. This patch fixes that. > > > > OK. > > Thanks. Regular (-O2) bootstrap on aarch64-linux-gnu showed this > triggers -Wmaybe-uninitialized due to the new use of the prolog variable > (which I think is a false positive, since it's guarded by > prolog_peeling). The attached version works around it by initializing > prolog to NULL. Incrementally, that's: > > diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc > index 1dcb0b427f0..f98c162fc0a 100644 > --- a/gcc/tree-vect-loop-manip.cc > +++ b/gcc/tree-vect-loop-manip.cc > @@ -3198,7 +3198,7 @@ vect_do_peeling (loop_vec_info loop_vinfo, tree niters, > tree nitersm1, > prob_prolog = prob_epilog = profile_probability::guessed_always () > .apply_scale (estimated_vf - 1, estimated_vf); > > - class loop *prolog, *epilog = NULL; > + class loop *prolog = NULL, *epilog = NULL; > class loop *first_loop = loop; > bool irred_flag = loop_preheader_edge (loop)->flags & > EDGE_IRREDUCIBLE_LOOP; > > I guess the incremental change should be obvious, but just to check you're > happy > with the workaround, is the updated version OK?
Sure. > Alex > > > > > Thanks, > > Richard. > > > > > gcc/ChangeLog: > > > > > > * tree-vect-loop-manip.cc (vect_do_peeling): Update immediate > > > dominators of nodes that were dominated by the prolog skip block > > > after inserting vector skip edge. > > > > > > gcc/testsuite/ChangeLog: > > > > > > * g++.dg/vect/vect-early-break_6.cc: New test. > > > > > > Co-Authored-By: Alex Coplan <alex.cop...@arm.com> > > > --- > > > .../g++.dg/vect/vect-early-break_6.cc | 25 +++++++++++++++++++ > > > gcc/tree-vect-loop-manip.cc | 24 ++++++++++++++++++ > > > 2 files changed, 49 insertions(+) > > > create mode 100644 gcc/testsuite/g++.dg/vect/vect-early-break_6.cc > > > > > > > > > > -- > > Richard Biener <rguent...@suse.de> > > SUSE Software Solutions Germany GmbH, > > Frankenstrasse 146, 90461 Nuernberg, Germany; > > GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg) > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
