https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94043
--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> --- On Fri, 20 Mar 2020, linkw at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94043 > > --- Comment #4 from Kewen Lin <linkw at gcc dot gnu.org> --- > This was just exposed from my commit, it can also be reproduced without my > commit but with -fno-vect-cost-model. > > Some loops we have for this case: > ;; Loop 1 > ;; header 3, latch 10 > ;; depth 1, outer 0 > ;; nodes: 3 10 8 23 25 34 35 26 29 32 33 38 4 11 37 31 > > ;; Loop 2 > ;; header 4, latch 11 > ;; depth 2, outer 1 > ;; nodes: 4 11 > > ;; Loop 4 > ;; header 26, latch 29 > ;; depth 2, outer 1 > ;; nodes: 26 29 > > > When we are doing versioning for loop4 required for aliasing check, the > related > scalar_loop_iters is based on e2.2_31, which is defined in BB 4, that is: > > <bb 4> [local count: 4343773762]: > # e2.2_31 = PHI <_15(11), 1(37)> > # ivtmp_14 = PHI <ivtmp_23(11), 4(37)> > > > For the codes: > > if ((def_bb = gimple_bb (SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p)))) > && flow_bb_inside_loop_p (outermost, def_bb)) > outermost = superloop_at_depth (loop, bb_loop_depth (def_bb) + 1) > > bb_loop_depth is 2, the +1 make the assertion in superloop_at_depth fail since > the current loop 4 only has the depth 2. I think the existing code has the > assumption that all operands in stmts of cond_expr_stmt_list are defined in > some outer loop of current, but the assumption breaks in this case. > > I guess the current scalar_loop_iters is valid? Then the fix can be: What is not valid I think is that e2.2_31 should have a loop-closed PHI node which would place it in an outer loop. You'd have to see why either the loop-closed PHI is not present or why the aliasing check doesn't use that (it's more likely this) > --- a/gcc/tree-vect-loop-manip.c > +++ b/gcc/tree-vect-loop-manip.c > @@ -3312,7 +3312,13 @@ vect_loop_versioning (loop_vec_info loop_vinfo, > FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) > if ((def_bb = gimple_bb (SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p)))) > && flow_bb_inside_loop_p (outermost, def_bb)) > - outermost = superloop_at_depth (loop, loop_depth (outermost) + 1); > + { > + /* Def block can be in either one outer loop of loop_to_version or > + one sibling of outer loop of loop_to_version. */ > + class loop *common_loop > + = find_common_loop (def_bb->loop_father, loop); > + outermost = superloop_at_depth (loop, loop_depth (common_loop) + > 1); > + } > } > >
