On Tue, 1 Feb 2022, Jakub Jelinek wrote:
> On Tue, Feb 01, 2022 at 10:29:03AM +0100, Richard Biener wrote:
> > So I think it's all fine besides the handling of VEC_COND_EXPRs where
> > the use is in rhs1 and rhs2 and/or rhs3 - I don't really understand
> > your worry here but shouldn't the stmt end up on the vector at least
> > once? You can use gimple_assign_rhs1_ptr to see whether the
>
> My worry is that
> FOR_EACH_IMM_USE_FAST (use_p, iterator, lhs)
> uses.safe_push (USE_STMT (use_p));
> for a stmt with multiple uses of lhs pushes the same
> stmt multiple times.
> And then
> if (a_is_comparison)
> a = gimplify_build2 (gsi, code, type, a1, a2);
> a1 = gimplify_build2 (gsi, BIT_AND_EXPR, type, a, b);
> a2 = gimplify_build1 (gsi, BIT_NOT_EXPR, type, a);
> a2 = gimplify_build2 (gsi, BIT_AND_EXPR, type, a2, c);
> a = gimplify_build2 (gsi, BIT_IOR_EXPR, type, a1, a2);
> gimple_assign_set_rhs_from_tree (gsi, a);
> update_stmt (gsi_stmt (*gsi));
> will modify it (though the above at least will not remove the
> stmt and update it in place I think) and then it won't be
> a VEC_COND_EXPR anymore.
Ah, OK. Sure, pushing the stmt multiple times looks bogus and indeed
if we see we'll visit it a second time for a rhs{2,3} use there's
no point in pushing it in the first place.
> To me the non-cond uses in VEC_COND_EXPR conceptually look like
> any other unhandled uses that the second loop clears
> vec_cond_expr_only on. But I don't have a testcase, dunno if it is even
> possible.
>
> > use is the rhs1 use comparing that with USE_PTR IIRC. Btw, if you
> > never push VEC_COND_EXPRs with such double-use it's not necessary
> > to check again in the second loop?
>
> I was just trying to be extra cautious in case expand_vector_comparison
> modifies some other stmts, but maybe it is just expand_vector_comparison
> in veclower and no other function that modifies anything but the
> current stmt (+ pushes some new preparation statements and follow-up
> statements).
> So perhaps indeed:
> + if (vec_cond_expr_only)
> + for (gimple *use : uses)
> + {
> + gimple_stmt_iterator it = gsi_for_stmt (use);
> + if (!expand_vector_condition (&it, dce_ssa_names))
> + {
> + vec_cond_expr_only = false;
> + break;
> + }
> + }
> for the second loop is enough.
Yes, I think so.
> But sure, if you prefer all I can do:
> FOR_EACH_IMM_USE_FAST (use_p, iterator, lhs)
> - uses.safe_push (USE_STMT (use_p));
> + if (!is_gimple_debug (USE_STMT (use_p)))
> + uses.safe_push (USE_STMT (use_p));
>
> and keep the rest for GCC 13.
No, I think the change is fine with the second loop adjusted.
Thanks,
Richard.
