------------------------------------------------------------------ Sender:Richard Biener <richard.guent...@gmail.com> Sent At:2020 Jan. 9 (Thu.) 20:01 Recipient:Bin.Cheng <amker.ch...@gmail.com> Cc:bin.cheng <bin.ch...@linux.alibaba.com>; GCC Patches <gcc-patches@gcc.gnu.org> Subject:Re: [PATCH GCC11]Improve uninitialized warning with value range info
On Thu, Jan 9, 2020 at 11:17 AM Bin.Cheng <amker.ch...@gmail.com> wrote:
> > I am not quite follow here. Do you mean we collect three cases "i <
> > j", "i < min(j)", "max(i) < j" then
> > call prune_uninit_phi_opnds for all three conditions?
>
> No, I've meant to somehow arrange that the 'preds' passed to
> use_pred_not_overlap_with_undef_path_pred contain all three predicates
> rather than just i < j, thus "expand" fully symbolic predicates.
Seems this would require non-trivial refactoring of the original code.
> > This is another question? because now we simply break out of for loop
> > for finding such condition:
> >
> > - if ((gimple_code (flag_def) == GIMPLE_PHI)
> > - && (gimple_bb (flag_def) == gimple_bb (phi))
> > - && find_matching_predicate_in_rest_chains (the_pred, preds,
> > - num_preds))
> > - break;
> >
> > It's always possible that this flag_def can't prune use predicates
> > against undefined path predicates, while a later one can prune but is
> > skipped?
>
> I don't follow but I also don't want to understand the code too much ;)
>
> I'm fine with the idea and if the patch cannot introudce extra bogus warnings
> let's go with it. Can you amed the comment before the two find_var_cmp_const
> calls? I wonder whether eliding the second sweep when the first didn't find
> any predicate it skipped is worth the trouble.
Thanks for the comments, I updated the patch as attached.
Thanks,
bin
2020-01-08 Bin Cheng <bin.li...@linux.alibaba.com>
* tree-ssa-uninit.c (find_var_cmp_const): New function.
(use_pred_not_overlap_with_undef_path_pred): Call above.
(find_matching_predicate_in_rest_chains): Remove param.
0001-Fix-false-uninitialized-warning-message.patch
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