On Tue, Apr 05, 2022 at 03:07:53PM +0200, Richard Biener wrote:
> The following avoids expanding definitions in regions conditionally
> executed under the condition A when simplifying A && B or A || B.
> This is done by passing down the basic-block of the outer condition
> to maybe_fold_{and,or}_comparisons, through the various helpers
> in gimple-fold.cc that might call back to maybe_fold_{and,or}_comparisons
> and ultimatively to maybe_fold_comparisons_from_match_pd where the
> fix is to provide a custom valueization hook to
> gimple_match_op::resimplify that avoids looking at definitions
> that do not dominate the outer block.
>
> For the testcase this avoids combining a stmt that invokes undefined
> integer overflow when the outer condition is false but it also
> aovids combining stmts with range information that is derived from
> the outer condition.
>
> The new parameter to maybe_fold_{and,or}_comparisons is defaulted
> to nullptr and I only adjusted the if-combine to pass down the
> outer block. I think other callers like tree-if-conv have the
> same issue but it's not straight-forward as to what to do there.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> Any opinions? (I'm not 100% there's not other code besides
> maybe_fold_comparisons_from_match_pd in the call chains that
> need to check against the BB - some pieces do look at the
> definition of a stmt. Though I think the proper TLC here
> is to move what's missing to match.pd and get rid of the
> "manual duplication" there)
>
> Thanks,
> Richard.
>
> 2022-04-05 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/105142
> * gimple-fold.h (maybe_fold_and_comparisons): Add defaulted
> basic-block parameter.
> (maybe_fold_or_comparisons): Likewise.
> * gimple-fold.cc (follow_outer_ssa_edges): New.
> (maybe_fold_comparisons_from_match_pd): Use follow_outer_ssa_edges
> when an outer condition basic-block is specified.
> (and_comparisons_1, and_var_with_comparison,
> and_var_with_comparison_1, or_comparisons_1,
> or_var_with_comparison, or_var_with_comparison_1): Receive and pass
> down the outer condition basic-block.
> * tree-ssa-ifcombine.cc (ifcombine_ifandif): Pass down the
> basic-block of the outer condition.
>
> * g++.dg/torture/pr105142.C: New testcase.
LGTM.
Jakub
