[Bug tree-optimization/100727] New: [12 Regression] Recent change to WITH_SIZE_EXPR handling breaks mn10300-elf

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100727

            Bug ID: 100727
           Summary: [12 Regression] Recent change to WITH_SIZE_EXPR
                    handling breaks mn10300-elf
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: law at gcc dot gnu.org
  Target Milestone: ---

This change:
2e6ad1ba532fe684633edac766c598be19ad3b59 is the first bad commit
commit 2e6ad1ba532fe684633edac766c598be19ad3b59
Author: Richard Biener <rguenther@suse.de>
Date:   Wed May 19 10:20:37 2021 +0200

    Enable more WITH_SIZE_EXPR processing

    This enables the alias machinery for WITH_SIZE_EXPR which can appear
    in call LHS and arguments.  In particular this drops the NULL
    return from get_base_address and it adjusts get_ref_base_and_extent
    and friends to use the size information in WITH_SIZE_EXPR and
    look through it for further processing.

    2021-05-19  Richard Biener  <rguenther@suse.de>

            * builtins.c (get_object_alignment_1): Strip outer
            WITH_SIZE_EXPR.
            * tree-dfa.c (get_ref_base_and_extent): Handle outer
            WITH_SIZE_EXPR for size processing and process the
            containing ref.
            * tree-ssa-alias.c (ao_ref_base_alias_set): Strip
            outer WITH_SIZE_EXPR.
            (ao_ref_base_alias_ptr_type): Likewise.
            (refs_may_alias_p_2): Allow WITH_SIZE_EXPR in ref->ref
            and handle that accordingly, stripping it for the
            core alias workers.
            * tree.c (get_base_address): Handle WITH_SIZE_EXPR by
            looking through it instead of returning NULL.

Causes a correctness regression on mn10300-elf for
c-torture/execute/20020412-1.c at -O2.  It appears to me that the assignments
to x and y before the call to foo get erroneously removed.

What's particularly interesting here is the .optimized dumps are the same, but
the .expand dumps differ significantly.  Obviously this points to a problem not
in how this change affects the gimple optimizers, but how it affects the
gimple/tree->RTL translation.

http://3.14.90.209:8080/job/mn10300-elf/