[Bug tree-optimization/110702] [12/13 Regression] Wrong code at -O1 on x86_64-linux-gnu (regression since GCC-12.2)

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110702

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:5ca9aea695396266b7eb7d2a065e6f2e9546047e

commit r13-7752-g5ca9aea695396266b7eb7d2a065e6f2e9546047e
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Aug 3 13:11:12 2023 +0200

    tree-optimization/110702 - avoid zero-based memory references in IVOPTs

    Sometimes IVOPTs chooses a weird induction variable which downstream
    leads to issues.  Most of the times we can fend those off during costing
    by rejecting the candidate but it looks like the address description
    costing synthesizes is different from what we end up generating so
    the following fixes things up at code generation time.  Specifically
    we avoid the create_mem_ref_raw fallback which uses a literal zero
    address base with the actual base in index2.  For the case in question
    we have the address

      type = unsigned long
      offset = 0
      elements = {
        [0] = &e * -3,
        [1] = (sizetype) a.9_30 * 232,
        [2] = ivtmp.28_44 * 4
      }

    from which we code generate the problematical

      _3 = MEM[(long int *)0B + ivtmp.36_9 + ivtmp.28_44 * 4];

    which references the object at address zero.  The patch below
    recognizes the fallback after the fact and transforms the
    TARGET_MEM_REF memory reference into a LEA for which this form
    isn't problematic:

      _24 = &MEM[(long int *)0B + ivtmp.36_34 + ivtmp.28_44 * 4];
      _3 = *_24;

    hereby avoiding the correctness issue.  We'd later conclude the
    program terminates at the null pointer dereference and make the
    function pure, miscompling the main function of the testcase.

            PR tree-optimization/110702
            * tree-ssa-loop-ivopts.cc (rewrite_use_address): When
            we created a NULL pointer based access rewrite that to
            a LEA.

            * gcc.dg/torture/pr110702.c: New testcase.

    (cherry picked from commit 13dfb01e5c30c3bd09333ac79d6ff96a617fea67)