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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/105517] New: [13 Regression] Missing
 diagnostic after recent optimizer improvements
Date: Sat, 07 May 2022 15:12:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105517

            Bug ID: 105517
           Summary: [13 Regression] Missing diagnostic after recent
                    optimizer improvements
           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:

commit ee1cb43bc76de800efa0ade687b0cd28e62a5f82
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jan 26 15:34:54 2022 +0100

    tree-optimization/104162 - CSE of &MEM[ptr].a[i] and ptr + CST

    This adds the capability to value-numbering of treating complex
    address expressions where the offset becomes invariant as equal
    to a POINTER_PLUS_EXPR.  This restores CSE that is now prevented
    by early lowering of &MEM[ptr + CST] to a POINTER_PLUS_EXPR.

    Unfortunately this regresses gcc.dg/asan/pr99673.c again, so
    the testcase is adjusted accordingly.

    2022-01-26  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/104162
            * tree-ssa-sccvn.cc (vn_reference_lookup): Handle
            &MEM[_1 + 5].a[i] like a POINTER_PLUS_EXPR if the offset
            becomes invariant.
            (vn_reference_insert): Likewise.

            * gcc.dg/tree-ssa/ssa-fre-99.c: New testcase.
            * gcc.dg/asan/pr99673.c: Adjust.


Is causing various ports (ft32-elf for example) to fail the Warray-bounds.c
test:

Running /home/jlaw/test/gcc/gcc/testsuite/gcc.dg/dg.exp ...
FAIL: c-c++-common/Warray-bounds.c  -Wc++-compat   (test for warnings, line
187)
FAIL: c-c++-common/Warray-bounds.c  -Wc++-compat   (test for warnings, line
188)

I think you ought to be able to see this with just a cross compiler and
shouldn't need a full cross environment.  I haven't debugged this in any way
other than bisection.=