[Bug tree-optimization/83907] missing strlen optimization for non-zero memset followed by a nul byte store

[Bug tree-optimization/83907] missing strlen optimization for non-zero memset followed by a nul byte store

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83907

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-02-20
             Status|UNCONFIRMED                 |ASSIGNED
                 CC|                            |roger at nextmovesoftware dot com
           Assignee|unassigned at gcc dot gnu.org      |roger at nextmovesoftware dot com

--- Comment #1 from Roger Sayle <roger at nextmovesoftware dot com> ---
Patch proposed.
https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590619.html

[Bug tree-optimization/83907] missing strlen optimization for non-zero memset followed by a nul byte store

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83907

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:1fe04c497d5a16baee6af48a0b08ca99b75724e4

commit r13-455-g1fe04c497d5a16baee6af48a0b08ca99b75724e4
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri May 13 22:20:16 2022 +0100

    PR tree-optimization/83907: Improved memset handling in strlen pass.

    This patch implements the missed optimization enhancement PR 83907,
    by handling memset with a constant byte value in tree-ssa's strlen
    optimization pass.  Effectively, this treats memset(dst,'x',3) as
    it would memcpy(dst,"xxx",3).

    This patch also includes a tweak to handle_store to address another
    missed optimization observed in the related test case pr83907-2.c.
    The consecutive byte stores to memory get coalesced into a vector
    write of a vector const, but unfortunately tree-ssa-strlen's
    handle_store didn't previously handle the (unusual) case where the
    stored "string" starts with a zero byte but also contains non-zero
    bytes.

    2022-05-13  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR tree-optimization/83907
            * tree-ssa-strlen.cc (handle_builtin_memset): Record a strinfo
            for memset with an constant char value.
            (handle_store): Improved handling of stores with a first byte
            of zero, but not storing_all_zeros_p.

    gcc/testsuite/ChangeLog
            PR tree-optimization/83907
            * gcc.dg/tree-ssa/pr83907-1.c: New test case.
            * gcc.dg/tree-ssa/pr83907-2.c: New test case.

[Bug tree-optimization/83907] missing strlen optimization for non-zero memset followed by a nul byte store

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83907

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
      Known to work|                            |13.0
   Target Milestone|---                         |13.0
         Resolution|---                         |FIXED

--- Comment #3 from Roger Sayle <roger at nextmovesoftware dot com> ---
This should now be fixed on mainline.