[Bug tree-optimization/71343] missed optimization (can't "prove" shift and multiplication equivalence)

[Bug tree-optimization/71343] missed optimization (can't "prove" shift and multiplication equivalence)

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71343

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug tree-optimization/71343] missed optimization (can't "prove" shift and multiplication equivalence)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71343

--- Comment #3 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:03acd8b6429e22068330dce5abf129291d3f26de

commit r13-2047-g03acd8b6429e22068330dce5abf129291d3f26de
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Aug 15 17:32:26 2022 +0100

    PR tree-optimization/71343: Optimize (X<<C)&(Y<<C) as (X&Y)<<C.

    This patch is the first part of a solution to PR tree-optimization/71343,
    a missed-optimization enhancement request where GCC fails to see that
    (a<<2)+(b<<2) == a*4+b*4.

    This piece is that (X<<C) op (Y<<C) can be simplified to (X op Y) << C,
    for many binary operators, including AND, IOR, XOR, and (if overflow
    isn't an issue) PLUS and MINUS.  Likewise, the right shifts (both logical
    and arithmetic) and bit-wise logical operators can be simplified in a
    similar fashion.  These all reduce the number of GIMPLE binary operations
    from 3 to 2, by combining/eliminating a shift operation.

    2022-08-15  Roger Sayle  <roger@nextmovesoftware.com>
                Richard Biener  <rguenther@suse.de>

    gcc/ChangeLog
            PR tree-optimization/71343
            * match.pd (op (lshift @0 @1) (lshift @2 @1)): Optimize the
            expression (X<<C) + (Y<<C) to (X+Y)<<C for multiple operators.
            (op (rshift @0 @1) (rshift @2 @1)): Likewise, simplify
(X>>C)^(Y>>C)
            to (X^Y)>>C for binary logical operators, AND, IOR and XOR.

    gcc/testsuite/ChangeLog
            PR tree-optimization/71343
            * gcc.dg/pr71343-1.c: New test case.

[Bug tree-optimization/71343] missed optimization (can't "prove" shift and multiplication equivalence)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71343

--- Comment #4 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:98837d6e79dd27c15f5218f3f1ddf838cda4796c

commit r13-5111-g98837d6e79dd27c15f5218f3f1ddf838cda4796c
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Wed Jan 11 16:54:58 2023 +0000

    PR tree-optimization/71343: Value number X<<2 as X*4.

    This patch is the second part of a fix for PR tree-optimization/71343,
    that implements Richard Biener's suggestion of using tree-ssa's value
    numbering instead of match.pd.  The change is that when assigning a
    value number for the expression X<<C, we actually look-up or insert
    the value number for the multiplication X*(1<<C).  This elegantly
    handles the fact that we (intentionally) don't canonicalize these as
    equivalent in GIMPLE, and the optimization/equivalence in PR 71343 now
    happens by (tree-ssa SCCVN) magic.

    2023-01-11  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR tree-optimization/71343
            * tree-ssa-sccvn.cc (visit_nary_op) <case LSHIFT_EXPR>: Make
            the value number of the expression X << C the same as the value
            number for the multiplication X * (1<<C).

    gcc/testsuite/ChangeLog
            PR tree-optimization/71343
            * gcc.dg/pr71343-2.c: New test case.

[Bug tree-optimization/71343] missed optimization (can't "prove" shift and multiplication equivalence)

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71343

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |13.0
                 CC|                            |roger at nextmovesoftware dot com
         Resolution|---                         |FIXED

--- Comment #5 from Roger Sayle <roger at nextmovesoftware dot com> ---
This should now be fixed on mainline.