[Bug target/105991] [12/13 Regression] rldicl+sldi+add generated instead of rldimi

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105991

--- Comment #6 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:4306339798b6843937c628c5ece8c234b309b13d

commit r13-1191-g4306339798b6843937c628c5ece8c234b309b13d
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Wed Jun 22 00:08:56 2022 +0100

    PR target/105991: Recognize PLUS and XOR forms of rldimi in rs6000.md.

    This patch addresses PR target/105991 where a change to prefer representing
    shifts and adds at the tree-level as multiplications, causes problems for
    the rldimi patterns in the powerpc backend.  The issue is that rs6000.md
    models this pattern using IOR, and some variants that have the equivalent
    PLUS or XOR in the RTL fail to match some *rotl<mode>4_insert patterns.
    This is fixed in this patch by adding a define_insn_and_split to locally
    canonicalize the PLUS and XOR forms to the backend's preferred IOR form.

    An alternative fix might be for the RTL optimizers to define a canonical
    form for these plus_xor_ior equivalent expressions, but the logical
    choice might be plus (which may appear in an addressing mode), and such
    a change may require a number of tweaks to update various backends
    (i.e.  a more intrusive change than the one proposed here).

    Many thanks for Marek Polacek for bootstrapping and regression testing
    this change without problems.

    2022-06-22  Roger Sayle  <roger@nextmovesoftware.com>
                Marek Polacek  <polacek@redhat.com>
                Segher Boessenkool  <segher@kernel.crashing.org>
                Kewen Lin  <linkw@linux.ibm.com>

    gcc/ChangeLog
            PR target/105991
            * config/rs6000/rs6000.md (rotl<mode>3_insert_3): Check that
            exact_log2 doesn't return -1 (or zero).
            (plus_xor): New code iterator.
            (*rotl<mode>3_insert_3_<code>): New define_insn_and_split.

    gcc/testsuite/ChangeLog
            PR target/105991
            * gcc.target/powerpc/pr105991.c: New test case.