[Bug middle-end/101955] (signed<<31)>>31 should become -(signed&1)

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101955

--- Comment #9 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:a3da9adeb457d4f01c4e695a9621f90c2e2a5e68

commit r14-5014-ga3da9adeb457d4f01c4e695a9621f90c2e2a5e68
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Oct 30 16:21:28 2023 +0000

    ARC: Convert (signed<<31)>>31 to -(signed&1) without barrel shifter.

    This patch optimizes PR middle-end/101955 for the ARC backend.  On ARC
    CPUs with a barrel shifter, using two shifts is optimal as:

            asl_s   r0,r0,31
            asr_s   r0,r0,31

    but without a barrel shifter, GCC -O2 -mcpu=em currently generates:

            and     r2,r0,1
            ror     r2,r2
            add.f   0,r2,r2
            sbc     r0,r0,r0

    with this patch, we now generate the smaller, faster and non-flags
    clobbering:

            bmsk_s  r0,r0,0
            neg_s   r0,r0

    2023-10-30  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR middle-end/101955
            * config/arc/arc.md (*extvsi_1_0): New define_insn_and_split
            to convert sign extract of the least significant bit into an
            AND $1 then a NEG when !TARGET_BARREL_SHIFTER.

    gcc/testsuite/ChangeLog
            PR middle-end/101955
            * gcc.target/arc/pr101955.c: New test case.