[Bug tree-optimization/110474] Vect: the epilog vect loop should have small VF if the loop is unrolled during vectorization

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110474

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

https://gcc.gnu.org/g:7339e725b995912747c01c3ec80ce602512f45df

commit r14-2335-g7339e725b995912747c01c3ec80ce602512f45df
Author: Hao Liu <hliu@os.amperecomputing.com>
Date:   Thu Jul 6 10:03:47 2023 +0800

    tree-optimization/110474 - Vect: select small VF for epilog of unrolled
loop

    If a loop is unrolled during vectorization (i.e. suggested_unroll_factor >
1),
    the VFs of both main and epilog loop are enlarged.  The epilog vect loop is
    specific for a loop with small iteration counts, so a large VF may hurt
    performance.

    This patch unscales the main loop VF by suggested_unroll_factor while
selecting
    the epilog loop VF, so that it will be the same as vectorized loop without
    unrolling (i.e. suggested_unroll_factor = 1).

    gcc/ChangeLog:

            PR tree-optimization/110474
            * tree-vect-loop.cc (vect_analyze_loop_2): unscale the VF by
suggested
            unroll factor while selecting the epilog vect loop VF.

    gcc/testsuite/ChangeLog:

            * gcc.target/aarch64/pr110474.c: New testcase.