[Bug target/68483] [5/6 Regression] gcc 5.2: suboptimal code compared to 4.9

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68483

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Tue Nov 24 10:45:52 2015
New Revision: 230797

URL: https://gcc.gnu.org/viewcvs?rev=230797&root=gcc&view=rev
Log:
        PR target/68483
        * tree-vect-generic.c (lower_vec_perm): If VEC_PERM_EXPR
        is valid vec_shr pattern, don't lower it even if can_vec_perm_p
        returns false.
        * optabs.c (shift_amt_for_vec_perm_mask): Return NULL_RTX
        whenever first is nelt or above.  Don't mask expected with
        2 * nelt - 1.

        * gcc.target/i386/pr68483-1.c: New test.
        * gcc.target/i386/pr68483-2.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/i386/pr68483-1.c
    trunk/gcc/testsuite/gcc.target/i386/pr68483-2.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/optabs.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-generic.c