[Bug tree-optimization/86270] [8/9 Regression] Simple loop needs an extra register and an extra instruction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86270

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed Oct 31 11:57:33 2018
New Revision: 265677

URL: https://gcc.gnu.org/viewcvs?rev=265677&root=gcc&view=rev
Log:
2018-10-31  Richard Biener  <rguent...@suse.de>

        PR middle-end/70359
        PR middle-end/86270
        * tree-outof-ssa.c (insert_backedge_copies): Restrict
        copy generation to useful cases.  Place the copy before
        the definition of the backedge value when possible.

        * gcc.target/i386/pr70359.c: New testcase.
        * gcc.target/i386/pr86270.c: Likewise.

Added:
    trunk/gcc/testsuite/gcc.target/i386/pr70359.c
    trunk/gcc/testsuite/gcc.target/i386/pr86270.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-outof-ssa.c