[Bug tree-optimization/70130] New: h264ref fails with verification error starting with r231674

["pthaugen at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70130

            Bug ID: 70130
           Summary: h264ref fails with verification error starting with
                    r231674
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pthaugen at gcc dot gnu.org
                CC: dje at gcc dot gnu.org, rguenth at gcc dot gnu.org,
                    wschmidt at gcc dot gnu.org
  Target Milestone: ---
              Host: powerpc64*-unknown-linux-gnu
            Target: powerpc64*-unknown-linux-gnu
             Build: powerpc64*-unknown-linux-gnu

Created attachment 37891
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37891&action=edit
.i containing loop

CPU2006 benchmark 464.h264ref started failing with a verification error with
r231674. I have been having a hard time tracking down the exact problem, but
have isolated it down to a specific loop. The attached file is the .i from that
specific loop from benchmark file block.c:intrapred_luma_16x16().

Compile cmd: gcc -c   -m64 -O3 -mcpu=power7  -fsigned-char    Loop_err.c


Prior to r231674 the loop was not vectorized when specifying -mcpu=power7 and
the benchmark ran fine.

Note that the benchmark passes both before/after if built with -mcpu=power8. In
this case the loop was already being vectorized prior to r231674, but with
r231674 it looks like the loop is eliminated (peeled?).

Also note that when I run the benchmark on one of our Power7 boxes, it passes
if I link the .o files with the distro ld (2.20), but fails when using a newer
version (2.22 or 2.25).