[Bug middle-end/15760] New: Loop unrolling bug with max-unrolled-insns=200

["micis at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

It was stated that in the second prerelease of GCC-3.3.4 from 30 May 2004
the -funroll-loop miscompilation has been fixed.

That is true for the default option set. 

However, if you use the options

    -O2 -funroll-loops --param max-unrolled-insns=xxx

execution of memcpy-1.c will still fail for all xxx > 192
(I only tested PowerPC target)

On PowerPC (G5) I found that --param max-unrolled-insns=600 results 
in about 20% - 30% higher speed in my application (mostly Altivec image
processing).

Michael Cieslinski

-- 
           Summary: Loop unrolling bug with max-unrolled-insns=200
           Product: gcc
           Version: 3.3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: micis at gmx dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-unknown-linux-gnu
  GCC host triplet: powerpc-unknown-linux-gnu
GCC target triplet: powerpc-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15760