[Bug tree-optimization/54016] New: tree loop optimizer: no "branch on count" on s390 anymore since revision 185913

[krebbel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54016

             Bug #: 54016
           Summary: tree loop optimizer: no "branch on count" on s390
                    anymore since revision 185913
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: kreb...@gcc.gnu.org


#include <string.h>

void *
foo (void *dest, const void *src)
{
  return memcpy (dest, src, 50000);
}

r185913: gcc -O3 -march=z10 -S:

foo:
.LFB12:
        .cfi_startproc
        lghi    %r4,195
        lgr     %r1,%r2
.L2:
        pfd     1,768(%r3)
        pfd     2,768(%r1)
        aghi    %r4,-1
        mvc     0(256,%r1),0(%r3)
        la      %r1,256(%r1)
        la      %r3,256(%r3)
        jne     .L2
        mvc     0(80,%r1),0(%r3)
        br      %r14

With previous GCCs this used to be:

foo:
.LFB12:
        .cfi_startproc
        lghi    %r4,195
        lgr     %r1,%r2
.L2:
        pfd     1,768(%r3)
        pfd     2,768(%r1)
        mvc     0(256,%r1),0(%r3)
        la      %r1,256(%r1)
        la      %r3,256(%r3)
        brctg   %r4,.L2
        mvc     0(80,%r1),0(%r3)
        br      %r14