[Bug c/25572] New: ppc64 -mminimal-toc trashes r30

["anton at samba dot org" <gcc-bugzilla at gcc dot gnu dot org>]

We found this problem when building a ppc64 Linux kernel. It turns out r30 was
not preserved in a function that was using a local TOC. The compiler used was:

gcc version 4.0.3 20051201 (prerelease) (Debian 4.0.2-5)

Although it seems to reproduce on older toolchains too (eg 3.4).

pinskia cut the original test case down to:

/* Compile with -m64 -O2 -mminimal-toc */
int per_cpu__kstat;

int *f()
{
  int *__ptr;
  asm volatile(";%0":"=g"(__ptr):"0"(&per_cpu__kstat));
  return __ptr;
}

/*
.f:
        ld 30,.LCTOC0@toc(2)
        ld 9,.LC0-.LCTOC1(30)
        mr 3,9
#APP
        ;3
#NO_APP

*/


-- 
           Summary: ppc64 -mminimal-toc trashes r30
           Product: gcc
           Version: 4.0.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anton at samba dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25572