[Bug tree-optimization/21639] New: poisoned ggc memory used for -ftree-vectorize

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

The SPEC CPU2000 tests bzip2, gap, and gcc cause mainline GCC to
segfault when built on powerpc64-linux with:
                                                                                
  -m32 -O2 -ftree-vectorize -maltivec -mabi=altivec \
  --param ggc-min-expand=0 --param ggc-min-heapsize=0
                                                                                
Every single CPU2000 test fails to build with those options and -m64
instead of -m32.  gap, facerec, and apsi sometimes fail with -m64
without the ggc params defined, as mentioned in comment 4 of PR 21155.
                                                                                
This minimized test case demonstrates the bug:
                                                                                
extern void bar (unsigned char *, int, int);
unsigned char l[6][4];
int c[6][4];
                                                                                
void
foo (int n, int a)
{
  int t, i;
  int x;
                                                                                
  for (t = 0; t < n; t++)
    {
      for (i = 0; i < a; i++)
        x = l[t][i];
      bar (&l[t][0], x, a);
    }
}
                                                                                
gdb shows the segfault at gcc/tree-chrec.c:1048 ct=0xa5a5a5a5.
                                                                                
The backtrace is too messy for cut-and-paste but shows
  chrec_convert
  interpret_rhs_modify_expr
  analyze_scalar_evolution_1
  analyze_scalar_evolution
  simple_iv
  number_of_iterations_exit
  number_of_iterations_in_loop
  canonicalize_loop_induction_variables
  tree_unroll_loops_completely
  tree_complete_unroll
  execute_pass_list
  ...
                                                                                
SPEC CPU2000 with the ggc params set to zero all build with "-O2" and
with "-O2 -ftree-loop-linear".
                                                                                
The failure shows up with this patch from radkver:
                                                                                
  http://gcc.gnu.org/ml/gcc-cvs/2005-05/msg00302.html
                                                                                
Just to make things even more interesting, add "-fprofile-generate"
and the test case starts failing in the same place on 20050428 with
this patch from bonzini, which suggests it's a latent bug unrelated
to these patches:
                                                                                
  http://gcc.gnu.org/ml/gcc-cvs/2005-04/msg01463.html

-- 
           Summary: poisoned ggc memory used for -ftree-vectorize
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: janis at gcc dot gnu dot org
                CC: dorit at il dot ibm dot com,gcc-bugs at gcc dot gnu dot
                    org
 GCC build triplet: powerpc64-linux
  GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21639