[tree-ssa] New tests

[law at redhat dot com]

These test two bugs found while working on the tree-ssa code.

The first shows a case where Diego's hack to avoid overlapping
lifetimes fails, thus leading to an abort during the out of SSA
translation.

The second shows a case where a commutative expression was not 
commonized due to operand order differences.  This also led to
a case where we created overlapping lifetimes and aborted.

I've checked these into the branch.


typedef struct rs6000_stack {
  int first_gp_reg_save;
} rs6000_stack_t;
extern char regs_ever_live[113];
extern rs6000_stack_t *rs6000_stack_info (void);
void
rs6000_emit_prologue (int i, rs6000_stack_t *info)
{
  if (regs_ever_live[info->first_gp_reg_save + i] || i+info->first_gp_reg_save)
    gen_rtx_REG (info->first_gp_reg_save + i);
}

union tree_node;
typedef union tree_node *tree;
struct tree_common
{
  tree type;
  unsigned lang_flag_0 : 1;
};
union tree_node
{
  struct tree_common common;
};
static void
java_check_regular_methods (tree class_decl)
{
  int saw_constructor = class_decl->common.type->common.lang_flag_0;
  tree class = class_decl->common.type;
  for (;;)
    {
      if (class)
        if (class_decl->common.type)
          bar (class);
    }
}