[PATCH][alias-improvements] Fix last patch

[Richard Guenther]

More testing revealed that the get_val_for fix wasn't correct.  Thus
I have installed the following.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to the 
branch.

Richard.

2009-02-03  Richard Guenther  <rguenther@suse.de>

	Revert
	* tree-ssa-loop-niter.c (chain_of_csts_start): Use NULL_TREE.
	Simplify test for memory referencing statement.
	(get_val_for): Handle &a[i_1] by bailing out.
	(loop_niter_by_eval): Handle get_va_for bailing out.

	* tree-ssa-loop-niter.c (chain_of_csts_start): Use NULL_TREE.
	Simplify test for memory referencing statement.  Exclude
	non-invariant ADDR_EXPRs.

Index: gcc/tree-ssa-loop-niter.c
===================================================================
*** gcc/tree-ssa-loop-niter.c	(revision 143920)
--- gcc/tree-ssa-loop-niter.c	(working copy)
*************** chain_of_csts_start (struct loop *loop,
*** 1966,1972 ****
      return NULL;
  
    code = gimple_assign_rhs_code (stmt);
!   if (gimple_references_memory_p (stmt))
      return NULL;
  
    use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
--- 1966,1975 ----
      return NULL;
  
    code = gimple_assign_rhs_code (stmt);
!   if (gimple_references_memory_p (stmt)
!       || TREE_CODE_CLASS (code) == tcc_reference
!       || (code == ADDR_EXPR
! 	  && !is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
      return NULL;
  
    use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
*************** get_val_for (tree x, tree base)
*** 2064,2072 ****
  			  gimple_expr_type (stmt), rhs1, rhs2);
      }
    else
!     /* We can also end up with for example &a._M_instance[i_1]; for
!        which we just bail out for now.  */
!     return NULL_TREE;
  }
  
  
--- 2067,2073 ----
  			  gimple_expr_type (stmt), rhs1, rhs2);
      }
    else
!     gcc_unreachable ();
  }
  
  
*************** loop_niter_by_eval (struct loop *loop, e
*** 2134,2147 ****
    for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
      {
        for (j = 0; j < 2; j++)
! 	{
! 	  aval[j] = get_val_for (op[j], val[j]);
! 	  if (aval[j] == NULL_TREE)
! 	    {
! 	      fold_undefer_and_ignore_overflow_warnings ();
! 	      return chrec_dont_know;
! 	    }
! 	}
  
        acnd = fold_binary (cmp, boolean_type_node, aval[0], aval[1]);
        if (acnd && integer_zerop (acnd))
--- 2135,2141 ----
    for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
      {
        for (j = 0; j < 2; j++)
! 	aval[j] = get_val_for (op[j], val[j]);
  
        acnd = fold_binary (cmp, boolean_type_node, aval[0], aval[1]);
        if (acnd && integer_zerop (acnd))
*************** loop_niter_by_eval (struct loop *loop, e
*** 2157,2164 ****
        for (j = 0; j < 2; j++)
  	{
  	  val[j] = get_val_for (next[j], val[j]);
! 	  if (!val[j]
! 	      || !is_gimple_min_invariant (val[j]))
  	    {
  	      fold_undefer_and_ignore_overflow_warnings ();
  	      return chrec_dont_know;
--- 2151,2157 ----
        for (j = 0; j < 2; j++)
  	{
  	  val[j] = get_val_for (next[j], val[j]);
! 	  if (!is_gimple_min_invariant (val[j]))
  	    {
  	      fold_undefer_and_ignore_overflow_warnings ();
  	      return chrec_dont_know;