[PATCH][alias-improvements] Random bugfixes

[Richard Guenther <rguenther at suse dot de>]

This fixes bugs I ran into while removing all traces of the old alias
code.  Split out because the can be separately merged.  The "fix" for
PR37869 is more a workaround, but that bug causes miscompiles on
the branch otherwise.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Richard.

2008-11-25  Richard Guenther  <rguenther@suse.de>

	* tree-data-ref.c (dr_may_alias_p): Use the alias-oracle.

	* tree-tailcall.c (tree_optimize_tail_calls_1): Also split the
	edge from the entry block if we have degenerate PHI nodes in
	the first basic block.

	* gimple.c (gimple_set_bb): Fix off-by-one error.
	* tree-cfg.c (move_block_to_fn): Likewise.

	PR tree-optimization/37869
	* tree-ssa-structalias.c (struct variable_info): Add
	is_nonpointer_var flag.
	(new_var_info): Clear it.
	(perform_var_substitution): Set it.
	(find_what_p_points_to): Use it.

Index: alias-improvements/gcc/gimple.c
===================================================================
*** alias-improvements.orig/gcc/gimple.c	2008-11-25 18:31:51.000000000 +0100
--- alias-improvements/gcc/gimple.c	2008-11-25 18:34:31.000000000 +0100
*************** gimple_set_bb (gimple stmt, basic_block
*** 1901,1907 ****
  	  LABEL_DECL_UID (t) = uid = cfun->cfg->last_label_uid++;
  	  if (old_len <= (unsigned) uid)
  	    {
! 	      unsigned new_len = 3 * uid / 2;
  
  	      VEC_safe_grow_cleared (basic_block, gc, label_to_block_map,
  				     new_len);
--- 1901,1907 ----
  	  LABEL_DECL_UID (t) = uid = cfun->cfg->last_label_uid++;
  	  if (old_len <= (unsigned) uid)
  	    {
! 	      unsigned new_len = 3 * uid / 2 + 1;
  
  	      VEC_safe_grow_cleared (basic_block, gc, label_to_block_map,
  				     new_len);
Index: alias-improvements/gcc/tree-data-ref.c
===================================================================
*** alias-improvements.orig/gcc/tree-data-ref.c	2008-11-25 18:31:51.000000000 +0100
--- alias-improvements/gcc/tree-data-ref.c	2008-11-25 18:35:50.000000000 +0100
*************** dr_may_alias_p (const struct data_refere
*** 1244,1256 ****
    if (disjoint_objects_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b)))
      return false;
  
    if (!addr_a || !addr_b)
      return true;
  
!   /* If the references are based on different static objects, they cannot alias
!      (PTA should be able to disambiguate such accesses, but often it fails to,
!      since currently we cannot distinguish between pointer and offset in pointer
!      arithmetics).  */
    if (TREE_CODE (addr_a) == ADDR_EXPR
        && TREE_CODE (addr_b) == ADDR_EXPR)
      return TREE_OPERAND (addr_a, 0) == TREE_OPERAND (addr_b, 0);
--- 1244,1259 ----
    if (disjoint_objects_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b)))
      return false;
  
+   /* Query the alias oracle.  */
+   if (!refs_may_alias_p (DR_REF (a), DR_REF (b)))
+     return false;
+ 
    if (!addr_a || !addr_b)
      return true;
  
!   /* If the references are based on different static objects, they cannot
!      alias (PTA should be able to disambiguate such accesses, but often
!      it fails to).  */
    if (TREE_CODE (addr_a) == ADDR_EXPR
        && TREE_CODE (addr_b) == ADDR_EXPR)
      return TREE_OPERAND (addr_a, 0) == TREE_OPERAND (addr_b, 0);
Index: alias-improvements/gcc/tree-ssa-structalias.c
===================================================================
*** alias-improvements.orig/gcc/tree-ssa-structalias.c	2008-11-25 18:31:51.000000000 +0100
--- alias-improvements/gcc/tree-ssa-structalias.c	2008-11-25 18:34:31.000000000 +0100
*************** struct variable_info
*** 230,235 ****
--- 230,238 ----
       variable.  This is used for C++ placement new.  */
    unsigned int no_tbaa_pruning : 1;
  
+   /* If found to be a non-pointer variable.  */
+   unsigned int is_nonpointer_var : 1;
+ 
    /* Variable id this was collapsed to due to type unsafety.  Zero if
       this variable was not collapsed.  This should be unused completely
       after build_succ_graph, or something is broken.  */
*************** new_var_info (tree t, unsigned int id, c
*** 377,382 ****
--- 380,386 ----
    ret->is_special_var = false;
    ret->is_unknown_size_var = false;
    ret->is_full_var = false;
+   ret->is_nonpointer_var = false;
    var = t;
    if (TREE_CODE (var) == SSA_NAME)
      var = SSA_NAME_VAR (var);
*************** perform_var_substitution (constraint_gra
*** 2175,2180 ****
--- 2179,2185 ----
  		     "%s is a non-pointer variable, eliminating edges.\n",
  		     get_varinfo (node)->name);
  	  stats.nonpointer_vars++;
+ 	  get_varinfo (i)->is_nonpointer_var = true;
  	  clear_edges_for_node (graph, node);
  	}
      }
*************** find_what_p_points_to (tree p)
*** 4752,4757 ****
--- 4757,4767 ----
        if (vi->is_artificial_var)
  	return false;
  
+       /* ???  Some real variables get eliminated as non-pointers.
+ 	 Workaround this.  See PR37869.  */
+       if (vi->is_nonpointer_var)
+ 	return false;
+ 
        /* See if this is a field or a structure.  */
        if (vi->size != vi->fullsize)
  	{
Index: alias-improvements/gcc/tree-tailcall.c
===================================================================
*** alias-improvements.orig/gcc/tree-tailcall.c	2008-11-25 18:31:51.000000000 +0100
--- alias-improvements/gcc/tree-tailcall.c	2008-11-25 18:34:31.000000000 +0100
*************** tree_optimize_tail_calls_1 (bool opt_tai
*** 913,920 ****
  
        if (!phis_constructed)
  	{
! 	  /* Ensure that there is only one predecessor of the block.  */
! 	  if (!single_pred_p (first))
  	    first = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
  
  	  /* Copy the args if needed.  */
--- 913,922 ----
  
        if (!phis_constructed)
  	{
! 	  /* Ensure that there is only one predecessor of the block
! 	     or if there are existing degenerate PHI nodes.  */
! 	  if (!single_pred_p (first)
! 	      || !gimple_seq_empty_p (phi_nodes (first)))
  	    first = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
  
  	  /* Copy the args if needed.  */
Index: alias-improvements/gcc/tree-cfg.c
===================================================================
*** alias-improvements.orig/gcc/tree-cfg.c	2008-11-25 18:31:11.000000000 +0100
--- alias-improvements/gcc/tree-cfg.c	2008-11-25 18:54:28.000000000 +0100
*************** move_block_to_fn (struct function *dest_
*** 5706,5712 ****
  	  old_len = VEC_length (basic_block, cfg->x_label_to_block_map);
  	  if (old_len <= (unsigned) uid)
  	    {
! 	      new_len = 3 * uid / 2;
  	      VEC_safe_grow_cleared (basic_block, gc,
  				     cfg->x_label_to_block_map, new_len);
  	    }
--- 5713,5719 ----
  	  old_len = VEC_length (basic_block, cfg->x_label_to_block_map);
  	  if (old_len <= (unsigned) uid)
  	    {
! 	      new_len = 3 * uid / 2 + 1;
  	      VEC_safe_grow_cleared (basic_block, gc,
  				     cfg->x_label_to_block_map, new_len);
  	    }