re PR tree-optimization/50213 (Regression in space-optimized code relative to 4.5.x)

2011-09-07  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/50213
	* tree-flow.h (simple_iv_increment_p): Declare.
	* tree-ssa-dom.c (simple_iv_increment_p): Export.  Also handle
	POINTER_PLUS_EXPR.
	* tree-ssa-forwprop.c (ssa_forward_propagate_and_combine): Do
	not propagate simple IV counter increments.

From-SVN: r178633

gcc/ChangeLog

+2011-09-07  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/50213
+	* tree-flow.h (simple_iv_increment_p): Declare.
+	* tree-ssa-dom.c (simple_iv_increment_p): Export.  Also handle
+	POINTER_PLUS_EXPR.
+	* tree-ssa-forwprop.c (ssa_forward_propagate_and_combine): Do
+	not propagate simple IV counter increments.
+
 2011-09-07  Eric Botcazou  <ebotcazou@adacore.com>
 	    Iain Sandoe  <iains@gcc.gnu.org>
 

gcc/tree-flow.h

@@ -597,6 +597,7 @@ extern void dump_dominator_optimization_stats (FILE *);
 extern void debug_dominator_optimization_stats (void);
 int loop_depth_of_name (tree);
 tree degenerate_phi_result (gimple);
+bool simple_iv_increment_p (gimple);
 
 /* In tree-ssa-copy.c  */
 extern void propagate_value (use_operand_p, tree);

gcc/tree-ssa-dom.c

@@ -1409,9 +1409,10 @@ record_equality (tree x, tree y)
    i_1 = phi (..., i_2)
    i_2 = i_1 +/- ...  */
 
-static bool
+bool
 simple_iv_increment_p (gimple stmt)
 {
+  enum tree_code code;
   tree lhs, preinc;
   gimple phi;
   size_t i;
@@ -1423,12 +1424,13 @@ simple_iv_increment_p (gimple stmt)
   if (TREE_CODE (lhs) != SSA_NAME)
     return false;
 
-  if (gimple_assign_rhs_code (stmt) != PLUS_EXPR
-      && gimple_assign_rhs_code (stmt) != MINUS_EXPR)
+  code = gimple_assign_rhs_code (stmt);
+  if (code != PLUS_EXPR
+      && code != MINUS_EXPR
+      && code != POINTER_PLUS_EXPR)
     return false;
 
   preinc = gimple_assign_rhs1 (stmt);
-
   if (TREE_CODE (preinc) != SSA_NAME)
     return false;
 

gcc/tree-ssa-forwprop.c

@@ -2377,21 +2377,23 @@ ssa_forward_propagate_and_combine (void)
 	      else
 		gsi_next (&gsi);
 	    }
-	  else if (code == POINTER_PLUS_EXPR && can_propagate_from (stmt))
+	  else if (code == POINTER_PLUS_EXPR)
 	    {
-	      if (TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST
+	      tree off = gimple_assign_rhs2 (stmt);
+	      if (TREE_CODE (off) == INTEGER_CST
+		  && can_propagate_from (stmt)
+		  && !simple_iv_increment_p (stmt)
 		  /* ???  Better adjust the interface to that function
 		     instead of building new trees here.  */
 		  && forward_propagate_addr_expr
-		  (lhs,
-		   build1 (ADDR_EXPR,
-			   TREE_TYPE (rhs),
-			   fold_build2 (MEM_REF,
-					TREE_TYPE (TREE_TYPE (rhs)),
-					rhs,
-					fold_convert
-					(ptr_type_node,
-					 gimple_assign_rhs2 (stmt))))))
+		       (lhs,
+			build1_loc (gimple_location (stmt),
+				    ADDR_EXPR, TREE_TYPE (rhs),
+				    fold_build2 (MEM_REF,
+						 TREE_TYPE (TREE_TYPE (rhs)),
+						 rhs,
+						 fold_convert (ptr_type_node,
+							       off)))))
 		{
 		  release_defs (stmt);
 		  todoflags |= TODO_remove_unused_locals;