tree-ssa-sccvn.c (visit_reference_op_load): If the lookup found an expression with constants, note that in the VN for the lhs.

2008-03-18  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-sccvn.c (visit_reference_op_load): If the lookup
	found an expression with constants, note that in the VN for the lhs.
	* tree-ssa-pre.c (eliminate): Visit COND_EXPR statements and
	fold them to constants if possible.  Run cleanup_cfg if done so.
	(execute_pre): Return todo.
	(do_pre): Likewise.
	(execute_fre): Likewise.
	* tree-ssa-forwprop.c (can_propagate_from): Allow propagation
	of constants.
	(get_prop_source_stmt): Look through pointer conversions.

	* gcc.dg/tree-ssa/forwprop-4.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-16.c: Likewise.

From-SVN: r133315

1 files changed, 48 insertions, 8 deletions

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 616627c..ad628a3 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -3605,10 +3605,11 @@ do_SCCVN_insertion (tree stmt, tree ssa_vn)
 
 /* Eliminate fully redundant computations.  */
 
-static void
+static unsigned int
 eliminate (void)
 {
   basic_block b;
+  unsigned int todo = 0;
 
   FOR_EACH_BB (b)
     {
@@ -3689,8 +3690,46 @@ eliminate (void)
 		    }
 		}
 	    }
+	  /* Visit COND_EXPRs and fold the comparison with the
+	     available value-numbers.  */
+	  else if (TREE_CODE (stmt) == COND_EXPR
+		   && COMPARISON_CLASS_P (COND_EXPR_COND (stmt)))
+	    {
+	      tree cond = COND_EXPR_COND (stmt);
+	      tree op0 = TREE_OPERAND (cond, 0);
+	      tree op1 = TREE_OPERAND (cond, 1);
+	      tree result;
+
+	      if (TREE_CODE (op0) == SSA_NAME)
+		op0 = VN_INFO (op0)->valnum;
+	      if (TREE_CODE (op1) == SSA_NAME)
+		op1 = VN_INFO (op1)->valnum;
+	      result = fold_binary (TREE_CODE (cond), TREE_TYPE (cond),
+				    op0, op1);
+	      if (result && TREE_CODE (result) == INTEGER_CST)
+		{
+		  COND_EXPR_COND (stmt) = result;
+		  update_stmt (stmt);
+		  todo = TODO_cleanup_cfg;
+		}
+	    }
+	  else if (TREE_CODE (stmt) == COND_EXPR
+		   && TREE_CODE (COND_EXPR_COND (stmt)) == SSA_NAME)
+	    {
+	      tree op = COND_EXPR_COND (stmt);
+	      op = VN_INFO (op)->valnum;
+	      if (TREE_CODE (op) == INTEGER_CST)
+		{
+		  COND_EXPR_COND (stmt) = integer_zerop (op)
+		    ? boolean_false_node : boolean_true_node;
+		  update_stmt (stmt);
+		  todo = TODO_cleanup_cfg;
+		}
+	    }
 	}
     }
+
+  return todo;
 }
 
 /* Borrow a bit of tree-ssa-dce.c for the moment.
@@ -3931,9 +3970,10 @@ fini_pre (void)
 /* Main entry point to the SSA-PRE pass.  DO_FRE is true if the caller
    only wants to do full redundancy elimination.  */
 
-static void
+static unsigned int
 execute_pre (bool do_fre)
 {
+  unsigned int todo = 0;
 
   do_partial_partial = optimize > 2;
   init_pre (do_fre);
@@ -3947,7 +3987,7 @@ execute_pre (bool do_fre)
       if (!do_fre)
 	remove_dead_inserted_code ();
       fini_pre ();
-      return;
+      return 0;
     }
   switch_to_PRE_table ();
   compute_avail ();
@@ -3978,7 +4018,7 @@ execute_pre (bool do_fre)
     }
 
   /* Remove all the redundant expressions.  */
-  eliminate ();
+  todo |= eliminate ();
 
   if (dump_file && (dump_flags & TDF_STATS))
     {
@@ -3999,6 +4039,8 @@ execute_pre (bool do_fre)
     }
 
   fini_pre ();
+
+  return todo;
 }
 
 /* Gate and execute functions for PRE.  */
@@ -4006,8 +4048,7 @@ execute_pre (bool do_fre)
 static unsigned int
 do_pre (void)
 {
-  execute_pre (false);
-  return TODO_rebuild_alias;
+  return TODO_rebuild_alias | execute_pre (false);
 }
 
 static bool
@@ -4041,8 +4082,7 @@ struct tree_opt_pass pass_pre =
 static unsigned int
 execute_fre (void)
 {
-  execute_pre (true);
-  return 0;
+  return execute_pre (true);
 }
 
 static bool