* gcc-interface/trans.c (can_be_lower_p): New predicate.

	(Loop_Statement_to_gnu): Do not generate the entry condition if we know
	that it will be true.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@167757 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index b4af763..a42758d 100644 (file)
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,9 @@
+2010-12-13  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * gcc-interface/trans.c (can_be_lower_p): New predicate.
+       (Loop_Statement_to_gnu): Do not generate the entry condition if we know
+       that it will be true.
+
 2010-12-03  Joseph Myers  <joseph@codesourcery.com>
 
        * gcc-interface/lang.opt (k8): New option.

diff --git a/gcc/ada/gcc-interface/trans.c b/gcc/ada/gcc-interface/trans.c
index b658620..8a15c2d 100644 (file)
--- a/gcc/ada/gcc-interface/trans.c
+++ b/gcc/ada/gcc-interface/trans.c
@@ -2130,6 +2130,26 @@ can_equal_max_val_p (tree val, tree type, bool reverse)
   return can_equal_min_or_max_val_p (val, type, !reverse);
 }
 
+/* Return true if VAL1 can be lower than VAL2.  */
+
+static bool
+can_be_lower_p (tree val1, tree val2)
+{
+  if (TREE_CODE (val1) == NOP_EXPR)
+    val1 = TYPE_MIN_VALUE (TREE_TYPE (TREE_OPERAND (val1, 0)));
+
+  if (TREE_CODE (val1) != INTEGER_CST)
+    return true;
+
+  if (TREE_CODE (val2) == NOP_EXPR)
+    val2 = TYPE_MAX_VALUE (TREE_TYPE (TREE_OPERAND (val2, 0)));
+
+  if (TREE_CODE (val2) != INTEGER_CST)
+    return true;
+
+  return tree_int_cst_lt (val1, val2);
+}
+
 /* Subroutine of gnat_to_gnu to translate gnat_node, an N_Loop_Statement,
    to a GCC tree, which is returned.  */
 
@@ -2297,16 +2317,19 @@ Loop_Statement_to_gnu (Node_Id gnat_node)
        LOOP_STMT_BOTTOM_COND_P (gnu_loop_stmt) = 1;
 
       /* If we use the BOTTOM_COND, we can turn the test into an inequality
-        test but we have to add an ENTRY_COND to protect the empty loop.  */
+        test but we may have to add ENTRY_COND to protect the empty loop.  */
       if (LOOP_STMT_BOTTOM_COND_P (gnu_loop_stmt))
        {
          test_code = NE_EXPR;
-         gnu_cond_expr
-           = build3 (COND_EXPR, void_type_node,
-                     build_binary_op (LE_EXPR, boolean_type_node,
-                                      gnu_low, gnu_high),
-                     NULL_TREE, alloc_stmt_list ());
-         set_expr_location_from_node (gnu_cond_expr, gnat_loop_spec);
+         if (can_be_lower_p (gnu_high, gnu_low))
+           {
+             gnu_cond_expr
+               = build3 (COND_EXPR, void_type_node,
+                         build_binary_op (LE_EXPR, boolean_type_node,
+                                          gnu_low, gnu_high),
+                         NULL_TREE, alloc_stmt_list ());
+             set_expr_location_from_node (gnu_cond_expr, gnat_loop_spec);
+           }
        }
 
       /* Open a new nesting level that will surround the loop to declare the