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[Ada] Small tweak to 'for' loop translation
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 13 Dec 2010 18:50:35 +0100
- Subject: [Ada] Small tweak to 'for' loop translation
This avoids generating useless entry tests for 'for' loops in some cases.
Tested on i586-suse-linux, applied on the mainline.
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.
--
Eric Botcazou
Index: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c (revision 167721)
+++ gcc-interface/trans.c (working copy)
@@ -2130,6 +2130,26 @@ can_equal_max_val_p (tree val, tree type
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