tree.c (range_in_array_bounds_p): New predicate.

	* tree.c (range_in_array_bounds_p): New predicate.
	* tree.h (range_in_array_bounds_p): Declare it.
	* tree-eh.c (tree_could_trap_p) <ARRAY_RANGE_REF>: Use it to
	return a less conservative answer.
	* tree-sra.c (struct sra_elt): Add new pointer field 'groups'
	and flag 'is_group'.
	(IS_ELEMENT_FOR_GROUP): New macro.
	(FOR_EACH_ACTUAL_CHILD): Likewise.
	(next_child_for_group): New helper function.
	(can_completely_scalarize_p): Take into account groups.
	(sra_hash_tree): Handle RANGE_EXPR.
	(sra_elt_eq): Likewise.
	(lookup_element): Be prepared for handling groups.
	(is_valid_const_index): Delete.
	(maybe_lookup_element_for_expr) <ARRAY_REF>: Use in_array_bounds_p
	instead of is_valid_const_index.
	<ARRAY_RANGE_REF>: New case.
	(sra_walk_expr) <ARRAY_REF>: Use in_array_bounds_p instead of
	is_valid_const_index.
	<ARRAY_RANGE_REF>: Do not unconditionally punt.
	(scan_dump): Dump info for groups too.
	(decide_instantiation_1): Likewise.
	(decide_block_copy): Assert that the element is not a group.
	Propagate decision to groups.
	(generate_one_element_ref): Handle RANGE_EXPR.
	(mark_no_warning): Iterate over actual childs.
	(generate_copy_inout): Likewise.
	(generate_element_copy): Likewise.
	(generate_element_zero): Likewise.
	(generate_element_init_1): Likewise.
	(dump_sra_elt_name): Handle RANGE_EXPR.

From-SVN: r115160

gcc/ChangeLog

+2006-07-03  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* tree.c (range_in_array_bounds_p): New predicate.
+	* tree.h (range_in_array_bounds_p): Declare it.
+	* tree-eh.c (tree_could_trap_p) <ARRAY_RANGE_REF>: Use it to
+	return a less conservative answer.
+	* tree-sra.c (struct sra_elt): Add new pointer field 'groups'
+	and flag 'is_group'.
+	(IS_ELEMENT_FOR_GROUP): New macro.
+	(FOR_EACH_ACTUAL_CHILD): Likewise.
+	(next_child_for_group): New helper function.
+	(can_completely_scalarize_p): Take into account groups.
+	(sra_hash_tree): Handle RANGE_EXPR.
+	(sra_elt_eq): Likewise.
+	(lookup_element): Be prepared for handling groups.
+	(is_valid_const_index): Delete.
+	(maybe_lookup_element_for_expr) <ARRAY_REF>: Use in_array_bounds_p
+	instead of is_valid_const_index.
+	<ARRAY_RANGE_REF>: New case.
+	(sra_walk_expr) <ARRAY_REF>: Use in_array_bounds_p instead of
+	is_valid_const_index.
+	<ARRAY_RANGE_REF>: Do not unconditionally punt.
+	(scan_dump): Dump info for groups too.
+	(decide_instantiation_1): Likewise.
+	(decide_block_copy): Assert that the element is not a group.
+	Propagate decision to groups.
+	(generate_one_element_ref): Handle RANGE_EXPR.
+	(mark_no_warning): Iterate over actual childs.
+	(generate_copy_inout): Likewise.
+	(generate_element_copy): Likewise.
+	(generate_element_zero): Likewise.
+	(generate_element_init_1): Likewise.
+	(dump_sra_elt_name): Handle RANGE_EXPR.
+
 2006-07-03  Roger Sayle  <roger@eyesopen.com>
 
 	PR tree-optimization/26251

gcc/testsuite/ChangeLog

+2006-07-03  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/gnat.dg/string_slice.adb: New test.
+
 2006-07-01  Tobias Schlter  <tobias.schlueter@physik.uni-muenchen.de>
 
 	PR fortran/19259

gcc/testsuite/gnat.dg/string_slice.adb

+-- { dg-do run }
+-- { dg-options "-O" }
+
+procedure string_slice is
+
+   subtype Key_T is String (1 .. 3);
+
+   function One_Xkey return Key_T is
+      Key : Key_T := "XXX";
+   begin
+      Key (1 .. 2) := "__";
+      return Key;
+   end;
+
+   Key : Key_T := One_Xkey;
+
+begin
+   if Key (3) /= 'X' then
+      raise Program_Error;
+   end if;
+end;

gcc/tree-eh.c

@@ -1889,13 +1889,14 @@ tree_could_trap_p (tree expr)
       goto restart;
 
     case ARRAY_RANGE_REF:
-      /* Let us be conservative here for now.  We might be checking bounds of
-	 the access similarly to the case below.  */
-      if (!TREE_THIS_NOTRAP (expr))
+      base = TREE_OPERAND (expr, 0);
+      if (tree_could_trap_p (base))
 	return true;
 
-      base = TREE_OPERAND (expr, 0);
-      return tree_could_trap_p (base);
+      if (TREE_THIS_NOTRAP (expr))
+	return false;
+
+      return !range_in_array_bounds_p (expr);
 
     case ARRAY_REF:
       base = TREE_OPERAND (expr, 0);

gcc/tree.c

@@ -6892,6 +6892,39 @@ in_array_bounds_p (tree ref)
   return true;
 }
 
+/* Returns true if it is possible to prove that the range of
+   an array access REF (an ARRAY_RANGE_REF expression) falls
+   into the array bounds.  */
+
+bool
+range_in_array_bounds_p (tree ref)
+{
+  tree domain_type = TYPE_DOMAIN (TREE_TYPE (ref));
+  tree range_min, range_max, min, max;
+
+  range_min = TYPE_MIN_VALUE (domain_type);
+  range_max = TYPE_MAX_VALUE (domain_type);
+  if (!range_min
+      || !range_max
+      || TREE_CODE (range_min) != INTEGER_CST
+      || TREE_CODE (range_max) != INTEGER_CST)
+    return false;
+
+  min = array_ref_low_bound (ref);
+  max = array_ref_up_bound (ref);
+  if (!min
+      || !max
+      || TREE_CODE (min) != INTEGER_CST
+      || TREE_CODE (max) != INTEGER_CST)
+    return false;
+
+  if (tree_int_cst_lt (range_min, min)
+      || tree_int_cst_lt (max, range_max))
+    return false;
+
+  return true;
+}
+
 /* Return true if T (assumed to be a DECL) is a global variable.  */
 
 bool

gcc/tree.h

@@ -3576,6 +3576,7 @@ extern tree build_complex_type (tree);
 extern tree build_resx (int);
 extern tree array_type_nelts (tree);
 extern bool in_array_bounds_p (tree);
+extern bool range_in_array_bounds_p (tree);
 
 extern tree value_member (tree, tree);
 extern tree purpose_member (tree, tree);