[Ada] Fix wrong number of iterations for specific loop

[Eric Botcazou]

This is a regression present on all the active branches.  The compiler 
generates code that doesn't execute the expected number of iterations for a 
loop with a dynamic upper bound whose value is exactly the upper bound of the 
base index type and is obtained through a narrowing conversion.

Tested on x86_64-suse-linux, applied on all the active branches.


2013-08-13  Eric Botcazou  <ebotca...@adacore.com>

        * gcc-interface/trans.c (can_equal_min_or_max_val_p): Be prepared for
        values outside of the range of the type.


2013-08-13  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/loop_optimization16.adb: New test.
        * gnat.dg/loop_optimization16_pkg.ad[sb]: New helper.


-- 
Eric Botcazou

Index: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c	(revision 201622)
+++ gcc-interface/trans.c	(working copy)
@@ -2391,7 +2391,10 @@ can_equal_min_or_max_val_p (tree val, tr
   if (TREE_CODE (val) != INTEGER_CST)
     return true;
 
-  return tree_int_cst_equal (val, min_or_max_val) == 1;
+  if (max)
+    return tree_int_cst_lt (val, min_or_max_val) == 0;
+  else
+    return tree_int_cst_lt (min_or_max_val, val) == 0;
 }
 
 /* Return true if VAL (of type TYPE) can equal the minimum value of TYPE.

-- { dg-do run }

with Loop_Optimization16_Pkg; use Loop_Optimization16_Pkg;

procedure Loop_Optimization16 is

   Counter : Natural := 0;

   C : constant Natural := F;

   subtype Index_T is Index_Base range 1 .. Index_Base (C);

begin

   for I in Index_T'First .. Index_T'Last loop
      Counter := Counter + 1;
      exit when Counter > 200;
   end loop;

   if Counter > 200 then
      raise Program_Error;
   end if;

end Loop_Optimization16;

package body Loop_Optimization16_Pkg is

  function F return Natural is
  begin
    return Natural (Index_Base'Last);
  end;

end Loop_Optimization16_Pkg;

package Loop_Optimization16_Pkg is

  type Index_Base is range 0 .. 127;

  function F return Natural;

end Loop_Optimization16_Pkg;