From: Eric Botcazou <ebotcazou@adacore.com>
Date: Sun, 26 May 2013 10:06:18 +0000 (+0000)
Subject: trans.c (Attribute_to_gnu): Add kludge to avoid generating an overflow for -1.
X-Git-Tag: releases/gcc-4.7.4~644
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=50bf9f145c75b1fbc372e33610af14a8be328e58;p=thirdparty%2Fgcc.git

trans.c (Attribute_to_gnu): Add kludge to avoid generating an overflow for -1.

	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Last_Bit>: Add kludge
	to avoid generating an overflow for -1.

From-SVN: r199341
---

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index af231667fe6d..3da582dd2d6e 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,8 @@
+2013-05-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Last_Bit>: Add kludge
+	to avoid generating an overflow for -1.
+
 2013-04-11  Release Manager
 
 	* GCC 4.7.3 released.
diff --git a/gcc/ada/gcc-interface/trans.c b/gcc/ada/gcc-interface/trans.c
index aabe9b6bd020..e5f8351242aa 100644
--- a/gcc/ada/gcc-interface/trans.c
+++ b/gcc/ada/gcc-interface/trans.c
@@ -1901,14 +1901,19 @@ Attribute_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p, int attribute)
 	    gnu_result = bitsize_int (bitpos % BITS_PER_UNIT);
 	    gnu_result = size_binop (PLUS_EXPR, gnu_result,
 				     TYPE_SIZE (TREE_TYPE (gnu_prefix)));
-	    gnu_result = size_binop (MINUS_EXPR, gnu_result,
-				     bitsize_one_node);
+	    /* ??? Avoid a large unsigned result that will overflow when
+	       converted to the signed universal_integer.  */
+	    if (integer_zerop (gnu_result))
+	      gnu_result = integer_minus_one_node;
+	    else
+	      gnu_result
+		= size_binop (MINUS_EXPR, gnu_result, bitsize_one_node);
 	    break;
 
 	  case Attr_Bit_Position:
 	    gnu_result = gnu_field_bitpos;
 	    break;
-		}
+	  }
 
 	/* If this has a PLACEHOLDER_EXPR, qualify it by the object we are
 	   handling.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index eda744322b74..e8b54e4fb14b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-05-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/specs/last_bit.ads: New test.
+
 2013-05-13  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/57264
diff --git a/gcc/testsuite/gnat.dg/specs/last_bit.ads b/gcc/testsuite/gnat.dg/specs/last_bit.ads
new file mode 100644
index 000000000000..ecfc2540a8ae
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/specs/last_bit.ads
@@ -0,0 +1,19 @@
+-- { dg-do compile }
+
+package Last_Bit is
+
+   Max_Components : constant := 100;
+   type Count_Type is new Natural range 0 .. Max_Components;
+   subtype Index_Type is Count_Type range 1 .. Count_Type'Last;
+   
+   type List_Type is array (Index_Type range <>) of Integer;
+
+   type Record_Type (Count : Count_Type := 0) is record
+      List : List_Type (1 .. Count);
+   end record;
+
+   Null_Record : Record_Type (Count => 0);
+
+   List_Last_Bit : Integer := Null_Record.List'Last_Bit;
+
+end Last_Bit;