From: Richard Guenther <rguenther@suse.de>
Date: Fri, 24 Aug 2007 11:22:44 +0000 (+0000)
Subject: expr.c (get_inner_reference): Do computation of bitoffset from offset in a way we... 
X-Git-Tag: releases/gcc-4.2.2~127
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=774fee44bfc8a5e62ea18048dd94caaa79ec8579;p=thirdparty%2Fgcc.git

expr.c (get_inner_reference): Do computation of bitoffset from offset in a way we can detect overflow reliably.

2007-08-23  Richard Guenther  <rguenther@suse.de>

	* expr.c (get_inner_reference): Do computation of bitoffset
	from offset in a way we can detect overflow reliably.

From-SVN: r127767
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 437088c7d10c..acafeb67802a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2007-08-24  Richard Guenther  <rguenther@suse.de>
+
+	* expr.c (get_inner_reference): Do computation of bitoffset
+	from offset in a way we can detect overflow reliably.
+
 2007-08-22  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/32563
diff --git a/gcc/expr.c b/gcc/expr.c
index 97c8460b856a..4d62318b5e23 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -5690,6 +5690,8 @@ get_inner_reference (tree exp, HOST_WIDE_INT *pbitsize,
 	*pbitsize = tree_low_cst (size_tree, 1);
     }
 
+  *pmode = mode;
+
   /* Compute cumulative bit-offset for nested component-refs and array-refs,
      and find the ultimate containing object.  */
   while (1)
@@ -5774,18 +5776,25 @@ get_inner_reference (tree exp, HOST_WIDE_INT *pbitsize,
  done:
 
   /* If OFFSET is constant, see if we can return the whole thing as a
-     constant bit position.  Otherwise, split it up.  */
-  if (host_integerp (offset, 0)
-      && 0 != (tem = size_binop (MULT_EXPR,
-				 fold_convert (bitsizetype, offset),
-				 bitsize_unit_node))
-      && 0 != (tem = size_binop (PLUS_EXPR, tem, bit_offset))
-      && host_integerp (tem, 0))
-    *pbitpos = tree_low_cst (tem, 0), *poffset = 0;
-  else
-    *pbitpos = tree_low_cst (bit_offset, 0), *poffset = offset;
+     constant bit position.  Make sure to handle overflow during
+     this conversion.  */
+  if (host_integerp (offset, 0))
+    {
+      double_int tem = double_int_mul (tree_to_double_int (offset),
+				       uhwi_to_double_int (BITS_PER_UNIT));
+      tem = double_int_add (tem, tree_to_double_int (bit_offset));
+      if (double_int_fits_in_shwi_p (tem))
+	{
+	  *pbitpos = double_int_to_shwi (tem);
+	  *poffset = NULL_TREE;
+	  return exp;
+	}
+    }
+
+  /* Otherwise, split it up.  */
+  *pbitpos = tree_low_cst (bit_offset, 0);
+  *poffset = offset;
 
-  *pmode = mode;
   return exp;
 }