utils.c (rest_of_record_type_compilation): Simplify and robustify pattern…

utils.c (rest_of_record_type_compilation): Simplify and robustify pattern machine code for masking operations.

	* gcc-interface/utils.c (rest_of_record_type_compilation): Simplify and
	robustify pattern machine code for masking operations.

From-SVN: r192672

gcc/ada/ChangeLog

 2012-10-22  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* gcc-interface/utils.c (rest_of_record_type_compilation): Simplify and
+	robustify pattern machine code for masking operations.
+
+2012-10-22  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Subprogram_Type>: In
 	type annotation mode, break circularities introduced by AI05-0151.
 

gcc/ada/gcc-interface/utils.c

@@ -1731,19 +1731,23 @@ rest_of_record_type_compilation (tree record_type)
 	      tree offset = TREE_OPERAND (curpos, 0);
 	      align = tree_low_cst (TREE_OPERAND (curpos, 1), 1);
 
-	      /* An offset which is a bitwise AND with a negative power of 2
-		 means an alignment corresponding to this power of 2.  Note
-		 that, as sizetype is sign-extended but nonetheless unsigned,
-		 we don't directly use tree_int_cst_sgn.  */
+	      /* An offset which is a bitwise AND with a mask increases the
+		 alignment according to the number of trailing zeros.  */
 	      offset = remove_conversions (offset, true);
 	      if (TREE_CODE (offset) == BIT_AND_EXPR
-		  && host_integerp (TREE_OPERAND (offset, 1), 0)
-		  && TREE_INT_CST_HIGH (TREE_OPERAND (offset, 1)) < 0)
+		  && TREE_CODE (TREE_OPERAND (offset, 1)) == INTEGER_CST)
 		{
-		  unsigned int pow
-		    = - tree_low_cst (TREE_OPERAND (offset, 1), 0);
-		  if (exact_log2 (pow) > 0)
-		    align *= pow;
+		  unsigned HOST_WIDE_INT mask
+		    = TREE_INT_CST_LOW (TREE_OPERAND (offset, 1));
+		  unsigned int i;
+
+		  for (i = 0; i < HOST_BITS_PER_WIDE_INT; i++)
+		    {
+		      if (mask & 1)
+			break;
+		      mask >>= 1;
+		      align *= 2;
+		    }
 		}
 
 	      pos = compute_related_constant (curpos,