Use the ARM assembly code in mpi_arm.c for iOS.

nss/mozilla/security/nss/lib/freebl/mpi/mpi_mac.c

+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is the Netscape security libraries.
+ *
+ * The Initial Developer of the Original Code is
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1994-2000
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+/* Include the appropriate assembly code file for Mac OS X and iOS. */
+
+#if defined(__arm__)
+#include "mpi_arm.c"
+#endif

[wtc, 2012/08/02 01:04:29]

Thinking ahead, I realized that the assembly code files for
the other two processor architectures are .s files.  I don't
think this file (a .c file) can include .s files.  So we'll
need to add another .s file for Mac, and I believe that .s
file cannot be named mpi_mac.s.

[Mark Mentovai, 2012/08/02 14:50:34]

wtc wrote:
If you eliminate the two bits of C code in the other file, you can easily make
it an .s file too. You don’t give up the ability to use preprocessor directives
in an .s file on the Mac. On other platforms, you do, but if you name it with a
capital .S, you can continue to use preprocessor directives. .S also works on
the Mac.