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diff --git a/source/s_countLeadingZeros64.c b/source/s_countLeadingZeros64.c
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+
+/*============================================================================
+
+This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
+Package, Release 3, by John R. Hauser.
+
+Copyright 2011, 2012, 2013, 2014 The Regents of the University of California
+(Regents).  All Rights Reserved.  Redistribution and use in source and binary
+forms, with or without modification, are permitted provided that the following
+conditions are met:
+
+Redistributions of source code must retain the above copyright notice,
+this list of conditions, and the following two paragraphs of disclaimer.
+Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions, and the following two paragraphs of disclaimer in the
+documentation and/or other materials provided with the distribution.  Neither
+the name of the Regents nor the names of its contributors may be used to
+endorse or promote products derived from this software without specific prior
+written permission.
+
+IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
+SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING
+OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF REGENTS HAS
+BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+REGENTS SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED
+TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE SOFTWARE AND ACCOMPANYING DOCUMENTATION, IF ANY, PROVIDED
+HEREUNDER IS PROVIDED "AS IS".  REGENTS HAS NO OBLIGATION TO PROVIDE
+MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+
+=============================================================================*/
+
+#include <stdint.h>
+#include "platform.h"
+#include "primitives.h"
+
+#ifndef softfloat_countLeadingZeros64
+
+uint_fast8_t softfloat_countLeadingZeros64( uint64_t a )
+{
+    uint_fast8_t count;
+    uint32_t a32;
+
+    count = 0;
+    a32 = a>>32;
+    if ( ! a32 ) {
+        count = 32;
+        a32 = a;
+    }
+    /*------------------------------------------------------------------------
+    | From here, result is current count + count leading zeros of `a32'.
+    *------------------------------------------------------------------------*/
+    if ( a32 < 0x10000 ) {
+        count += 16;
+        a32 <<= 16;
+    }
+    if ( a32 < 0x1000000 ) {
+        count += 8;
+        a32 <<= 8;
+    }
+    count += softfloat_countLeadingZeros8[a32>>24];
+    return count;
+
+}
+
+#endif
+