src/java.base/share/classes/java/lang/StrictMath.java

rev 12758 : 5100935: No way to access the 64-bit integer multiplication of 64-bit CPUs efficiently
Summary: Add a method to produce the high 64 bits of two 64-bit longs multiplied into a 128-bit long.
Reviewed-by: XXX

@@ -828,10 +828,38 @@
     public static int toIntExact(long value) {
         return Math.toIntExact(value);
     }
 
     /**
+     * Returns the product of the arguments allowing overflowed values within
+     * the range of {@code long}.
+     *
+     * @param x the first value
+     * @param y the second value
+     * @return the result
+     * @see Math#multiplyFull(long,long)
+     * @since 1.9
+     */
+    public static long multiplyFull(int x, int y) {
+        return Math.multiplyFull(x, y);
+    }
+
+    /**
+     * Returns as a {@code long} the most significant 64 bits of the 128-bit
+     * product of two 64-bit factors.
+     *
+     * @param x the first value
+     * @param y the second value
+     * @return the result
+     * @see Math#multiplyHigh(long,long)
+     * @since 1.9
+     */
+    public static long multiplyHigh(long x, long y) {
+        return Math.multiplyHigh(x, y);
+    }
+
+    /**
      * Returns the largest (closest to positive infinity)
      * {@code int} value that is less than or equal to the algebraic quotient.
      * There is one special case, if the dividend is the
      * {@linkplain Integer#MIN_VALUE Integer.MIN_VALUE} and the divisor is {@code -1},
      * then integer overflow occurs and