RFR: 8264762: ByteBuffer.byteOrder(BIG_ENDIAN).asXBuffer.put(Xarray) and ByteBuffer.byteOrder(nativeOrder()).asXBuffer.put(Xarray) are slow

[Brian Burkhalter]

Please consider this request to accelerate absolute and relative bulk array transfer on views of heap byte buffers where the element size is greater than one. What currently happens is that the transfer devolves to a “loopy” element-by-element copy such as

        int end = offset + length;
        for (int i = offset, j = index; i < end; i++, j++)
            dst[i] = get(j);

for `get()`, and

        int end = offset + length;
        for (int i = offset, j = index; i < end; i++, j++)
            this.put(j, src[i]);

for `put()`. This is of course relatively slow.

The change proposed hoists the accelerated versions of these methods using the `ScopedMemoryAccess` methods `copyMemory()` and `copySwapMemory()` from `Direct-X-Buffer` to `X-Buffer`. The array bulk transfer methods are removed from `Direct-X-Buffer` itself. The number of lines of code in the templates decreases by 87.

With this change the throughput of array bulk `put()` and `get()` for heap view buffers is increased by a factor of 6 to 11 compared with the current code. The performance of direct view buffers does not appear to be affected.

No tests are modified or added as existing tests already cover these methods. All tests in CI tiers 1-3 passed on all platforms.

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Commit messages:
 - 8264762: ByteBuffer.byteOrder(BIG_ENDIAN).asXBuffer.put(Xarray) and ByteBuffer.byteOrder(nativeOrder()).asXBuffer.put(Xarray) are slow

Changes: https://git.openjdk.java.net/jdk/pull/3660/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3660&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264762
  Stats: 298 lines in 2 files changed: 96 ins; 183 del; 19 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3660.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3660/head:pull/3660

PR: https://git.openjdk.java.net/jdk/pull/3660