RFR: 8283122: [AIX, s390] UnsafeCopyMemory 'Mismatched' Tests Fail on Big Endian Systems

[Tyler Steele]

This is a testbug present on big endian systems. UnsafeCopyMemory.java contains a few tests with 'mismatched' source and destination size. These tests use Unsafe.copyMemory to copy 4 bytes between longs and ints. The location of the bytes to be copied (if the copy comes from a long), or the offset into which the bytes should be copied (if the copy is into a long) are different on big and little endian systems.

Copying from a long to int on a little endian system, the bytes to be copied are those present at the long's address.


src: _ _ _ _ | _ _ _ _
     ^ ~ ~ ^ LE copy
dst: _ _ _ _


On BE systems, the bytes are offset by 4.


src: _ _ _ _ | _ _ _ _
               ^ ~ ~ ^ BE copy
dst: _ _ _ _


The situation for copying into a long from an int is analogous.

This PR adds the required offset for the 'mismatched copy' tests. With this change, UnsafeCopyMemory.java now passes on AIX and s390.

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Commit messages:
 - Fixes endianess-related testbug in UnsafeCopyMemory.java

Changes: https://git.openjdk.java.net/jdk/pull/7811/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7811&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283122
  Stats: 12 lines in 1 file changed: 10 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7811.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7811/head:pull/7811

PR: https://git.openjdk.java.net/jdk/pull/7811