RFR: 8283122: [AIX, s390] UnsafeCopyMemory 'Mismatched' Tests Fail on Big Endian Systems [v2]

[Tobias Hartmann]

On Mon, 14 Mar 2022 20:24:08 GMT, Tyler Steele <duke at openjdk.java.net> wrote:

>> 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.
>
> Tyler Steele has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:
> 
>   Fixes endianess-related testbug in UnsafeCopyMemory.java

Looks good to me otherwise.

test/hotspot/jtreg/compiler/unsafe/UnsafeCopyMemory.java line 28:

> 26:  * @key stress randomness
> 27:  * @library /test/lib
> 28:  * @bug 8283122

We usually don't link test bugs but the `@bug` label should be used to link (VM) bugs that have been found by that test.

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Marked as reviewed by thartmann (Reviewer).

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