RFR: 8255579: x86: Use cmpq(Register, Address) in safepoint_poll [v2]

[Erik Österlund]

On Thu, 29 Oct 2020 10:08:58 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> JDK-8253180 added a new block in `safepoint_poll` that uses broken `cmpq` (JDK-8255550): it effectively does the comparison with operands swapped. It makes sense to use the non-broken `cmpq`, as to avoid changing the condition code and thus making the code less understandable. See the discussion in #910. 
>> 
>> Testing:
>>   - [x] `tier1` with Z (some SA tests fail, and some other fail with OOME -- seem to be expected/problem-listed)
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8255579-safepoint-poll
>  - 8255579: x86: Use cmpq(Register,Address) in safepoint_poll

Marked as reviewed by eosterlund (Reviewer).

-------------

PR: https://git.openjdk.java.net/jdk/pull/924