RFR: 8253740: [PPC64] Minor interpreter cleanup

[Martin Doerr]

On Tue, 29 Sep 2020 09:12:37 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> This looks good but I also noticed that ppc and s390 pass an extra parameter to InterpreterRuntime::monitorenter() also.
>
> That's an interesting point: call_VM(monitorenter) uses check_for_exceptions=true on PPC64 and
> check_for_exceptions=false on s390. check_for_exceptions=true is default, so it's equivalent to omitting the explicit
> parameter. So PPC64 is implemented like x86 in this matter.  Seems like we have optimized the exception check out for
> s390. This should be valid because monitorenter uses JRT_ENTRY_NO_ASYNC and doesn't throw any exception. Note that the
> JIT compiler's version uses assert(!HAS_PENDING_EXCEPTION, "Should have no exception here") in
> SharedRuntime::monitor_enter_helper. (monitor_enter_helper uses the CHECK macro which does the check for an exception,
> but this looks like a bug.)  I think we could assert that in the interpreter's version and use
> check_for_exceptions=false on all platforms. It's probably not worth optimizing this, but maybe it'd be a good
> simplification wrt. complexity and readability of the gererated assembly code. At least, it'd be nice to bring the
> interpreter and the compiler version closer together. But that's a bit out of scope for this issue.

Hi David,
thanks for reminding me of JVMTI event callbacks. So we need to check s390 code.
And in SharedRuntime::monitor_enter_helper it doesn't make sense to use CHECK macro and then
assert(!HAS_PENDING_EXCEPTION, "Should have no exception here"). But this is unrelated to this PPC64 cleanup change.

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PR: https://git.openjdk.java.net/jdk/pull/385