RFR(S): 8156992: [ppc] Implement template interpreter stack overflow checks as on x86/sparc.

[Lindenmaier, Goetz]

Hi Dean,

Hmm, the comment didn't really make sense before, because the field is meant
to be used in the first template Interpreter stack check, see also my explanation
in the bug: https://bugs.openjdk.java.net/browse/JDK-8156922
That's also where the MAX2 comes from:
http://hg.openjdk.java.net/jdk9/hs/hotspot/file/51d42ae63fe5/src/cpu/x86/vm/templateInterpreterGenerator_x86.cpp
line 548. The comment belongs at this place.
x86/sparc load stack_base and stack_size from thread and do some computation,
ppc only does a single load.  This is more efficient.

Also I'm not sure whether the banging can be replaced completely by
a compare, as it assures the pages are not only reserved, but really
mapped.  We had an issue quite some years before on windows, if
I remember correctly.

Best regards,
  Goetz.

From: dean.long at oracle.com [mailto:dean.long at oracle.com]
Sent: Thursday, May 19, 2016 2:15 AM
To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(S): 8156992: [ppc] Implement template interpreter stack overflow checks as on x86/sparc.

By changing the value of the _stack_overflow_limit field, does the following x86/sparc comment
still make sense?

// TODO: rather than touching all pages, check against stack_overflow_limit and bang yellow page to
// generate exception

Also, I have to admit that I don't understand why we use different values for stack checks/bang in different places, especially the using MAX2 instead of +.  Can anyone explain this?  The + makes sense to me, but the MAX2 does not.

dl
On 5/18/16 3:02 AM, Lindenmaier, Goetz wrote:

Hi,







When porting the template interpreter, we implemented a different approach to



Stack overflow handling.  See also the detailed description in the Jira bug.







This change implements the stack overflow check as on x86/sparc.



It requires simple shared changes, but only to code only used on ppc.



The changes should not affect the other platforms.







Please review this change. I please need a sponsor.



http://cr.openjdk.java.net/~goetz/wr16/8156922-ppcStackFix/webrev.01/







Best regards,



  Goetz.