RFR: JDK-8169177 Aarch64: SIGSEGV when "-XX:+ZeroTLAB" is specified along with GC options

[Kavitha Natarajan]

Hi,

I am re-posting the review request on hotspot-dev which I had missed
earlier.

The below bug fix was already posted in aarch64-port-dev and
hotspot-compiler-dev mailing lists.

The following are the jtreg test cases that fail with SIGSEGV on aarch64
when "-XX:+ZeroTLAB" is specified along with a GC option:

hotspot/test/compiler/stringopts/TestStringObjectInitialization.java
hotspot/test/gc/TestSystemGC.java
hotspot/test/gc/arguments/TestAlignmentToUseLargePages.java
hotspot/test/gc/cms/TestBubbleUpRef.java
hotspot/test/gc/metaspace/TestMetaspacePerfCounters.java
hotspot/test/gc/parallel/TestDynShrinkHeap.java
hotspot/test/gc/stress/TestGCOld.java

Bug fix for JDK-8086053
<https://bugs.openjdk.java.net/browse/JDK-8086053> (Address
inconsistencies regarding ZeroTLAB) fixes similar issue on x86 and sparc.
This fix has been ported to aarch64 and the above test cases now pass on
aarch64 as well.

Below is the webrev for the aarch64 changes:

http://people.linaro.org/~kavitha.natarajan/8169177/webrev.00/

Derek White and Andrew Haley had done the review and suggested to use
zero_memory() only in C1 and zero_words() in C2. However, zero_words itself
need to be enhanced before its been used. So currenly zero_memory() is only
used for both C1 and C2.

A separate enhancement request has been raised for zero_words().

https://bugs.openjdk.java.net/browse/JDK-8171237

Please review and approve.

Thanks,
Kavitha