RFR: Enable aarch64 build in jdk/tsan.

[Jie He]

On Thu, 16 Apr 2020 03:20:40 GMT, Jie He <github.com+10233373+jhe33 at openjdk.org> wrote:

>> make/autoconf/flags-cflags.m4 line 573:
>> 
>>> 572:     # Disable experimental isel due to a known issue in llvm-8, which generates wrong debug info.
>>> 573:     # (see https://bugs.llvm.org/show_bug.cgi?id=40887)
>>> 574:     if test "x$OPENJDK_TARGET_CPU" = xaarch64; then
>> 
>> Does using the latest released LLVM 10.0.0 resolve this problem? If yes, we don't need to add this flag.
>> 
>> TSAN don't have a strong fixation to LLVM 8, and we'd recommend using the latest released LLVM. Version 8 just happened
>> to be the latest released version when we wrote the wiki page. We are happy to update the Wiki page.
>
> I just tried llvm-9, the debug info is still wrong, makes debugging hard, even though the bug report said it has been
> fixed in llvm-9. after disable it by fno-experimental-isel, everything is fine.

I will take a try to use clang-10.

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PR: https://git.openjdk.java.net/tsan/pull/5