RFR: Enable aarch64 build in jdk/tsan.

[Man Cao]

On Wed, 15 Apr 2020 08:46:30 GMT, Jie He <github.com+10233373+jhe33 at openjdk.org> wrote:

> Enable INCLUDE_TSAN in aarch64, and add the option -fno-experiment-isel when build aarch64 to
> avoid a known bug [1] in llvm-8, recommended compiler in jdk/tsan,
> which generates wrong debug info.
> 
> In addition, change aarch64 release build option from -O3 to -Os to prevent a crash occurs
> in build process, caused by a known issue [2].
> 
> [1] https://bugs.llvm.org/show_bug.cgi?id=40887
> [2] https://bugs.llvm.org/show_bug.cgi?id=44581

I have also sent Skara a question about "/covered" command and OCA.
https://mail.openjdk.java.net/pipermail/skara-dev/2020-April/002375.html

make/autoconf/flags-cflags.m4 line 303:

> 302:     # (see https://bugs.llvm.org/show_bug.cgi?id=44581) which makes release build crash in aarch64.
> 303:     if test "x$OPENJDK_TARGET_OS" = xmacosx || test "x$OPENJDK_TARGET_CPU" = xaarch64; then
> 304:       # On MacOSX we optimize for size, something

Would you consider contributing this change to jdk/jdk mainline?

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.

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