RFR: 8247396: PCH should be disabled for opt-size feature with clang after JDK-8246751

[Erik Joelsson]

I agree with the assessment, but I think the disabling should happen in 
configure. That way the configure log can accurately tell the user why 
it was disabled. This can be done by just adding another elif in 
BPERF_SETUP_PRECOMPILED_HEADERS. To check for a jvm feature in 
configure, you can use JVM_FEATURES_IS_ACTIVE(opt-size).

/Erik

On 2020-06-11 02:25, jiefu(傅杰) wrote:
> Hi all,
>
> JBS:    https://bugs.openjdk.java.net/browse/JDK-8247396
> Webrev: http://cr.openjdk.java.net/~jiefu/8247396/webrev.00/
>
> -O3 is used for clang on MacOS after JDK-8246751.
> But it breaks the builds of VMs with opt-size feature when PCH is enabled.
>
> The reason is that the PCH was built with -Os while some other files were built with -O3, which causes an error with clang.
> It would be better to disable the PCH for opt-size builds.
>
> Thanks a lot.
> Best regards,
> Jie