8247396: PCH should be disabled for opt-size feature with clang after JDK-8246751(Internet mail)

[jiefu(傅杰)]

Hi Magnus,

Thanks for your review and valuable comments.

I've tested with clang and gcc on linux/x64.
gcc seems to be fine.
The bug can be reproduced only when clang was used.

Best regards,
Jie

On 2020/6/11, 9:42 PM, "Magnus Ihse Bursie" <magnus.ihse.bursie at oracle.com> wrote:

    On 2020-06-11 14:34, Erik Joelsson wrote:
    > 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).
    Actually, I'm not sure I agree with the assessment. Why does this only 
    happen for clang? Is it a problem when building with opt-size and pch 
    for other compilers?
    
    If not, that's likely due to the problematic files being excluded from 
    PCH (if I remember correctly). I believe a better way forward would be 
    to make sure that files that are compiled with a different optimization 
    level should be excluded from PCH for clang as well.
    
    /Magnus
    >
    > /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