RFR: 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic [v16]

[Vladimir Ivanov]

On Thu, 26 Oct 2023 16:46:04 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> A bug in GCC causes shared libraries linked with -ffast-math to disable denormal arithmetic. This breaks Java's floating-point semantics.
>> 
>> The bug is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55522
>> 
>> One solution is to save and restore the floating-point control word around System.loadLibrary(). This isn't perfect, because some shared library might load another shared library at runtime, but it's a lot better than what we do now. 
>> 
>> However, this fix is not complete. `dlopen()` is called from many places in the JDK. I guess the best thing to do is find and wrap them all. I'd like to hear people's opinions.
>
> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove accidental include

make/test/JtregNativeHotspot.gmk line 854:

> 852:   BUILD_HOTSPOT_JTREG_EXECUTABLES_LIBS_exeFPRegs := -ldl
> 853:   BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libAsyncGetCallTraceTest := -ldl
> 854:   BUILD_HOTSPOT_JTREG_LIBRARIES_LDFLAGS_libfast-math := -ffast-math

Is the flag redundant by now? The test explicitly works with corresponding platform-specific registers.

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PR Review Comment: https://git.openjdk.org/jdk/pull/10661#discussion_r1373523640