On Wed, 12 Oct 2022 17:00:15 GMT, Andrew Haley <a...@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: > > 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic Thanks everyone for your contributions. I think we have a good solution: 1. Add my "fast" alternative RestoreMXCSR code, and use =1 and =2 levels of checking, as suggested by John Rose. Don't enable RestoreMXCSR by default: it should be 0 (no check). 2. Warn and restore the MXCSR at safepoints. This could be a hard error rather than a warning; not sure. At least we wouldn't have silent corruption. Everyone happy? ------------- PR: https://git.openjdk.org/jdk/pull/10661
