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 Some additional info to consider: the library modifies only MXCSR register and `-XX:+RestoreMXCSROnJNICalls` makes the test to pass. $ objdump -D libfast-math.so ... 0000000000000560 <set_fast_math>: 560: f3 0f 1e fa endbr64 564: 0f ae 5c 24 fc stmxcsr -0x4(%rsp) 569: 81 4c 24 fc 40 80 00 orl $0x8040,-0x4(%rsp) 570: 00 571: 0f ae 54 24 fc ldmxcsr -0x4(%rsp) 576: c3 ret ------------- PR: https://git.openjdk.org/jdk/pull/10661
