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

[Daniel D. Daugherty]

On Tue, 11 Oct 2022 16:02:41 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.

It seems strange to me that the native library part is here:

test/hotspot/jtreg/runtime/jni/TestDenormalFloat/libfast-math.c

and the two test files are here:

test/hotspot/jtreg/compiler/floatingpoint/TestDenormalDouble.java
test/hotspot/jtreg/compiler/floatingpoint/TestDenormalFloat.java

And the two tests don't have "@run main/native"... Maybe I'm missing
something about what you're trying to test here.

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PR: https://git.openjdk.org/jdk/pull/10661