RFR: 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic [v7]

[Vladimir Ivanov]

On Thu, 13 Oct 2022 07:47:20 GMT, Andrew Haley <aph at openjdk.org> wrote:

> The problem is that this bug is very insidious: the user probably doesn't know that there's anything wrong, and almost certainly has no idea that it's anything to do with JNI.

I'm still trying to grasp why the current problem is something different from what we experienced before.

Some platforms (x86_32 and AArch32) provide a way to restore FP environment, but it is turned off by default. Why x86_64 case is different, so it requires the logic to be turned on by default? Does the same reasoning apply to those platforms as well and we want to have `AlwaysRestoreFPU` turned on by default?    


$ grep -r AlwaysRestoreFPU src/hotspot/
src/hotspot//cpu/x86/templateInterpreterGenerator_x86.cpp:  if (AlwaysRestoreFPU) {
src/hotspot//cpu/x86/sharedRuntime_x86_32.cpp:  if (AlwaysRestoreFPU) {
src/hotspot//cpu/arm/sharedRuntime_arm.cpp:  if (AlwaysRestoreFPU) {
src/hotspot//cpu/arm/templateInterpreterGenerator_arm.cpp:  if (AlwaysRestoreFPU) {
src/hotspot//share/runtime/globals.hpp:  product(bool, AlwaysRestoreFPU, false,                                    \

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