On Wed, 22 Feb 2023 02:08:27 GMT, Sandhya Viswanathan <sviswanat...@openjdk.org> wrote:
> Change the java/lang/float.java and the corresponding shared runtime constant > expression evaluation to generate QNaN. > The HW instructions generate QNaNs and not SNaNs for floating point > instructions. This happens across double, float, and float16 data types. The > most significant bit of mantissa is set to 1 for QNaNs. I'm also a bit concerned that we are rushing in to "fix" this. IIUC we have three mechanisms for implementing this functionality: 1. The interpreted Java code 2. The compiled non-intrinisc sharedRuntime code 3. The compiler intrinsic that uses a hardware instruction. Unless the hardware instructions for all relevant CPUs behave exactly the same, then I don't see how we can have parity of behaviour across these three mechanisms. The observed behaviour may be surprising but it seems not to be a bug. And is this even a real concern - would real programs actually need to peek at the raw bits and so see the difference, or does it suffice to handle Nan's opaquely? ------------- PR: https://git.openjdk.org/jdk/pull/12704
