On 5/20/25 1:56 PM, Robin Dapp wrote:
Maybe I'm missing something there. Particularly whether or not you
can know anything about frm's value after a call has returned.
Normally the answer to this kind of question is a hard no.
AFAICT the main difference to standard mode switching is that we (ab)use
it to set the rounding mode to the value it had initially, either at
function entry or after a call. That's different to regular mode
switching which assumes "static" rounding modes for different instructions.
Standard could e.g. be:
- insn1 demands frm1
- call1 demands frm4
- call2 demands frm5
Whereas we have:
- insn1 demands frm1
- call1 demands "frm at the start of the function"
- call2 demands "frm after call1 that could have called fesetround"
Weird, call2 can demand the frm as it existed after call1?!? I'm going
to try not to cry and return to my bubble :-)
Jeff
