the register save must happen before the setjmp() call, which means
outside of the LUAI_TRY() macro. We also should be saving all 32
floating point registers
this fixes an issue where a lua library function triggers an exception
after it does a math operation which changes the floating point
registers on M7 MCUs (such as STM32H7). An example is math.random()
which calls math_random(), which pre-calculates a double value before
checking if the arguments to the call are valid. When it then checks
and finds invalid values the exception longjmp does not restore the
floating point registers.
Andrew Tridgell
bugobliterator
Michael du Breuil