Function:

FSINCOS calculates both Sine and Cosine of an argument in ST.
The first result, sine, is stored into the original ST, destroying the
source value. The second result, cosine, is then pushed onto the stack.

Note that ST(7) must be free or an invalid operation exception may occur
because the cosine is pushed onto the stack.

The 486 bug occurs when a specific set of code is executed with a specific
set of data. There is no way you can anticipate this and the workaround
should always be implemented if code will run on a 486/487.
The bug corrupts the FPU stack without signalling it to either FPU or CPU.
Data corruption is usually the result.
Workaround: FSINCOS should always be followed by: FCLEX, FINIT, FLDCW,
FSTSW, FSTSWAX, <FSAVE> or <FSTENV> or by a WAIT
and a non-FPU instruction. Do note that some of these FPU instructions
contain bugs themselves.




FSTENV  Store Floating point Environment
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