A.5.85 FINCSTP: Increment Floating-Point Stack Pointer
FINCSTP ; D9 F7 [8086,FPU]
FINCSTP increments the "top" field in the floating-point status word.
This has the effect of rotating the FPU register stack by one, as if
the register stack had been popped; however, unlike the popping of the
stack performed by many FPU instructions, it does not flag the new ST7
(previously ST0) as empty. See also FDECSTP (section A.5.75).