The pragma you want is

EXCLUDE NONE | {acc[,b[,dpl[,dph]]] - The exclude pragma disables generation of pair of push/pop instruction in ISR function (using interrupt keyword). The directive should be placed immediately before the ISR function definition and it affects ALL ISR functions following it. To enable the normal register saving for ISR functions use #pragma EXCLUDE none.
I use the s51 simulator It has some unsupported bits:sleep mode doesnt work and the serial port always runs with timer1 in mode 1
apart from that is pretty stable.
available from http://mazsoli.iit.uni-miskolc.hu/~drdani/e...bedded/s51