Am 06.05.21 um 11:11 schrieb Павел Бельтюков: > Hi, everybody! > > Although SDCC manual contains some information about stm8 options > it has no information on working register set and procedure calling > convention. > > Can anyone explain: what registers are used and for what purpose? > > What are function call prologues and epilogues like? > > What about interrupt ? > > How parameters and return values are placed in registers/stack? > > What is the difference between medium and large memory models with > regard to previous questions? > > Best regards, > Paul Beltyukov
Current situation: * All parameters are passed on the stack. * The parameters on the stack are cleaned up by the caller (unless the callee is declared __z88dk_callee, in which case they are cleared up by the callee). * 8-Bit return values are passed in register a. * 16-Bit return values are passed in register x. * 24-Bit return values are passed in registers yl:x. * 32-Bit return values are passed in registers y:x. * For return values bigger than 32 bits, the caller passes an additional hidden parameter containing a pointer, the callee then writes the return value where that pointer points to. * For functions that needs access to more than 255 B of stack space, y is used as frame pointer. * Within the function, registers a, x and y (if not used as frame pointer) are used whichever way the register allocator decides. * Funktions declared __naked have no prologue or epilogue. * Functions declared __critical have sim / rim in prologue / epilogeu. * Function prologue consists of setting up the frame pointer, if necessary. * Functions usually return by ret (medium model) or retf (large model). Exceptions apply for some functions using __z88dk_callee. * Interrupt routines are handled like other functions (but if sdcc considers it necessary, the function prologue will contain additional code to work around hardware bug). They return by iret. Philipp _______________________________________________ Sdcc-user mailing list Sdcc-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sdcc-user
