millfork/include/i80_math.mfk

#if not(ARCH_I80)
#warn i80_math module should be used only on 8080-like targets
#endif

#pragma zilog_syntax

#if CPUFEATURE_Z80 || CPUFEATURE_GAMEBOY

inline asm byte __mul_u8u8u8() {
    ? LD E,A
    ? LD A, 0
    ? JR __mul_u8u8u8_start
    __mul_u8u8u8_add:
    ? ADD A,E
    __mul_u8u8u8_loop:
    ? SLA E
    __mul_u8u8u8_start:
    ? SRL D
    ? JR C, __mul_u8u8u8_add
    ? JR NZ, __mul_u8u8u8_loop
    ? RET
}

#else

inline asm byte __mul_u8u8u8() {
    ? LD E,A
    ? LD C, 0
    ? JP __mul_u8u8u8_start
    __mul_u8u8u8_add:
    ? LD A,C
    ? ADD A,E
    ? LD C,A
    __mul_u8u8u8_loop:
    ? LD A,E
    ? ADD A,A
    ? LD E,A
    __mul_u8u8u8_start:
    ? OR A
    ? LD A,D
    ? RRA
    ? LD D,A
    ? JP C, __mul_u8u8u8_add
    ? OR A
    ? JP NZ, __mul_u8u8u8_loop
    ? LD A,C
    ? RET
}

#endif