// guest openmusiclabs 6.8.11
// taken from http://mekonik.wordpress.com/2009/03/18/arduino-avr-gcc-multiplication/
// added MultiSU16XConst8toH16
// although the constant multiplies arent any faster
// than just creating a local variable equal to your constant
// added MultiU16x8toH16

// multiplies 16 bit X 8 bit
// stores lower 16 bits
#define MultiSU16X8toL16(intRes, int16In, int8In) \
asm volatile ( \
"mul %A1, %2 \n\t"\
"movw %A0, r0 \n\t"\
"mulsu %B1, %2 \n\t"\
"add %B0, r0 \n\t"\
"clr r1"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"a" (int8In) \
)

// multiplies 16 bit number X 8 bit constant
// saves lower 16 bit
// 8 cycles
#define MultiSU16XConst8toL16(intRes, int16In, int8In) \
asm volatile ( \
"ldi r22, %2 \n\t"\
"mul %A1, r22 \n\t"\
"movw %A0, r0 \n\t"\
"mulsu %B1, r22 \n\t"\
"add %B0, r0 \n\t"\
"clr r1 \n\t"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"M" (int8In) \
:\
"r22"\
)

// multiplies 16 bit number X 8 bit constant
// saves higher 16 bit
// 8 cycles
#define MultiSU16XConst8toH16(intRes, int16In, int8In) \
asm volatile ( \
"clr r26 \n\t"\
"ldi r22, %2 \n\t"\
"mulsu %B1, r22 \n\t"\
"movw %A0, r0 \n\t"\
"mul %A1, r22 \n\t"\
"add %A0, r1 \n\t"\
"adc %B0, r26 \n\t"\
"clr r1 \n\t"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"M" (int8In) \
:\
"r22", \
"r26"\
)

// multiplies 16 bit number X 8 bit and stores 2 high bytes
#define MultiSU16X8toH16(intRes, int16In, int8In) \
asm volatile ( \
"clr r26 \n\t"\
"mulsu %B1, %A2 \n\t"\
"movw %A0, r0 \n\t"\
"mul %A1, %A2 \n\t"\
"add %A0, r1 \n\t"\
"adc %B0, r26 \n\t"\
"clr r1 \n\t"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"a" (int8In) \
:\
"r26"\
)

// multiplies 16 bit signed number X 8 bit and stores 2 high bytes
// rounds the number based on the MSB of the lowest byte
#define MultiSU16X8toH16Round(intRes, int16In, int8In) \
asm volatile ( \
"clr r26 \n\t"\
"mulsu %B1, %A2 \n\t"\
"movw %A0, r0 \n\t"\
"mul %A1, %A2 \n\t"\
"add %A0, r1 \n\t"\
"adc %B0, r26 \n\t"\
"lsl r0 \n\t"\
"adc %A0, r26 \n\t"\
"adc %B0, r26 \n\t"\
"clr r1 \n\t"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"a" (int8In) \
:\
"r26"\
)

// multiplies 16 bit number X 8 bit and stores 2 high bytes
#define MultiU16X8toH16(intRes, int16In, int8In) \
asm volatile ( \
"clr r26 \n\t"\
"mul %B1, %A2 \n\t"\
"movw %A0, r0 \n\t"\
"mul %A1, %A2 \n\t"\
"add %A0, r1 \n\t"\
"adc %B0, r26 \n\t"\
"clr r1 \n\t"\
: \
"=&r" (intRes) \
: \
"a" (int16In), \
"a" (int8In) \
:\
"r26"\
)