mult16x8.h

/*
Norbert Pozar 2009
http://mekonik.wordpress.com/2009/03/18/arduino-avr-gcc-multiplication/
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.*/

// 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 and stores 2 high uint8_ts
#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 uint8_ts
// rounds the number based on the MSB of the lowest uint8_t
#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"\
)