Hi,
Using WinAVR avr-gcc 4.3.0 and 4.3.3, compiling 3*<uint8_t> with -Os calls __mulhi3 instead of the optimized *2+1 when no hardware
multiply is present. O1,O2,O3 does it right:
Target: ATTiny85
uint8_t rssi; //r24
-O1 -O2 -O3
rssi=3*rssi;
aa: 28 2f mov r18, r24
ac: 22 0f add r18, r18
ae: 28 0f add r18, r24
-Os
rssi=3*rssi;
ae: 90 e0 ldi r25, 0x00 ; 0
b0: 63 e0 ldi r22, 0x03 ; 3
b2: 70 e0 ldi r23, 0x00 ; 0
b4: 40 d0 rcall .+128 ; 0x136<__mulhi3>
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