[avr-gcc-list] Bug with -Os with constant multiplier of 3?

[David Kopf]

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>