Re: [avr-gcc-list] Double 'andi' missed optimization

[eric]

> 
> I've found what looks like a missed optimization in avr-
gcc  3.3 20030512
> 
>       uint8_t Encoder;
> 
>       Encoder = (PORTD >> 4) & 12;
>    0: 82 b3           in      r24, 0x12       ; 18
>    2: 82 95           swap    r24
>    4: 8f 70           andi    r24, 0x0F       ; 15
>    6: 8c 70           andi    r24, 0x0C       ; 12
> 
> The 4 bit shift is implemented as a swap/andi , but with 
an explicit andi
> afterwards, it seems like an obvious optimization to 
combine them.
> 
> Trivial example code below, compiled with:
> avr-gcc -c e.c -g -O2 -mmcu=at90s8535 -o e.o
> 
> 
> #include <avr/io.h>
> #include <inttypes.h>
> 
> 
> int8_t        test ()
> {
> 
>       uint8_t Encoder;
> 
>       Encoder = (PORTD >> 4) & 12;
>       return(Encoder);
> 
> }
> 
> 

Please fill out a GCC bug report here: 
<http://gcc.gnu.org/bugzilla/>

Thanks
Eric