RE: [avr-gcc-list] Optimiser bloats code

[Eric Weddington]

> -----Original Message-----
> From:
> address@hidden
> [mailto:address@hidden
> org] On Behalf Of Paulo Marques
> Sent: Thursday, August 02, 2007 8:13 AM
> To: address@hidden
> Subject: Re: [avr-gcc-list] Optimiser bloats code
>
> The output from gcc 4.2.0:
>
> byte inv_test(void)
> {
>          return pgm_read_byte(&inv_table[PORTB & 0x3]);
>    96:   e8 b3           in      r30, 0x18       ; 24
>    98:   ff 27           eor     r31, r31
>    9a:   e3 70           andi    r30, 0x03       ; 3
>    9c:   f0 70           andi    r31, 0x00       ; 0
>    9e:   ec 5a           subi    r30, 0xAC       ; 172
>    a0:   ff 4f           sbci    r31, 0xFF       ; 255
>    a2:   e4 91           lpm     r30, Z
> }
>    a4:   8e 2f           mov     r24, r30
>    a6:   99 27           eor     r25, r25
>    a8:   08 95           ret
>
> If not for the redundant "andi r31, 0x00" (when r31 has just

Yeah, we could really use a new peephole optimizer here...

Eric