[Patch,AVR]: Fix cc0 and loading const_int/const_double

[Denis Chertykov]

2011/11/21 Georg-Johann Lay <avr@gjlay.de>:
> After updating my local copy I get new runtime FAILs in the test suite because
> of the following sequence, e.g. from gcc.c-torture/execute/990527-1.c:
>
>        sbiw r28,1       ;  12  addhi3_clobber/1        [length = 1]
>        ldi r24,lo8(9)   ;  24  *movhi/5        [length = 2]
>        clr r25
>        brne .L3         ;  16  branch  [length = 1]
>
> The trouble is that *movhi promises that it does not change cc0. Thus, the
> correct code is:
>
>        sbiw r28,1       ;  12  addhi3_clobber/1        [length = 1]
>        ldi r24,lo8(9)   ;  24  *movhi/5        [length = 2]
>        ldi r25,0
>        brne .L3         ;  16  branch  [length = 1]
>
> The patch fixes this and adjusts cc attribute of involved insns.
>
> When loading 0, cc=none is more useful than cc=set_zn because the compiler
> knows what it loads, and cc=none preserves cc0 from preceding code.
>
> Tests pass fine again.
>
> Ok to apply?
>
> Johann
>
>        * config/avr/avr.c (output_reload_in_const): Loading a byte with 0
>        must not affect cc0.
>        * config/avr/avr.md (*movhi, *movpsi, *movsi, *movsf): Zero to any
>        register does not change cc0. Same for any constant to ld-register.
>
>

Approved.

Denis.