Re: [RFC PATCH v2 4/4] target/avr/translate: Fix SBRC/SBRS instructions

[Philippe Mathieu-Daudé]

On 7/7/20 6:34 PM, Richard Henderson wrote:
> On 7/7/20 12:00 AM, Philippe Mathieu-Daudé wrote:
>> @@ -1385,7 +1385,7 @@ static bool trans_SBRC(DisasContext *ctx, arg_SBRC *a)
>>  {
>>      TCGv Rr = cpu_r[a->rr];
>>  
>> -    ctx->skip_cond = TCG_COND_EQ;
>> +    ctx->skip_cond = TCG_COND_NE;
>>      ctx->skip_var0 = tcg_temp_new();
>>      ctx->free_skip_var0 = true;
> 
> This is wrong.  The next line is
> 
>>     tcg_gen_andi_tl(ctx->skip_var0, Rr, 1 << a->bit);
> 
> So we compute "var = R & bit", which should be zero for "Skip if Bit in
> Register Clear".  Thus "var EQ 0" is the correct test.

Thanks for verifying. If TCG is correct, then some hardware register
might have a bit flipped.

I couldn't run Sarah's test suite on Fedora 30:

/usr/lib/gcc/avr/9.2.0/../../../../avr/bin/ld: cannot find
crtatmega2560.o: No such file or directory
/usr/lib/gcc/avr/9.2.0/../../../../avr/bin/ld: cannot find -lm
/usr/lib/gcc/avr/9.2.0/../../../../avr/bin/ld: cannot find -lc
/usr/lib/gcc/avr/9.2.0/../../../../avr/bin/ld: cannot find -latmega2560
collect2: error: ld returned 1 exit status

I'll try on some Debian based host.

> 
>> @@ -1401,7 +1401,7 @@ static bool trans_SBRS(DisasContext *ctx, arg_SBRS *a)
>>  {
>>      TCGv Rr = cpu_r[a->rr];
>>  
>> -    ctx->skip_cond = TCG_COND_NE;
>> +    ctx->skip_cond = TCG_COND_EQ;
>>      ctx->skip_var0 = tcg_temp_new();
>>      ctx->free_skip_var0 = true;
> 
> Similarly this is "var NE 0".