Re: [Qemu-devel] [PATCH v8 08/16] target-or32: Add instruction translation

[Blue Swirl]

On Wed, Jul 4, 2012 at 11:59 PM, Jia Liu <address@hidden> wrote:
> On Wed, Jul 4, 2012 at 10:23 AM, Jia Liu <address@hidden> wrote:
>> Hi Blue,
>>
>> On Wed, Jul 4, 2012 at 2:48 AM, Blue Swirl <address@hidden> wrote:
>>> On Sun, Jul 1, 2012 at 2:45 AM, Jia Liu <address@hidden> wrote:
>>>> +    switch (op0) {
>>>> +    case 0x00:    /* l.j */
>>>> +        LOG_DIS("l.j %d\n", N26);
>>>> +    case 0x01:    /* l.jal */
>>>> +        LOG_DIS("l.jal %d\n", N26);
>>>> +    case 0x03:    /* l.bnf */
>>>> +        LOG_DIS("l.bnf %d\n", N26);
>>>> +    case 0x04:    /* l.bf */
>>>> +        LOG_DIS("l.bf %d\n", N26);
>>>> +
>>>> +        gen_jump(dc, N26, 0, op0);
>>>
>>> The cases 0x00 to 0x03 will fall through to this case, calling LOG_DIS
>>> one to four times.
>>
>> Sorry, I can't find a better path. Is this code OK?
>>
>>     switch (op0) {
>>     case 0x00:    /* l.j */
>>     case 0x01:    /* l.jal */
>>     case 0x03:    /* l.bnf */
>>     case 0x04:    /* l.bf */
>>         LOG_DIS("l.j/l.jal/l.bnf/l.bf %d\n", N26);
>>
>>         gen_jump(dc, N26, 0, op0);
>>
>
> or is this code OK?
>
>     switch (op0) {
>     case 0x00:    /* l.j */
>         LOG_DIS("l.j %d\n", N26);
>         gen_jump(dc, N26, 0, op0);
>         break;
>     case 0x01:    /* l.jal */
>         LOG_DIS("l.jal %d\n", N26);
>         gen_jump(dc, N26, 0, op0);
>         break;
>     case 0x03:    /* l.bnf */
>         LOG_DIS("l.bnf %d\n", N26);
>         gen_jump(dc, N26, 0, op0);
>         break;
>     case 0x04:    /* l.bf */
>         LOG_DIS("l.bf %d\n", N26);
>         gen_jump(dc, N26, 0, op0);
>         break;

Yes, with N26 defined only when LOG_DIS does something (see below).

>
>
>>>> +
>>>> +    case 0x11:    /* l.jr */
>>>> +        LOG_DIS("l.jr r%d\n", rb);
>>>> +    case 0x12:    /* l.jalr */
>>>> +        LOG_DIS("l.jalr r%d\n", rb);
>>>> +
>>>> +        gen_jump(dc, 0, rb, op0);
>>>
>>> Also here.
>>>
>>
>> And, this?
>>
>      case 0x11:    /* l.jr */

Now there's no LOG_DIS() line.

>          gen_jump(dc, 0, rb, op0);
>          break;
>      case 0x12:    /* l.jalr */
>          LOG_DIS("l.jr r%d\n", rb);
>          gen_jump(dc, 0, rb, op0);
>          break;
>
>>>> +static void dec_sys(DisasContext *dc, uint32_t insn)
>>>> +{
>>>> +    uint32_t op0;
>>>> +    /*uint32_t K16;*/
>>>> +    op0 = field(insn, 16, 8);
>>>> +    /*K16 = field(insn, 0, 16);*/
>>>> +
>>>> +    switch (op0) {
>>>> +    case 0x000:    /* l.sys */
>>>> +        /*LOG_DIS("l.sys %d\n", K16);*/
>>>
>>> Why commented out?
>>
>> When I build QEMU, I got a error msg like "unused var K16, treat
>> warnings as errors".
>> I didn't find a better way to handle it, so, commented it.

This can be avoided by adjusting those variable definitions which are
only used by LOG_DIS() so that they are only defined when LOG_DIS
needs them:
#ifdef OPENRISC_DISAS
  int K16, N26;
#endif

>>
>>>
>>>> +        tcg_gen_movi_tl(cpu_pc, dc->pc);
>>>> +        gen_exception(dc, EXCP_SYSCALL);
>>>> +        dc->is_jmp = DISAS_UPDATE;
>>>> +        break;
>>>> +
>>>> +    case 0x100:    /* l.trap */
>>>> +        /*LOG_DIS("l.trap %d\n", K16);*/
>>>
>>> Ditto
>>>
>>
>> And, commented it here.
>>
>>>> +        tcg_gen_movi_tl(cpu_pc, dc->pc);
>>>> +        gen_exception(dc, EXCP_TRAP);
>>>> +        break;
>>>> +
>>
>> Regards,
>> Jia.
>
>
> Regards,
> Jia.