Re: [Qemu-devel] [PATCH 09/10 v11] target-tilegx: Generate tcg instructions to finish "Hello world"

[Richard Henderson <rth@twiddle.net>]

On 06/01/2015 01:54 PM, Chen Gang wrote:
>> Further, the < TILEGX_R_COUNT restriction is also incorrect.  True, you don't
>> actually implement the top 7 special registers, but that doesn't matter, you
>> should still be incrementing them.
>>
> 
> We did not implement them, so can not increment them, either.
> 
> They are hidden to outside, or we have to define and implement them.
> 
> So for me, the current code is correct.

It isn't correct, it's simply functional.  These registers may eventually be
implemented, and at that point this code will fail.  You'll note that your
store_add functions don't have the same problem, because they don't have this
R_COUNT check.  It would be better to increase the number of buffer slots and
do the right thing here in load_add.

My suggestion is to expand tmp_regs to 4, drop tmp_regcur, and have dest_gr
manage all of the indexing.  I.e.

static TCGv dest_gr(DisasContext *dc, uint8_t rdst)
{
    int n = dc->n_tmp_regs++;
    assert(n < ARRAY_SIZE(dc->tmp_regs));
    dc->tmp_regs[n].idx = rdst;
    return dc->tmp_regs[n].val = tcg_temp_new_i64();
}

In this way you can in fact call dest_gr twice within load_add and everything
will Just Work.


r~