Re: [Qemu-devel] Adding a parameter to a helper

[Jose Cano Reyes <jcano@ac.upc.edu>]

Many thanks for your response Laurent.


- So, how ca I obtain the value that TCGv_i32 represents?

- I don't understand well how a helper functions. For instance, 
cosidering this call to a helper again:

         gen_helper_flds_ST0(cpu_tmp2_i32, tcg_const_i32(MY_INT_VALUE))

   Can I obtain the parameters "cpu_tmp2_i32" and 
"tcg_const_i32(MY_INT_VALUE)" from the args[0] and args[1] described in 
DEF_HELPER_FLAGS_2???


Jose.



El 31/07/12 15:19, Laurent Desnogues escribió:
> On Mon, Jul 30, 2012 at 6:40 PM, Jose Cano Reyes <jcano@ac.upc.edu> wrote:
>> I am trying to add a new integer parameter to an existing helper and call
>> this helper in "targeti386/translate.c". I have several problems:
>>
>> 1) I cannot add an integer parameter to the helper, the compiler says that
>> it must be "TCGv_i32", despite I declare this new parameter as "int" in
>> "target-i386/helper.h". Why?
> Helpers only accept TCGv parameters.
>
>> 2) If I use the the function "tcg_const_i32" in order to convert my integer
>> to TCGv_i32 I always obtain the same output value, that is:
>>
>>          tcg_const_i32(10) = 1074260520
>>          tcg_const_i32(22) = 1074260520
>>          tcg_const_i32(30) = 1074260520
>>          ...
> TCGv is an index, not the value it represents.  Think of it
> as an id.
>
> tcg_const will allocate a TCGv and then emit a TCG mov
> instruction to assign it a value.
>
>> 3) Moreover, wen I pass this value in the helper call "gen_helper_flds_ST0",
>> that is:
>>
>>       gen_helper_flds_ST0(cpu_tmp2_i32, tcg_const_i32(MY_INT_VALUE));
>>
>>      How can I use MY_INT_VALUE later in the function "tcg_gen_helperN" .
>> This function is called by DEF_HELPER_FLAGS2, which corresponds to
>> DEF_HELPER_2 (definition of my helper).
> Look at helper_aam, that should help :-)
>
>
> Laurent