How to read out predicter value?

[leiwen83]

Hi,

If I want to read a predicter value in the inject code, How could I did the coding?

Thx,
Lei

[x-y-z]

You can use nvbit_read_pred_reg() to read predicate registers. Also you need to include nvbit_reg_rw.h file in your injection function file.

[liujian883]

how to index the pred reg with this api ?the general reg rw api can be set with reg index

[leiwen83]

extern "C" __device__ __noinline__ int32_t nvbit_read_pred_reg() {
#pragma unroll
    for (int i = 0; i < 32; i++) __nvbit_var += i;
    return __nvbit_var;
}

The definition of this api is as above. how to parse the result?
Like if I want to read what the current status for P5, whether it is true or not, how should I deal wtih the return value?

[x-y-z]

It reads out the entire predicate register and only the lower 8 bits ([P7 .. P0]) are used.

[leiwen83]

I try to add the code, but read out as 0...
I test it over 2080ti.

[x-y-z]

If the predicate register is not used in the code or is set to 0, the result will be 0.

[WilliamWangPeng]

I try to add the code, but read out as 0...
I test it over 2080ti.

hi dear @leiwen83
I'm also interested in this nvbit_read_pred_reg() function. but how can you display the values of this function, I try to print the values, but there is an error here,

thank you
best regards
William

[x-y-z]

It is a device function and should be called only in your instrumentation functions in the inject_func.cu file.