x86 - _mm256_testz_pd not working? -


i'm working on core i7 on linux , using g++ 4.63.

i tried following code:

#include <iostream> #include <immintrin.h>  int main() { __m256d = _mm256_set_pd(1,2,3,4); __m256d z = _mm256_setzero_pd(); std::cout << _mm256_testz_pd(a,a) << std::endl; std::cout << _mm256_testz_pd(z,z) << std::endl; std::cout << _mm256_testz_pd(a,z) << std::endl; }

it printed 3 1's. expecting @ least 1 of them 0.

i tried using _mm256_castpd_si256 , _mm256_testz_si256, it'll print 0 first line.

why?

whereas _mm256_testz_si256 (vptest) operates on bits in source vectors, _mm256_testz_pd (vtestpd) operates on sign bit of each double precision element. in test sign bits in both vectors zero, you're getting correct result.


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