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  1. #pragma GCC target("sse4.1")
  2. #include <iostream>
  3. #include <immintrin.h>
  4. using namespace std;
  5.  
  6. int find(int a[], int n, int x) {
  7.     __m128i needle = _mm_set_epi32(x, x, x, x);
  8.     int i = 0;
  9.     while(i+4 <= n) {
  10.         __m128i dat = _mm_load_si128(reinterpret_cast<const __m128i*>(a + i));
  11.         __m128i r = _mm_cmpeq_epi32(dat, needle);
  12.         int msk = _mm_movemask_epi8(r);
  13.         int xx = __builtin_clz(msk);
  14.         if(msk) return i + ((32 - __builtin_clz(msk)) >> 2) - 1;
  15.         i += 4;
  16.     }
  17.     while(i < n) {
  18.         if(a[i] == x) return i;
  19.         i++;
  20.     }
  21.     return -1;
  22. }
  23.  
  24. int main()
  25. {
  26.     int a[] __attribute__((aligned(16))) = {1,4, 2, 5, -10, 12, 55, 3, -4, -5};
  27.     int n = 10;
  28.     int x = -10;
  29.  
  30.     cout << find(a, n, 0) << endl;
  31.     cout << find(a, n, 1) << endl;
  32.     cout << find(a, n, 4) << endl;
  33.     cout << find(a, n, 2) << endl;
  34.     cout << find(a, n, 5) << endl;
  35.     cout << find(a, n, -10) << endl;
  36.     cout << find(a, n, 12) << endl;
  37.     cout << find(a, n, -5) << endl;
  38.  
  39.     return 0;
  40. }
  41.  
Success #stdin #stdout 0s 4484KB
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stdin
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Standard input is empty
stdout
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-1
0
1
2
3
4
5
9
https://ideone.com/9RyKeI
language:
C++ (gcc 8.3)
created:
4 years ago
visibility:
public

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