Tune AVX512 code

kimwalisch · Jun 19, 2024 · af7700e · af7700e
1 parent f307dd8
commit af7700e
Showing 1 changed file with 9 additions and 5 deletions.
diff --git a/include/Sieve.hpp b/include/Sieve.hpp
@@ -208,14 +208,18 @@ class Sieve
       // Compute this for loop using AVX512.
       // for (i = start_idx + 1; i < stop_idx; i++)
       //   cnt += popcnt64(sieve64[i]);
-      do {
-        __mmask8 mask = (i + 8 < stop_idx) ? 0xff : (__mmask8) _bzhi_u64(0xff, stop_idx - i);
-        __m512i vec = _mm512_maskz_loadu_epi64(mask , &sieve64[i]);
+      //
+      for (; i + 8 < stop_idx; i += 8)
+      {
+        __m512i vec = _mm512_loadu_epi64(&sieve64[i]);
         vec = _mm512_popcnt_epi64(vec);
         vcnt = _mm512_add_epi64(vcnt, vec);
-        i += 8;
       }
-      while (i < stop_idx);
+
+      __mmask8 mask = (__mmask8) _bzhi_u64(0xff, stop_idx - i);
+      __m512i vec = _mm512_maskz_loadu_epi64(mask , &sieve64[i]);
+      vec = _mm512_popcnt_epi64(vec);
+      vcnt = _mm512_add_epi64(vcnt, vec);
 
       cnt += _mm512_reduce_add_epi64(vcnt);
       cnt += popcnt64(sieve64[stop_idx] & m2);