Add support for _mm_srli_epi64

source/inteli/avx2intrin.d

@@ -3606,7 +3606,37 @@ unittest
     assert(C.array == expectedC);
 }
 
-// TODO __m256i _mm256_srli_epi64 (__m256i a, int imm8) pure @safe
+/// Shift packed 64-bit integers in `a` right by `imm8` while shifting in zeros.
+__m256i _mm256_srli_epi64 (__m256i a, int imm8) pure @safe
+{
+    static if (GDC_or_LDC_with_AVX2)
+    {
+        return cast(__m256i) __builtin_ia32_psrlqi256(cast(int8)a, cast(ubyte)imm8);
+    }
+    else 
+    {
+        // split
+        __m128i a_lo = _mm256_extractf128_si256!0(a);
+        __m128i a_hi = _mm256_extractf128_si256!1(a);
+        __m128i r_lo = _mm_srli_epi64(a_lo, imm8);
+        __m128i r_hi = _mm_srli_epi64(a_hi, imm8);
+        return _mm256_set_m128i(r_hi, r_lo);
+    }
+}
+unittest
+{
+    __m256i A = _mm256_setr_epi64(8, -4, 16, -8);
+    long4 B = cast(long4) _mm256_srli_epi64(A, 1);
+    long4 B2 = cast(long4) _mm256_srli_epi64(A, 1 + 512);
+    long[4] expectedB = [ 4, 0x7FFFFFFFFFFFFFFE, 8, 0x7FFFFFFFFFFFFFFC];
+    assert(B.array == expectedB);
+    assert(B2.array == expectedB);
+
+    long4 C = cast(long4) _mm256_srli_epi64(A, 64);
+    long[4] expectedC = [ 0, 0, 0, 0 ];
+    assert(C.array == expectedC);
+}
+
 // TODO __m256i _mm256_srli_si256 (__m256i a, const int imm8) pure @safe
 // TODO __m128i _mm_srlv_epi32 (__m128i a, __m128i count) pure @safe
 // TODO __m256i _mm256_srlv_epi32 (__m256i a, __m256i count) pure @safe