avx512: add basic functions to simd_utils

Extends the m512 type to use avx512 and also changes required
for limex.

src/nfa/limex_shuffle.h

@@ -62,4 +62,17 @@ u32 packedExtract256(m256 s, const m256 permute, const m256 compare) {
 }
 #endif // AVX2
 
+#if defined(HAVE_AVX512)
+static really_inline
+u32 packedExtract512(m512 s, const m512 permute, const m512 compare) {
+    // vpshufb doesn't cross lanes, so this is a bit of a cheat
+    m512 shuffled = pshufb_m512(s, permute);
+    m512 compared = and512(shuffled, compare);
+    u64a rv = ~eq512mask(compared, shuffled);
+    // stitch the lane-wise results back together
+    rv = rv >> 32 | rv;
+    return (u32)(((rv >> 16) | rv) & 0xffffU);
+}
+#endif // AVX512
+
 #endif // LIMEX_SHUFFLE_H