simplifying somewhat

src/UTF8.cs

@@ -671,16 +671,7 @@ public unsafe static (int utfadjust, int scalaradjust) calculateErrorPathadjust(
                                 contbytes += tempcont;
                             }
 
-                            // We update the continuation bytes count using just one SIMD instruction (Avx2.CompareGreaterThan).
-                            // Then we need popcount to count the number of continuation bytes and some arithmetic operations.
-                            // We use the fact that as two's complement, -65 is 0b10111111, so we can use CompareGreaterThan 
-                            // to find continuation bytes: any byte greater than -65 is a not continuation byte. E.g., the next one
-                            // is 0b11111110 (-64) and so forth. The smallest possible value is -128, which is 0b10000000.
-
-                            Vector256<sbyte> largestcont = Vector256.Create((sbyte)-65); // -65 => 0b10111111
-                            uint noncont = (uint)Avx2.MoveMask(Avx2.CompareGreaterThan(Vector256.AsSByte(currentBlock), largestcont));
-                            contbytes += (int)(32-Popcnt.PopCount(noncont));
-
+                            contbytes += (int)Popcnt.PopCount((uint)Avx2.MoveMask(byte_2_high));
                             // We use two instructions (SubtractSaturate and MoveMask) to update n4, with one arithmetic operation.
                             n4 += (int)Popcnt.PopCount((uint)Avx2.MoveMask(Avx2.SubtractSaturate(currentBlock, fourthByte)));
                         }