Can you shrink it further?

[Stefan Koch via Digitalmars-d]

This version has 24 instructions but these have a smaller 
encoding then and are generally inexpensive
With inline asm and conditional moves it would be possible to 
reduce this even further
to ~20 instructions.

void popFront1(ref char[] s) @trusted pure nothrow {
   immutable c = s[0];
   size_t char_length = 1;
   if (c < 127)
   {
     goto Lend;
   } else {
     if ((c & 0b1100_0000) == 0b1000_0000)
     {
       // This is invalid as a first char
       goto Lerror;
     }
     if (c < 192)
     {
       char_length = 2;
       goto Lend;
     }
     if (c < 240) {
       char_length = 3;
       goto Lend;
     }
     if (c < 248) {
        char_length = 4;
       goto Lend;
     }

     //These characters are also no longer valid
     Lerror : assert(0);
   }
   Lend :
   s = s.ptr[char_length .. s.length];
}