Can you shrink it further?

[Stefan Koch via Digitalmars-d]

On Monday, 10 October 2016 at 15:17:05 UTC, Stefan Koch wrote:
> On Monday, 10 October 2016 at 03:55:17 UTC, Andrei Alexandrescu 
> wrote:
>>
>> Oh, forgot to mention: the initial/short path should only 
>> check for ASCII, i.e. c < 0x80. -- Andrei

Since in this case stability of min is concern, you can shave of 
another 2 instructions by writing the comparison by hand

void popFront1(ref char[] s) @trusted pure nothrow {
   immutable c = s[0];
   size_t char_length = 1;
   if (!(c & 0x80)) {
     goto Lend;
   } else {
     import core.bitop;
     uint i = 7u - bsr(~c | 1u);
     import std.algorithm;
     if (i > 6u) goto Lend;
     char_length = i < s.length ? i : s.length;
   }
   Lend :
   s = s.ptr[char_length .. s.length];
}