Pack high bit of every byte in ARM NEON, for 64 bytes like AVX512 vpmovb2m?

__builtin_ia32_cvtb2mask512() is the GNU C builtin for vpmovb2m k, zmm.
The Intel intrinsic for it is _mm512_movepi8_mask.

It extracts the most-significant bit from each byte, producing an integer mask.

The SSE2 and AVX2 instructions pmovmskb and vpmovmskb do the same thing for 16 or 32-byte vectors, producing the mask in a GPR instead of an AVX-512 mask register. (_mm_movemask_epi8 and _mm256_movemask_epi8).

1. I would like an implementation for ARM that is faster than below
2. I would like an implementation for ARM NEON
3. I would like an implementation for ARM SVE

I have attached a basic scalar implementation in C. For those trying to implement this in ARM, we care about the high bit, but each byte's high bit (in a 128bit vector), can be easily shifted to the low bit using the ARM NEON intrinsic: vshrq_n_u8(). Note that I would prefer not to store the bitmap to memory, it should just be the return value of the function similar to the following function.

#define _(n) __attribute((vector_size(1<<n),aligned(1)))
typedef char V  _(6); // 64 bytes, 512 bits
typedef unsigned long U;
#undef _
U generic_cvtb2mask512(V v) {
   U mask=0;int i=0; 
   while(i<64){
     // shift mask by 1 and OR with MSB of v[i] byte
     mask=(mask<<1)|((v[i]&0x80)>>7);
     i++;}
   return mask;
}

This is one possible algorithm for 16 bytes (128b vector), it would just need to be put into a loop for 64 bytes (512b vector):

#define _(n) __attribute((vector_size(1<<n),aligned(1)))
typedef char g4 _(4); // 16 bytes, 128 bits
typedef char g3 _(3); // 8 bytes,   64 bits
typedef unsigned long U;
#undef _

unsigned short get_16msb(g4 v) {
  unsigned short = ret;

  // per byte, make every bit same as msb
  g4 msb = vdupq_n_u8(0x80);
  g4 filled = vceqq_u8(v, msb);

  // create a mask of each bit value
  g4 b = {0x80, 0x40, 0x20, 0x01, 0x08, 0x04, 0x02, 0x01,
          0x80, 0x40, 0x20, 0x01, 0x08, 0x04, 0x02, 0x01};

  // and vectors together
  g4 z = vandq_u8 (filled,b);

  // extract lower 8 bytes, hi 8 bytes
  g3 lo = vget_low_u8(z);
  g3 hi = vget_high_u8(z);

  // 'or' the 8 bytes of lo together ...
  // put in byte 1 of ret
  // 'or' the 8 bytes of hi together ...  
  // put in byte 2 of ret

  return ret;
}