Cent/ucent why should we implement?

[Dom Disc]

On Sunday, 6 September 2026 at 10:33:15 UTC, Guillaume Piolat 
wrote:
> On Sunday, 6 September 2026 at 02:03:09 UTC, Luna wrote:
>>
>> Makes writing float/double parsers far easier given then you 
>> can assume that the compiler implements 128 bit values 
>> correctly
>
> Clock conversion in video needs 64-bit * 64-bit => 128-bit 
> result

This is already available in the registers. You just need to copy 
it out:

```d
ulong[2] mul128(const ulong u, const ulong v) @safe pure @nogc 
nothrow
{
    ulong[2] r;
    if(!u || !v) return r;
    version(D_InlineAsm_X86)
    {
       asm @trusted pure @nogc nothrow
       {
          mov R8, r.ptr;
          mov R9, v;
          mov RAX, u;
          mul R9;
          mov [R8], RAX;
          add R8,   8;
          mov [R8], RDX;
       }
    }
    else // without asm we have no access to the high bits of the 
result
    {
       // this is awfully slow (4 multiplications, 6 additions and 
8 shifts)
       // but during CTFE this will only increase the compilation 
time
       // so maybe acceptable
       enum m = uint.max;
       ulong t;
       t = (u & m)*(v & m);
       r[0] = t & m;
       t = (u>>32)*(v & m) + (t>>32);
       r[1] = t>>32;
       t = (u & m)*(v>>32) + (t & m);
       r[0] += (t<<32);
       r[1] += (u>>32)*(v>>32) + (t>>32);
    }
    return r; // r[1] contains the high bits of the product, r[0] 
the low bits (big endian)
}
```

But at least, this function should be in Phobos.