divmod assembly implementation

[Sam Ludacis]

On Saturday, 23 November 2024 at 21:36:23 UTC, Nick Treleaven 
wrote:
> On Saturday, 23 November 2024 at 19:54:36 UTC, Sam Ludacis 
> wrote:
>> G'day
>>
>> I'm trying to implement the Python divmod function in D w/ 
>> assembly. Should look something like this...
>>
>>     '''
>>     ulong divmod64(ulong a, ulong b, ulong quot, ulong rem)
>>     {
>>         asm {
>>             xor RDX, RDX;
>>             mov RAX, a;
>>             div b;
>>             mov quot, RAX;
>>             mov rem, RDX;
>>         }
>>     }
>>     '''
>>
>> Without doubt this routine will fail. But would anyone have a 
>> way?
>
> Just to mention that if requiring compiler optimization for 
> fast code is acceptable, you can just write it in D e.g.:
>
> ```d
> ulong[2] div(ulong a, ulong b)
> {
>     return [a / b, a % b];
> }
> ```
> ```
> $ dmd -c divmod.d -O -vasm
> _D6divmod3divFmmZG2m:
> 0000:   48 83 EC 18              sub       RSP,018h
> 0004:   48 8B C6                 mov       RAX,RSI
> 0007:   33 D2                    xor       EDX,EDX
> 0009:   48 F7 F7                 div       RDI
> 000c:   48 89 04 24              mov       [RSP],RAX
> 0010:   48 89 54 24 08           mov       8[RSP],RDX
> 0015:   48 8B 54 24 08           mov       RDX,8[RSP]
> 001a:   48 8B 04 24              mov       RAX,[RSP]
> 001e:   48 83 C4 18              add       RSP,018h
> 0022:   C3                       ret
> ```
>
> Based on an older request:
> https://forum.dlang.org/post/jd97nf$1jfj$1@digitalmars.com

Thank you