digitalmars.D.learn - divmod assembly implementation
- Sam Ludacis (16/16) Nov 23 G'day
- Nick Treleaven (25/42) Nov 23 Just to mention that if requiring compiler optimization for fast
- Sam Ludacis (3/49) Nov 23 Thank you
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?
Nov 23
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
Nov 23
Sam Ludacis <samludacis mail.com> 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:Thank youG'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
Nov 23