Dead Code Elimination

[Walter Bright]

On 10/18/2026 11:45 PM, Richard (Rikki) Andrew Cattermole wrote:
> On 19/10/2026 7:36 PM, Walter Bright wrote:
>> On 10/18/2026 8:33 AM, libxmoc wrote:
>>> I noticed that dmd doesn't do DCE
>>
>> Yes, it does. Use the -O switch.
> 
> dmd -O
> 
> ```d
> void main() {
> 
> }
> 
> void foo() {
> }
> ```
> 
> ```asm.text._Dmain    segment
>      assume    CS:.text._Dmain
> _Dmain:
>          push    RBP
>          mov    RBP,RSP
>          xor    EAX,EAX
>          pop    RBP
>          ret
> .text._Dmain    ends
> .text.void onlineapp.foo()    segment
>      assume    CS:.text.void onlineapp.foo()
> void onlineapp.foo():
>          push    RBP
>          mov    RBP,RSP
>          pop    RBP
>          ret
>          add    [RAX],AL
> .text.void onlineapp.foo()    ends
> ```


Current version of dmd:

_Dmain:
0000:   31 C0                    xor       EAX,EAX
0002:   C3                       ret
_D4dead3fooFZv:
0000:   C3                       ret