On Tue, Aug 30, 2022 at 10:51:46PM +0000, ryuukk_ via Digitalmars-d wrote:
> Having this simple code makes the executable gigantic!
> 
> ```D
> struct Big
> {
>     int[1024 * 1024] big = 0;
> }
> 
> Big big;
> ```
> 
> Only with DMD, LDC produces a tiny executable
> 
> Is there a flag available to fix this behavior? it's not sustainable

Which version of dmd are you using? I tried to compile the above code with 2.098 (old git master) and the total executable size is only 900KB.

I remember about a year or two ago there was a bug where dmd would generate 1024 * 1024 store instructions to initialize the array, but I just checked the disassembly, it's now a rep stos, which is very small.


T

-- 
Life is unfair. Ask too much from it, and it may decide you don't deserve what you have now either.

On Tuesday, 30 August 2022 at 23:05:16 UTC, H. S. Teoh wrote:
> On Tue, Aug 30, 2022 at 10:51:46PM +0000, ryuukk_ via Digitalmars-d wrote:
>> Having this simple code makes the executable gigantic!
>> 
>> ```D
>> struct Big
>> {
>>     int[1024 * 1024] big = 0;
>> }
>> 
>> Big big;
>> ```
>> 
>> Only with DMD, LDC produces a tiny executable
>> 
>> Is there a flag available to fix this behavior? it's not sustainable
>
> Which version of dmd are you using? I tried to compile the above code with 2.098 (old git master) and the total executable size is only 900KB.
>
> I remember about a year or two ago there was a bug where dmd would generate 1024 * 1024 store instructions to initialize the array, but I just checked the disassembly, it's now a rep stos, which is very small.
>
>
> T

dmd --version prints: `DMD32 D Compiler v2.100.1`

It's on Windows, maybe that problem is windows specific?

On Tue, Aug 30, 2022 at 11:09:55PM +0000, ryuukk_ via Digitalmars-d wrote:
> On Tuesday, 30 August 2022 at 23:05:16 UTC, H. S. Teoh wrote:
[...]
> > Which version of dmd are you using? I tried to compile the above code with 2.098 (old git master) and the total executable size is only 900KB.
> > 
> > I remember about a year or two ago there was a bug where dmd would generate 1024 * 1024 store instructions to initialize the array, but I just checked the disassembly, it's now a rep stos, which is very small.
[...]
> dmd --version prints: `DMD32 D Compiler v2.100.1`
> 
> It's on Windows, maybe that problem is windows specific?

Possibly, Windows uses a different backend path (obviously). Try to look at the disassembly to see if it's the abovementioned problem?


T

-- 
If blunt statements had a point, they wouldn't be blunt...

On Thu, Sep 01, 2022 at 10:15:03PM +0000, solidstate1991 via Digitalmars-d wrote:
> On Tuesday, 30 August 2022 at 22:58:44 UTC, ryuukk_ wrote:
> > ```
> > $ ldc2 -m64 app.d
> > $ ll
> > total 4545
> > -rw-r--r-- 1 ryuukk 197121      69 Aug 31 00:57 app.d
> > -rwxr-xr-x 1 ryuukk 197121  453120 Aug 31 00:57 app.exe*
> > -rw-r--r-- 1 ryuukk 197121 4195865 Aug 31 00:57 app.obj
> > ```
> > 
> > ```
> > $ dmd -m64 app.d
> > $ ll
> > total 8617
> > -rw-r--r-- 1 ryuukk 197121      69 Aug 31 00:57 app.d
> > -rwxr-xr-x 1 ryuukk 197121 4623872 Aug 31 00:57 app.exe*
> > -rw-r--r-- 1 ryuukk 197121 4196322 Aug 31 00:57 app.obj
> > ```
> 
> LDC has way better optimization features, so it's kinda expected.

Yep.  LDC is my go-to compiler for release builds.  I use dmd for development because the turnaround time is faster, but I also don't care about performance/executable size when using dmd.  For release builds when I *do* care about those things, I use LDC; dmd isn't even on my radar for that.


T

-- 
Amateurs built the Ark; professionals built the Titanic.

On Thursday, 1 September 2022 at 22:31:50 UTC, H. S. Teoh wrote:
> On Thu, Sep 01, 2022 at 10:15:03PM +0000, solidstate1991 via Digitalmars-d wrote:
>> On Tuesday, 30 August 2022 at 22:58:44 UTC, ryuukk_ wrote:
>> > ```
>> > $ ldc2 -m64 app.d
>> > $ ll
>> > total 4545
>> > -rw-r--r-- 1 ryuukk 197121      69 Aug 31 00:57 app.d
>> > -rwxr-xr-x 1 ryuukk 197121  453120 Aug 31 00:57 app.exe*
>> > -rw-r--r-- 1 ryuukk 197121 4195865 Aug 31 00:57 app.obj
>> > ```
>> > 
>> > ```
>> > $ dmd -m64 app.d
>> > $ ll
>> > total 8617
>> > -rw-r--r-- 1 ryuukk 197121      69 Aug 31 00:57 app.d
>> > -rwxr-xr-x 1 ryuukk 197121 4623872 Aug 31 00:57 app.exe*
>> > -rw-r--r-- 1 ryuukk 197121 4196322 Aug 31 00:57 app.obj
>> > ```
>> 
>> LDC has way better optimization features, so it's kinda expected.
>
> Yep.  LDC is my go-to compiler for release builds.  I use dmd for development because the turnaround time is faster, but I also don't care about performance/executable size when using dmd.  For release builds when I *do* care about those things, I use LDC; dmd isn't even on my radar for that.
>
>
> T

LDC is great, but note that the object files are equally large for both compilers. Apparently it is the linker that should be attributed the size reduction. Which leads me to wonder what the main function looks like, because it might have removed the entire initialisation as dead code…

It would have been better if OP would have posted complete code.

— Bastiaan.