• bearophile (7/7) May 20 2014 Instead (or in addition) of this dmd compiler switch:
• Meta (5/12) May 20 2014 I think I remember Adam Ruppe mentioning somewhere that you can
• bearophile (4/8) May 20 2014 Then why is -vgc includes among the dmd switches?
• Adam D. Ruppe (5/6) May 20 2014 Yeah, it will work, but it isn't as convenient as a compiler
• David Nadlinger (7/12) May 20 2014 No. There are quite a few runtime functions which don't in fact
• bearophile (5/7) May 20 2014 Finding them is the point of a "-noruntime" switch. Now for just
• bearophile (38/38) May 21 2014 This shows one purpose of the ldc2 -noruntime switch. A simple

"bearophile" <bearophileHUGS lycos.com> writes:

Instead (or in addition) of this dmd compiler switch:

-vgc           list all hidden gc allocations

Isn't it more useful a compiler switch like "-noruntime" (similar 
to the switch of the ldc2 compiler) meant to list the lines of 
code where are implicit calls to runtime funcitions?

Bye,
bearophile

"Meta" <jared771 gmail.com> writes:

On Tuesday, 20 May 2014 at 10:39:32 UTC, bearophile wrote:
 Instead (or in addition) of this dmd compiler switch:

 -vgc           list all hidden gc allocations

 Isn't it more useful a compiler switch like "-noruntime" 
 (similar to the switch of the ldc2 compiler) meant to list the 
 lines of code where are implicit calls to runtime funcitions?

 Bye,
 bearophile

I think I remember Adam Ruppe mentioning somewhere that you can 
use a custom object.d and omit the Druntime functions, and the 
linker will complain about them at link-time where they're used. 
That more or less does the trick, doesn't it?

"bearophile" <bearophileHUGS lycos.com> writes:

Meta:

 I think I remember Adam Ruppe mentioning somewhere that you can 
 use a custom object.d and omit the Druntime functions, and the 
 linker will complain about them at link-time where they're 
 used. That more or less does the trick, doesn't it?

Then why is -vgc includes among the dmd switches?

Bye,
bearophile

"Adam D. Ruppe" <destructionator gmail.com> writes:

On Tuesday, 20 May 2014 at 15:53:51 UTC, Meta wrote:
 That more or less does the trick, doesn't it?

Yeah, it will work, but it isn't as convenient as a compiler 
helper thingy because pulling a function out of object.d can be a 
pain and the linker error isn't as easy to read as a compiler 
error (no code line number for example).

"David Nadlinger" <code klickverbot.at> writes:

On Tuesday, 20 May 2014 at 10:39:32 UTC, bearophile wrote:
 Instead (or in addition) of this dmd compiler switch:

 -vgc           list all hidden gc allocations

 Isn't it more useful a compiler switch like "-noruntime" 
 (similar to the switch of the ldc2 compiler) meant to list the 
 lines of code where are implicit calls to runtime funcitions?

No. There are quite a few runtime functions which don't in fact 
allocate. -vgc is a tool to help in avoiding GC allocations, not 
all druntime dependencies.

I'd suspect that the answer to the question about the "more 
useful" behavior depends entirely on your use case.

David

"bearophile" <bearophileHUGS lycos.com> writes:

David Nadlinger:

 There are quite a few runtime functions which don't in fact 
 allocate.

Finding them is the point of a "-noruntime" switch. Now for just 
the ones that allocate we have  nogc.

Bye,
bearophile

"bearophile" <bearophileHUGS lycos.com> writes:

This shows one purpose of the ldc2 -noruntime switch. A simple 
test program:


void foo(ref int[10] data) {
     data[0 .. 3] = 5;
     data[7 .. 9] = 10;
}
void main() {}


dmd compiles it to:

_D5test53fooFKG10iZv:
L0:     push    EAX
         push    3
         push    5
         push    EAX
         call    near ptr __memset32
         push    2
         push    0Ah
         mov EAX,014h[ESP]
         lea ECX,01Ch[EAX]
         push    ECX
         call    near ptr __memset32
         add ESP,018h
         pop EAX
         ret


ldc2 is smarter and removes the calls to memset, generating kind 
of optimal 32 bit code:

__D5test53fooFKG10iZv:
     movl    $5, (%eax)
     movl    $5, 4(%eax)
     movl    $5, 8(%eax)
     movl    $10, 28(%eax)
     movl    $10, 32(%eax)
     ret

If you call such function many times you see a significant run 
time difference between the two compilations.

A switch like -noruntime helps find the unwanted cases where the 
compiler you are using doesn't remove some run time call.

Bye,
bearophile