dead code removal

[Johannes Pfau via D.gnu]

Am Sun, 30 Nov 2014 01:52:57 +0000
schrieb "Mike" <none at none.com>:

> This has been brought up before:
> [1] 
> http://forum.dlang.org/post/cqzazaqxpwezignixuds@forum.dlang.org
> [2] 
> http://forum.dlang.org/post/zapxhodqmotriapuefvm@forum.dlang.org
> 
> But I'd like to know what GDC's long term plans are to enable 
> removing dead code from executables.
> 
> (1) Adding a D-specific linker script in GDC that gets 
> automagically passed to the linker?

AFAIK that's almost impossible. You can't replicate the complete linker
scripts for all architectures with all their special cases etc. It
could be possible to place all ModuleInfos in a special section then
pass a implicit linker script which extends the standard script and
only handles this section.

> (2) Adding a D-specific linker script to binutils?
> (3) LTO in GCC/binutils?

LTO is certainly a long-time (though low priority) goal. AFAIK it's
mostly about speed optimization though, not size.

> (2) sounds a little weird, but I got the impression from 
> discussion [1] that that was part of the plan.  I don't 
> understand why binutils should have to know about D's codegen, 
> but there's a lot of things I don't understand.

The linker scripts also know about some details of the C/C++ codegen.
For example attribute(constructor) needs support from linker scripts.
(KEEP, SORT_NONE, PROVIDE_HIDDEN or similar) Without this support
constructor calls would be eliminated by these optimization flags as
well. So it's kinda reasonable.

> 
> Anyway, please let me know what the plan is, and if there is 
> anything I might be able to do to move it forward.
> 
> Mike