Is cross-module-inlining enabled by default in LDC when compiling in release mode or do I have to use explicitly flag for it? I can't find any such flag from the output of neither

    ldc2 -h

nor

    ldmd2 -h

.

Johan Engelen mentioned this, then experimental, flag in his DConf talk from 2017 [1]

[1] https://www.youtube.com/watch?v=IZY67TBZ0V4

On Sunday, 9 August 2020 at 22:18:13 UTC, Per Nordlöw wrote:
> Is cross-module-inlining enabled by default in LDC when compiling in release mode or do I have to use explicitly flag for it? I can't find any such flag from the output of neither
>
>     ldc2 -h
>
> nor
>
>     ldmd2 -h
>
> .
>
> Johan Engelen mentioned this, then experimental, flag in his DConf talk from 2017 [1]
>
> [1] https://www.youtube.com/watch?v=IZY67TBZ0V4

If you enable link time optimisation you get cross module inlining,

-flto=full

I'm not 100% sure but I think LDC did cross module inlining by default at some point, then I updated the compiler and had to add the LTO thing. I think there is an option to enable just cross module inlining, but if you want speed you'll probably want to have LTO enabled anyway?

On Sunday, 9 August 2020 at 22:45:16 UTC, claptrap wrote:
> I'm not 100% sure but I think LDC did cross module inlining by default at some point, then I updated the compiler and had to add the LTO thing. I think there is an option to enable just cross module inlining, but if you want speed you'll probably want to have LTO enabled anyway?

Yes, I do. Thanks.

On Mon, Aug 10, 2020 at 12:20 AM Per Nordlöw via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote:
>
> Is cross-module-inlining enabled by default in LDC when compiling in release mode or do I have to use explicitly flag for it? I can't find any such flag from the output of neither
>
>      ldc2 -h
>
> nor
>
>      ldmd2 -h
>
> Johan Engelen mentioned this, then experimental, flag in his DConf talk from 2017 [1]
>
> [1] https://www.youtube.com/watch?v=IZY67TBZ0V4

ldc2 --help-hidden | grep cross
  --disable-demotion                                              - Clone
multicolor basic blocks but do not demote cross scopes
 * --enable-cross-module-inlining=<value>                          - (*)
Enable cross-module function inlining (default disabled)*
  --iterative-counter-promotion                                   - Allow
counter promotion across the whole loop nest.
  --jump-threading-across-loop-headers                            - Allow
JumpThreading to thread across loop headers, for testing
  --licm-n2-threshold=<int>                                       - How
many instruction to cross product using AA
  --lsr-backedge-indexing                                         - Enable
the generation of cross iteration indexed memops
    =cross-dso-cfi                                                -
Cross-DSO CFI
    =cross-dso-cfi                                                -
Cross-DSO CFI
  --split-dwarf-cross-cu-references                               - Enable
cross-cu references in DWO files
  --x86-align-branch-boundary=<uint

On Mon, Aug 10, 2020 at 12:50 AM claptrap via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote:

> On Sunday, 9 August 2020 at 22:18:13 UTC, Per Nordlöw wrote:
> > ...
> If you enable link time optimisation you get cross module inlining,
>
> -flto=full
>
> I'm not 100% sure but I think LDC did cross module inlining by default at some point, then I updated the compiler and had to add the LTO thing. I think there is an option to enable just cross module inlining, but if you want speed you'll probably want to have LTO enabled anyway?
>

I am not sure but last time I checked ldc does not do cross module inlinig by default, and LTO only help if your ldc(druntime+phobos) are built with enabled LTO[1]

[1] https://github.com/ldc-developers/ldc/issues/2182#issuecomment-343166633

On Monday, 10 August 2020 at 05:54:14 UTC, Daniel Kozak wrote:
> I am not sure but last time I checked ldc does not do cross module inlinig by default, and LTO only help if your ldc(druntime+phobos) are built with enabled LTO[1]
>
> [1] https://github.com/ldc-developers/ldc/issues/2182#issuecomment-343166633

Are the official LDC-releases builtin with or without LTO?

On Mon, Aug 10, 2020 at 1:15 PM Per Nordlöw via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote:

> On Monday, 10 August 2020 at 05:54:14 UTC, Daniel Kozak wrote:
> > I am not sure but last time I checked ldc does not do cross module inlinig by default, and LTO only help if your ldc(druntime+phobos) are built with enabled LTO[1]
> >
> > [1] https://github.com/ldc-developers/ldc/issues/2182#issuecomment-343166633
>
> Are the official LDC-releases builtin with or without LTO?
>

AFAIK only for OSX, but Arch linux ldc package is now build with  LTO enabled

On Monday, 10 August 2020 at 11:11:57 UTC, Per Nordlöw wrote:
> Are the official LDC-releases builtin with or without LTO?

Most of them are, but not sure why that matters here (the gain is almost negligible and mainly interesting for the C++ parts - as all D files are compiled to a single object file anyway).

> On Monday, 10 August 2020 at 05:54:14 UTC, Daniel Kozak wrote:
>> I am not sure but last time I checked ldc does not do cross module inlinig by default,

Right, it's still experimental and has issues.

>> and LTO only help if your ldc(druntime+phobos) are built with enabled LTO

That's only true if (mostly non-templated) functions in druntime/Phobos are to be cross-module inlined, just like any other library. In that case, you can simply use `-flto=<thin|full> -defaultlib=phobos2-ldc-lto,druntime-ldc-lto` with LDC builds shipping with LTO druntime/Phobos and don't have to recompile druntime/Phobos manually anymore.