llvm dev - Oct 2016 - [help] How to speed up compilation?

On 18 October 2016 at 07:51, Renato Golin via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> A few hints:
Another one for debug builds on Linux is using split debug info:
-DLLVM_USE_SPLIT_DWARF=ON. This speeds up links dramatically (and
reduces memory consumption) as long as you've got a new enough gdb (I
think lldb is still not quite up to it). It has no effect on macOS
though, because a similar configuration is just how things work there.

Tim.

These are two comprehensive blog posts about how to compile llvm/clang faster:

https://blogs.s-osg.org/an-introduction-to-accelerating-your-build-with-clang/
<https://blogs.s-osg.org/an-introduction-to-accelerating-your-build-with-clang/>
https://blogs.s-osg.org/a-conclusion-to-accelerating-your-build-with-clang/
<https://blogs.s-osg.org/a-conclusion-to-accelerating-your-build-with-clang/>

- Matthias
> On Oct 18, 2016, at 7:56 AM, Tim Northover via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> On 18 October 2016 at 07:51, Renato Golin via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> A few hints:
> 
> Another one for debug builds on Linux is using split debug info:
> -DLLVM_USE_SPLIT_DWARF=ON. This speeds up links dramatically (and
> reduces memory consumption) as long as you've got a new enough gdb (I
> think lldb is still not quite up to it). It has no effect on macOS
> though, because a similar configuration is just how things work there.
> 
> Tim.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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I'll try those guys! Thanks for advices, all!

Btw, I have a question.
Personally, it feels like compilation become much slower than previous
versions after adopting 'cmake'.
Is this natural when we adopt cmake or are there other big changes on build
structure?
I'm not that familiar with huge system like llvm yet, so I want to catch up
how professionals design their system.



On Tue, Oct 18, 2016 at 12:22 PM, Matthias Braun <mbraun at apple.com>
wrote:
> These are two comprehensive blog posts about how to compile llvm/clang
> faster:
>
> https://blogs.s-osg.org/an-introduction-to-accelerating-
> your-build-with-clang/
> https://blogs.s-osg.org/a-conclusion-to-accelerating-
> your-build-with-clang/
>
> - Matthias
>
> On Oct 18, 2016, at 7:56 AM, Tim Northover via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> On 18 October 2016 at 07:51, Renato Golin via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>
> A few hints:
>
>
> Another one for debug builds on Linux is using split debug info:
> -DLLVM_USE_SPLIT_DWARF=ON. This speeds up links dramatically (and
> reduces memory consumption) as long as you've got a new enough gdb (I
> think lldb is still not quite up to it). It has no effect on macOS
> though, because a similar configuration is just how things work there.
>
> Tim.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>

-- 
Best, Sung
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> On 18 Oct 2016, at 15:56, Tim Northover via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> On 18 October 2016 at 07:51, Renato Golin via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> A few hints:
> 
> Another one for debug builds on Linux is using split debug info:
> -DLLVM_USE_SPLIT_DWARF=ON. This speeds up links dramatically (and
> reduces memory consumption) as long as you've got a new enough gdb (I
> think lldb is still not quite up to it). It has no effect on macOS
> though, because a similar configuration is just how things work there.
> 
> Tim.
IIRC, ccache only learned about split dwarf fairly recently and the version on
Debian stable didn't know about it. I think that the result was that ccache
always gave up and called the real compiler. I remember split dwarf being the
bigger win of the two but I haven't kept any numbers on it.