[llvm-dev] Please dogfood LLD

[David Blaikie via llvm-dev]

FWIW - selfhosting I did find that GDB wasn't able to find the source code
for some functions when using LLD's gdb_index, so I've switched back to
gold+gdb_index for now (given the performance problems you mentioned,
sounds like I wasn't gaining much/anything in terms of link time by using
lld anyway).

On Thu, Mar 16, 2017 at 11:17 AM Rui Ueyama <ruiu at google.com> wrote:

> I personally haven't tried gdb_index, and I don't know the quality of the
> produced index. Most of the code was written by George.
>
> One thing I noticed about the feature (and filed as
> http://bugs.llvm.org/show_bug.cgi?id=32228) is that our gdb_index feature
> is much slower than the gold. Apparently there's room for improvement.
>
> On Thu, Mar 16, 2017 at 8:35 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
> Any idea of the quality/completeness of the gdb_index support? I've
> started using gdb_index recently (reduces GDB startup time for Clang from
> 50 seconds to 3 seconds - though I haven't measure how much it increases
> link time*) & it's really handy. Would love to have some assurance it's
> expected to work for LLD.
>
> Simple experiments seem to indicate that it's OK/good. Though a quick
> llvm-dwarfdump of gdb_index between the two linkers shows about a 10%
> disparity in size (LLD's is smaller) given the same inputs. (219MB v 196MB
> of text dumped - I didn't compare the actual section sizes)
>
> *though honestly I'd be willing to trade startup time for link time 1:1
> even, because builds/links are already long enough that I go off and do
> something else - whereas getting GDB start down to 3 seconds, I can start
> writing my breakpoint command, etc, in those 3 seconds and be all but
> unaffected by it - at 50 seconds I basically have to go off and do
> something else/context switch/etc.
>
> On Tue, Mar 14, 2017 at 11:40 AM Rui Ueyama via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi all,
>
> LLVM 4.0.0 is out, and I can say that LLD/ELF is now ready for production
> use at least for x86-64 (and probably for AArch64 and MIPS). I believe
> you've heard a few good news about the linker -- it just works
> <http://lld.llvm.org/#features> and is very fast
> <http://lld.llvm.org/#performance>, clean, compact and supported by the
> active community. I don't think I need to reiterate why having a good
> linker is important for us as the LLVM community.
>
> There's one thing you can help us without writing even a line of code.
> Please use it!
>
> Using LLD to link LLVM/clang/etc is easy. You need to check out the LLD
> repository just like you probably already did for clang, build it, and then
> install it. LLD will be installed as ld.lld (and it won't be used by
> default.) After that, re-run cmake with -DLLVM_ENABLE_LLD=On along with
> your usual options so that LLD will be used to build LLVM.
>
> For the details of the build process, please see
> http://lld.llvm.org/#build.
>
> Thanks,
> Rui
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170316/0ceb0d70/attachment.html>