[llvm-dev] (Thin)LTO llvm build

[Teresa Johnson via llvm-dev]

On Sun, Oct 2, 2016 at 8:45 AM, Xinliang David Li <xinliangli at gmail.com>
wrote:

> bfd linker 2.26 works fine with LLVMgold.so.   As I mentioned in a
> previous email, 2.26 ar and ranlib also works fine as long as LLVMgold.so
> is put in a path binutils know about : $(bindir)/../lib/bfd-plugins/
>

That's interesting. I did not know LLVMgold.so could be used with the bfd
linker. According to http://llvm.org/docs/GoldPlugin.html, LLVM LTO
requires the gold linker. I've never tested with the bfd linker, and will
need to build one and try with it as my system has 2.24.

Teresa


David
>
> On Sun, Oct 2, 2016 at 3:59 AM, Carsten Mattner <carstenmattner at gmail.com>
> wrote:
>
>> On Sun, Oct 2, 2016 at 6:52 AM, Teresa Johnson <tejohnson at google.com>
>> wrote:
>>
>> > But something is odd then - if the builds aren't using gold then I don't
>> > see how ThinLTO could have been kicking in?
>>
>> I'm not an expert on LLVM's build process, but it's important to note
>> that the
>> failure was immediately upon trying to run cmake with the extended
>> LDFLAGS,
>> which now includes the extra flags to enable more pruning.
>>
>> My understaning was that ld.gold is required for the plugin to do ThinLTO,
>> and given my observation before/after enabling llvm-ar/llvm-ranlib to make
>> LTO work, and how long the ld processes took for executables and DSOs,
>> I'm under the impression that ld.gold was actually used.
>>
>
>


-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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