[llvm-dev] How to split module into several ones

[Teresa Johnson via llvm-dev]

On Thu, Nov 17, 2016 at 1:37 AM, Aliaksei Zasenka via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi John,
> Thanks for your answer.
>
> The CallGraph pass did the work for me. But since I actually have several
> modules and my toolchain looked like
>
> llvm-link
> <CallGraph extraction pass>
> opt
> llc
>
>  I've found that llvm-lto is great for doing all the work: greedy linkage,
> optimization and further MC generation.
> Here the command line I'm using for that:
> llvm-lto -exported-symbol=main -save-merged-module -filetype=asm <or obj>
> -o %t2 %t1
> (I've attached corresponding llvm-lit test.)
>
> Now I'm wondering if there is any possibility to use LTO within the linker
> like ld (mingw) to build a dynamic library from my IR code?
>

What is your ld version? The Gold ld can invoke LLVM's gold-plugin when
given bitcode input files, which will perform LTO. However, while the GNU
ld recently gained the ability to invoke LLVM's gold-plugin to do this for
bitcode, it is not a configuration we test, so I'd recommend Gold ld. Also,
LLVM's lld has support for bitcode inputs and will also invoke LTO. For the
gold plugin, see http://llvm.org/docs/GoldPlugin.html for ensuring it is
configured properly.

Teresa


> Best regards,
> Alexey Zasenko
>
>
> 2016-10-28 16:33 GMT+03:00 John Criswell <jtcriswel at gmail.com>:
>
>> On 10/27/16 11:18 AM, Aliaksei Zasenka via llvm-dev wrote:
>>
>> Hi all,
>> Can anyone give me advice about an appropriate way for extracting number
>> of functions from module recursively (starting from entry point). Actually
>> it may be more than one entry point so all dependent functions and global
>> values must be extracted.
>>
>> I've tried llvm-extract tool but it can't do work recursively. Maybe it
>> would be good to write some Call Graph pass or something. Any thoughts?
>>
>>
>> I thought llvm-extract conservatively extracted anything that was
>> relevant to what it was asked to extract.
>>
>> In any event, if you need a call graph analysis, there are two call graph
>> passes available for LLVM.
>>
>> The first is the CallGraph pass that comes in the LLVM source tree.  It
>> is very conservative with function pointers, but its results are
>> conservatively correct.
>>
>> The second is the CallGraph analysis within DSA.  You should be able to
>> find a copy for LLVM 3.7 or LLVM 3.8 here (https://github.com/jtcriswell
>> /safecode-llvm37) and here (https://github.com/jtcriswell/llvm-dsa).
>>
>> Regards,
>>
>> John Criswell
>>
>>
>>
>> Thanks in advance,
>> Alexey Zasenko
>>
>>
>> _______________________________________________
>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>>
>> --
>> John Criswell
>> Assistant Professor
>> Department of Computer Science, University of Rochesterhttp://www.cs.rochester.edu/u/criswell
>>
>>
>
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>


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