[llvm-dev] GlobalVariable I inserted gets removed by LTO

[Gleb Popov via llvm-dev]

On Mon, Jul 22, 2019 at 6:39 PM Teresa Johnson <tejohnson at google.com> wrote:

> You should add your GVs to the llvm.used variable or the
> llvm.compiler.used variable (see
> https://llvm.org/docs/LangRef.html#the-llvm-used-global-variable).
> Otherwise it looks globally dead to the linker and LTO. Look at
> existingcalls to llvm::appendToUsed for examples.
>
> Teresa
>

Thank you, that worked!


> On Mon, Jul 22, 2019 at 7:34 AM Gleb Popov via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hello llvm-dev@
>>
>> I have a pass that puts a global constant data array into the module. And
>> another pass that gets runned by lld during LTO stage.
>>
>> When I look at bytecode files corresponding to source TUs produced by
>> `clang -flto`, I can see GVs inserted by my pass #1. However, when pass #2
>> gets to run, these GV's are gone.
>>
>> I figured out that passing -mllvm -compute-dead=0 to the linker fixes the
>> problem, but I'm not sure if it is right thing to do. Ideally, I'd like to
>> trick LTO to ignore only mine GVs during compute-dead analysis.
>>
>> I even tried creating another function that "uses" created GV, but it
>> also got deleted.
>>
>> Any hints?
>>
>> Thanks in advance.
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
>
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