[llvm-dev] saving and restoring multiple modules for Orc JIT

[Lang Hames via llvm-dev]

Hi Geoff,

If I save each module to its own file, I have no problem. But I would like
> to save them to a single file. When I do that, I sometimes get duplicate
> symbol definitions when I reload the modules:
>     Duplicate definition of symbol '$./path/to/my/file.bc.__inits.0'


That's a pseudo-symbol representing the static initializers. Orc
auto-generates it based on the module identifier, and the module identifier
defaults to the path-name of the module file (I don't recall whether this
happens when the module is stored or loaded). I think you could fix this by
setting the module identifier for each module to a unique string (via
Module::setModuleIdentifier) before adding it to the JIT.

I'll see if I can add de-duping logic to the JIT API side too.

-- Lang.

On Sat, Feb 6, 2021 at 12:32 AM Geoff Levner <glevner at gmail.com> wrote:

> Well, I have worked around this problem by implementing my own little file
> format to hold the simple concatenation of any number of bitcode files. It
> does not seem like this should be necessary, though. If anyone comes up
> with a better solution in the future, I am interested...
>
> Geoff
>
> On Tue, Feb 2, 2021 at 12:26 PM Geoff Levner <glevner at gmail.com> wrote:
>
>> Greetings, LLVM developers.
>>
>> I am trying to save the bitcode for multiple modules so that I can reload
>> them later and add them to my Orc-based JIT.
>>
>> If I save each module to its own file, I have no problem. But I would
>> like to save them to a single file. When I do that, I sometimes get
>> duplicate symbol definitions when I reload the modules:
>>
>>     Duplicate definition of symbol '$./path/to/my/file.bc.__inits.0'
>>
>> It looks to me as though this is a problem with static constructors in
>> the modules, as though each module puts its constructors in a symbol with
>> the same name...?
>>
>> Does anybody have a better idea than I am of what is going on, or how to
>> solve this?
>>
>> I am using the 11.x release branch on Linux, FWIW. To reload the modules,
>> I use a call to getBitcodeModuleList(), followed by calls to
>> BitcodeModule::parseModule(), and finally calls to
>> orc::LLJIT::addIRModule().
>>
>> Geoff
>>
>
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