llvm dev - Apr 2020 - LLVM 10 ORC2 issue with symbol resolution

Hi,

I updated my project to LLVM 10.0 today and I am getting JIT symbol
resolution errors.
I could not find any example or updated tutorial or documentation that
describes the new api - as all documentation seems out of date.

I paste below some code snippets that show what I am doing:

/* global syms is a array mapping names to function addresses */

ES->createJITDylib("<main>");
MainJD = ES->getJITDylibByName("<main>");
MainJD->addGenerator(
    cantFail(llvm::orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(
        DL->getGlobalPrefix())));
auto &JD = *MainJD;
llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
llvm::orc::SymbolMap Symbols;
for (int i = 0; global_syms[i].name != nullptr; i++) {
  Symbols.insert({mangle(global_syms[i].name),

llvm::JITEvaluatedSymbol(llvm::pointerToJITTargetAddress(global_syms[i].address),

llvm::JITSymbolFlags(llvm::JITSymbolFlags::FlagNames::Absolute))});
}
llvm::cantFail(JD.define(llvm::orc::absoluteSymbols(Symbols)), "Failed
to install extern symbols");

FYI - my previous post on similar issue.
Basically I haven't been able to get ORC v2 working - tried in 8, 9 and now
10.

http://llvm.1065342.n5.nabble.com/llvm-dev-ORC-v2-question-tp130489p130601.html

Thanks and Regards
Dibyendu

Hi Dibyendu,

I updated my project to LLVM 10.0 today and I am getting
JIT
> symbol resolution errors.
> I could not find any example or updated tutorial or documentation
> that describes the new api - as all documentation seems out of date.

The doxygen comments should be up-to-date, as should
http://llvm.org/docs/ORCv2.html. You can find up-to-date example code for
LLJIT in llvm/examples/LLJITExamples (LLVM 10) or
llvm/examples/OrcV2Examples (master). If you come across any documentation
in master that appears to be out of date please let me know and I will fix
it.

The BuildingAJIT tutorial series is known to be out of date. I'm hoping to
have that fixed by LLVM 11 but there is some feature work that I need to
complete first.

Can you share the specific errors that you're getting back? I would
recommend replacing

cantFail(callToFailingFunc(...));

with

logAllUnhandledErrors(callToFailingFunc(...), errs(),
"callToFailingFunc(...) failed:");

Regards,
Lang.

On Mon, Apr 13, 2020 at 10:06 AM Dibyendu Majumdar <mobile at
majumdar.org.uk>
wrote:
> Hi,
>
> I updated my project to LLVM 10.0 today and I am getting JIT symbol
> resolution errors.
> I could not find any example or updated tutorial or documentation that
> describes the new api - as all documentation seems out of date.
>
> I paste below some code snippets that show what I am doing:
>
> /* global syms is a array mapping names to function addresses */
>
> ES->createJITDylib("<main>");
> MainJD = ES->getJITDylibByName("<main>");
> MainJD->addGenerator(
>
> cantFail(llvm::orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(
>         DL->getGlobalPrefix())));
> auto &JD = *MainJD;
> llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
> llvm::orc::SymbolMap Symbols;
> for (int i = 0; global_syms[i].name != nullptr; i++) {
>   Symbols.insert({mangle(global_syms[i].name),
>
>
>
llvm::JITEvaluatedSymbol(llvm::pointerToJITTargetAddress(global_syms[i].address),
>
> llvm::JITSymbolFlags(llvm::JITSymbolFlags::FlagNames::Absolute))});
> }
> llvm::cantFail(JD.define(llvm::orc::absoluteSymbols(Symbols)), "Failed
> to install extern symbols");
>
> FYI - my previous post on similar issue.
> Basically I haven't been able to get ORC v2 working - tried in 8, 9 and
> now 10.
>
>
>
http://llvm.1065342.n5.nabble.com/llvm-dev-ORC-v2-question-tp130489p130601.html
>
> Thanks and Regards
> Dibyendu
>
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Hi Lang,

On Mon, 13 Apr 2020 at 19:12, Lang Hames <lhames at gmail.com>
wrote:
>
>> I updated my project to LLVM 10.0 today and I am getting JIT symbol
resolution errors.
>> I could not find any example or updated tutorial or documentation that
describes the new api - as all documentation seems out of date.
>
>
> The doxygen comments should be up-to-date, as should
http://llvm.org/docs/ORCv2.html. You can find up-to-date example code for LLJIT
in llvm/examples/LLJITExamples (LLVM 10) or llvm/examples/OrcV2Examples
(master). If you come across any documentation in master that appears to be out
of date please let me know and I will fix it.
>
Sadly http://llvm.org/docs/ORCv2.html is out of date. For example:

auto &JD = ES.getMainJITDylib();

This api no longer exists.

I did look at OrcV2Examples but did not see any that were trying to
set up external symbols. Did I miss something?
> The BuildingAJIT tutorial series is known to be out of date. I'm hoping
to have that fixed by LLVM 11 but there is some feature work that I need to
complete first.
>
> Can you share the specific errors that you're getting back? I would
recommend replacing
>
> cantFail(callToFailingFunc(...));
>
> with
>
> logAllUnhandledErrors(callToFailingFunc(...), errs(),
"callToFailingFunc(...) failed:");
>
Okay thank you - I will do that and report back.
> On Mon, Apr 13, 2020 at 10:06 AM Dibyendu Majumdar <mobile at
majumdar.org.uk> wrote:
>>
>> Hi,
>>
>> I updated my project to LLVM 10.0 today and I am getting JIT symbol
>> resolution errors.
>> I could not find any example or updated tutorial or documentation that
>> describes the new api - as all documentation seems out of date.
>>
>> I paste below some code snippets that show what I am doing:
>>
>> /* global syms is a array mapping names to function addresses */
>>
>> ES->createJITDylib("<main>");
>> MainJD = ES->getJITDylibByName("<main>");
>> MainJD->addGenerator(
>>    
cantFail(llvm::orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(
>>         DL->getGlobalPrefix())));
>> auto &JD = *MainJD;
>> llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
>> llvm::orc::SymbolMap Symbols;
>> for (int i = 0; global_syms[i].name != nullptr; i++) {
>>   Symbols.insert({mangle(global_syms[i].name),
>>
>>
llvm::JITEvaluatedSymbol(llvm::pointerToJITTargetAddress(global_syms[i].address),
>>
>> llvm::JITSymbolFlags(llvm::JITSymbolFlags::FlagNames::Absolute))});
>> }
>> llvm::cantFail(JD.define(llvm::orc::absoluteSymbols(Symbols)),
"Failed
>> to install extern symbols");
>>
>> FYI - my previous post on similar issue.
>> Basically I haven't been able to get ORC v2 working - tried in 8, 9
and now 10.
>>
>>
http://llvm.1065342.n5.nabble.com/llvm-dev-ORC-v2-question-tp130489p130601.html
>>
>> Thanks and Regards
>> Dibyendu

Hi Dibyendu,

I am not sure the --export-dynamic applies as I am
explicitly
> registering my symbols.
> llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
> llvm::orc::SymbolMap Symbols;
> for (int i = 0; global_syms[i].name != nullptr; i++) {
>   Symbols.insert({mangle(global_syms[i].name),

Ahh. You're right: If you are managing registration yourself then process
symbol visibility should not be an issue.

In this case the first thing that I would do to diagnose the problem is
dump the content of your Symbols map and ensure that there really is an
entry in there for the symbols that generated the missing-symbols error
(luaV_tointeger_ and luaG_runerror).

llvm::JITSymbolFlags::FlagNames::Absolute


This can just be written as llvm::JITSymbolFlags::Absolute. If the JITDylib
you are putting this in is different from the one that you're adding
JIT'd
code to you will also need to make sure that the symbol is exported:

llvm::JITSymbolFlags Flags;
Flags |= llvm::JITSymbolFlags::Absolute;
Flags |= llvm::JITSymbolFlags::Exported;

Symbols that are not marked exported are hidden and not visible by default
to code in other JITDylibs.

Regards,
Lang.

On Mon, Apr 13, 2020 at 1:43 PM Dibyendu Majumdar <mobile at
majumdar.org.uk>
wrote:
> Hi Lang,
>
> On Mon, 13 Apr 2020 at 21:22, Lang Hames <lhames at gmail.com> wrote:
>
> >> Sadly http://llvm.org/docs/ORCv2.html is out of date. For example:
> >> auto &JD = ES.getMainJITDylib();
> >> This api no longer exists.
> >
> >
> > Thanks for spotting that. I have fixed it in 840a23b0b5c. If you see
any
> other issues with the documentation please let me know, or file a bug at
> bugs.llvm.org.
> >
> >> I did look at OrcV2Examples but did not see any that were trying
to set
> up external symbols. Did I miss something?
> >
> >
> > No. I usually point people to lli.cpp for that example:
>
https://github.com/llvm/llvm-project/blob/68cd4f72beae67a9bdbc11c85fd745dec8fc0999/llvm/tools/lli/lli.cpp#L805
> :
> >
> >     J->getMainJITDylib().addGenerator(
> >
>  ExitOnErr(orc::DynamicLibrarySearchGenerator::GetForCurrentProcess(
> >             J->getDataLayout().getGlobalPrefix(),
> >             [MainName = Mangle("main")](const
orc::SymbolStringPtr
> &Name) {
> >               return Name != MainName;
> >             })));
> >
> > The second argument (the lambda) is an optional predicate to filter
out
> some process symbols. Here it is filtering lookups for main to ensure that
> we don't call the process main and overflow the stack when JIT'd
code
> doesn't define a main function.
> >
> > To ensure this works you must (1) use the correct global prefix for
your
> target for both the generator and for any modules that you add to the JIT,
> and (2) ensure that process symbols have to be exported. On Darwin this
> happens by default. On Linux you need to add --export-dynamic to your
> linker line. I assume there is a similar option on Windows but I am not
> familiar with it.
> >
>
> I am not sure the --export-dynamic applies as I am explicitly
> registering my symbols.
>
> llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
> llvm::orc::SymbolMap Symbols;
> for (int i = 0; global_syms[i].name != nullptr; i++) {
>   Symbols.insert({mangle(global_syms[i].name),
>
>
>
llvm::JITEvaluatedSymbol(llvm::pointerToJITTargetAddress(global_syms[i].address),
>
> llvm::JITSymbolFlags(llvm::JITSymbolFlags::FlagNames::Absolute))});
> }
> llvm::cantFail(JD.define(llvm::orc::absoluteSymbols(Symbols)), "Failed
> to install extern symbols");
>
> So the JITDylib should know about the symbols, right?
>
> BTW ORC v1 works fine in LLVM 10, 9 and 8.
>
> Thanks and Regards
>
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Hi Lang,

On Mon, 13 Apr 2020 at 22:00, Lang Hames <lhames at gmail.com>
wrote:
>> I am not sure the --export-dynamic applies as I am explicitly
>> registering my symbols.
>> llvm::orc::MangleAndInterner mangle(*ES, *this->DL);
>> llvm::orc::SymbolMap Symbols;
>> for (int i = 0; global_syms[i].name != nullptr; i++) {
>>   Symbols.insert({mangle(global_syms[i].name),
>
>
> Ahh. You're right: If you are managing registration yourself then
process symbol visibility should not be an issue.
>
> In this case the first thing that I would do to diagnose the problem is
dump the content of your Symbols map and ensure that there really is an entry in
there for the symbols that generated the missing-symbols error (luaV_tointeger_
and luaG_runerror).
>
>> llvm::JITSymbolFlags::FlagNames::Absolute
>
Looks like you are right - I wasn't registering all the functions I
thought I was. So it is a user error.

Thanks for the help.

Regards
Dibyendu