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Michael Muller

2012-Jan-13 17:26 UTC

[LLVMdev] ValueMapper question: no type mapping for GlobalValue?

=?ISO-8859-1?Q?Rafael_=C1vila_de_Esp=EDndola?= wrote:> > I can reproduce this consistently, but only under an extremely large
pile of
> > code :-)  I haven't tried to strip it down to minimal a test case
yet, but I
> > will.  One salient difference with the code you've provided is
that in my
> > code, @a is a struct type.  However, changing the example to use a
minimal
> > structure doesn't trigger the assertion failure.
> 
> Is the example something you can share even in unreduced for?
As it turns out, the root cause was that I had a GlobalVariable that wasn't
being copied to an extern in the new module under some circumstances, but was
being used directly.  I would have expected the verifier pass to catch this,
but it looks like we're probably not using the verifier except when running
non-optimized + debug, which I never tried.

I'll recreate this situation just to verify that the verifier pass
identifies
the problem, if it doesn't I'll proceed from there but I'm currently
assuming
the problem is entirely ours :-)

If you think the behavior of the ValueMapper is incorrect in this situation,
I'd prefer to furnish you with a minimal test case - the unreduced form
involves checking out and building a specific revision of the Crack compiler
and running one of the tests in "native" (AOT compile) mode.

Thank you for looking into this :-)
> 
> > But I'm still curious: why doesn't the value mapper do type
mapping on global
> > variables?
> 
> I am not sure. I would probably have to look at a failing example to
> know what is going on.
> 
> Cheers,
> Rafael
> 

============================================================================michaelMuller
= mmuller at enduden.com | http://www.mindhog.net/~mmuller
-----------------------------------------------------------------------------
We are the music-makers, and we are the dreamers of dreams
 - Arthur O'Shaughnessy
=============================================================================

Michael Muller

2012-Jan-17 13:45 UTC

head link

[LLVMdev] ValueMapper question: no type mapping for GlobalValue?

So it looks like the verifier doesn't catch this condition - I think it
should.  The attached program reproduces the problem - verification succeeds,
but the linker fails with a type assertion.

BTW, if no one has the bandwidth to work on this I'm willing to attempt a
fix,
assuming that you agree that the verifier should discover this condition.

Michael Muller wrote:> 
> =?ISO-8859-1?Q?Rafael_=C1vila_de_Esp=EDndola?= wrote:
> > > I can reproduce this consistently, but only under an extremely
large pile of
> > > code :-)  I haven't tried to strip it down to minimal a test
case yet, but I
> > > will.  One salient difference with the code you've provided
is that in my
> > > code, @a is a struct type.  However, changing the example to use
a minimal
> > > structure doesn't trigger the assertion failure.
> > 
> > Is the example something you can share even in unreduced for?
> 
> As it turns out, the root cause was that I had a GlobalVariable that
wasn't
> being copied to an extern in the new module under some circumstances, but
was
> being used directly.  I would have expected the verifier pass to catch
this,
> but it looks like we're probably not using the verifier except when
running
> non-optimized + debug, which I never tried.
> 
> I'll recreate this situation just to verify that the verifier pass
identifies
> the problem, if it doesn't I'll proceed from there but I'm
currently assuming
> the problem is entirely ours :-)
> 
> If you think the behavior of the ValueMapper is incorrect in this
situation,
> I'd prefer to furnish you with a minimal test case - the unreduced form
> involves checking out and building a specific revision of the Crack
compiler
> and running one of the tests in "native" (AOT compile) mode.
> 
> Thank you for looking into this :-)
> 
> > 
> > > But I'm still curious: why doesn't the value mapper do
type mapping on global
> > > variables?
> > 
> > I am not sure. I would probably have to look at a failing example to
> > know what is going on.
> > 
> > Cheers,
> > Rafael
> > 
> 
> 
>
============================================================================>
michaelMuller = mmuller at enduden.com | http://www.mindhog.net/~mmuller
>
-----------------------------------------------------------------------------
> We are the music-makers, and we are the dreamers of dreams
>  - Arthur O'Shaughnessy
>
============================================================================>
_______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 

============================================================================michaelMuller
= mmuller at enduden.com | http://www.mindhog.net/~mmuller
-----------------------------------------------------------------------------
There is no way to find the best design except to try out as many designs as
possible and discard the failures. - Freeman Dyson
============================================================================--------------
next part --------------
/* build with:
   g++ `llvm-config --cxxflags --cppflags --ldflags`  \
        ReferencingExternalGlobal.cc \
        `llvm-config --libs core jit native instrumentation bitwriter ipo \
         linker` \
        -o ReferencingExternalGlobal
*/

#include <llvm/Module.h>
#include <llvm/Type.h>
#include <llvm/DerivedTypes.h>
#include <llvm/Linker.h>
#include <llvm/LLVMContext.h>
#include <llvm/PassManager.h>
#include <llvm/Analysis/Verifier.h>
#include <llvm/Constants.h>
#include <iostream>

using namespace std;
using namespace llvm;

int main(int argc, const char **argv) {
    LLVMContext &context = getGlobalContext();
    Module *mod1 = new Module("first", context);

    // create my structure type
    vector<Type *> members(1);
    members[0] = Type::getInt32Ty(context);
    StructType *type = StructType::create(context, members, "MyType");

    // create my initializer
    vector<Constant *> memberVals(1);
    memberVals[0] = Constant::getNullValue(Type::getInt32Ty(context));
    Constant *init = ConstantStruct::get(type, memberVals);

    // create a global in the first module
    GlobalVariable *gvar         new GlobalVariable(*mod1, type, false, //
isConstant
                           GlobalValue::ExternalLinkage,
                           init,
                           "my_global_var"
                           );


    Linker *linker = new Linker("linker-name",
"main-module",
                                context, 0);

    string errMsg;
    linker->LinkInModule(mod1, &errMsg);

    Module *mod2 = new Module("second", context);
    GlobalVariable *refGVar         new GlobalVariable(*mod2,
type->getPointerTo(), false,
                           GlobalValue::ExternalLinkage,
                           gvar,
                           "referencing_variable"
                           );

    // do the verifier pass (completes successfully)
    PassManager pm;
    pm.add(createVerifierPass());
    pm.run(*mod2);

    // link mod2 (causes assertion failure)
    linker->LinkInModule(mod2, &errMsg);
}

Duncan Sands

2012-Nov-15 10:34 UTC

head link

[LLVMdev] ValueMapper question: no type mapping for GlobalValue?

Hi Michael, did anything ever happen with this?

Ciao, Duncan.

On 17/01/12 14:45, Michael Muller wrote:>
> So it looks like the verifier doesn't catch this condition - I think it
> should.  The attached program reproduces the problem - verification
succeeds,
> but the linker fails with a type assertion.
>
> BTW, if no one has the bandwidth to work on this I'm willing to attempt
a fix,
> assuming that you agree that the verifier should discover this condition.
>
> Michael Muller wrote:
>>
>> =?ISO-8859-1?Q?Rafael_=C1vila_de_Esp=EDndola?= wrote:
>>>> I can reproduce this consistently, but only under an extremely
large pile of
>>>> code :-)  I haven't tried to strip it down to minimal a
test case yet, but I
>>>> will.  One salient difference with the code you've provided
is that in my
>>>> code, @a is a struct type.  However, changing the example to
use a minimal
>>>> structure doesn't trigger the assertion failure.
>>>
>>> Is the example something you can share even in unreduced for?
>>
>> As it turns out, the root cause was that I had a GlobalVariable that
wasn't
>> being copied to an extern in the new module under some circumstances,
but was
>> being used directly.  I would have expected the verifier pass to catch
this,
>> but it looks like we're probably not using the verifier except when
running
>> non-optimized + debug, which I never tried.
>>
>> I'll recreate this situation just to verify that the verifier pass
identifies
>> the problem, if it doesn't I'll proceed from there but I'm
currently assuming
>> the problem is entirely ours :-)
>>
>> If you think the behavior of the ValueMapper is incorrect in this
situation,
>> I'd prefer to furnish you with a minimal test case - the unreduced
form
>> involves checking out and building a specific revision of the Crack
compiler
>> and running one of the tests in "native" (AOT compile) mode.
>>
>> Thank you for looking into this :-)
>>
>>>
>>>> But I'm still curious: why doesn't the value mapper do
type mapping on global
>>>> variables?
>>>
>>> I am not sure. I would probably have to look at a failing example
to
>>> know what is going on.
>>>
>>> Cheers,
>>> Rafael
>>>
>>
>>
>>
============================================================================>>
michaelMuller = mmuller at enduden.com | http://www.mindhog.net/~mmuller
>>
-----------------------------------------------------------------------------
>> We are the music-makers, and we are the dreamers of dreams
>>   - Arthur O'Shaughnessy
>>
============================================================================>>
_______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
>
>
============================================================================>
michaelMuller = mmuller at enduden.com | http://www.mindhog.net/~mmuller
>
-----------------------------------------------------------------------------
> There is no way to find the best design except to try out as many designs
as
> possible and discard the failures. - Freeman Dyson
>
============================================================================>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>

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