[LLVMdev] Remove function from module

[Михаил]

How correctly remove function from module?

For example:

int f1(int x) { 

   ...

   a = f2(smth);

   ...

}

int f2 (int y) {

   ...

   b = f1(smth);

   ...

}

I need delete from module both f1 and f2. They haven't uses in other part of module, but I can't delete them with eraseFromParent, because they are use each other.

Yours sincerely,

Kadysev Mikhail

[Nick Lewycky]

Call X->replaceAllUsesWith(UndefValue::get(X->getType)) before calling
X->eraseFromParent().

Nick
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[Dmitry N. Mikushin]

Hi Михаил,

You can also use GVExtractionPass:

if (!strcmp(argv[1], "pass"))
{
PassManager manager;
manager.add(new TargetData(m.get()));

// Delete functions specified in list of functions.
vector<GlobalValue*> functions;
functions.push_back(m.get()->getFunction("f1"));
functions.push_back(m.get()->getFunction("f2"));
manager.add(createGVExtractionPass(functions, true));

// Delete unreachable globals.
manager.add(createGlobalDCEPass());

// Remove dead debug info.
manager.add(createStripDeadDebugInfoPass());

// Remove dead func decls.
manager.add(createStripDeadPrototypesPass());

manager.run(*m.get());
}

if (!strcmp(argv[1], "manual"))
{
Function* f1 = m.get()->getFunction("f1");
Function* f2 = m.get()->getFunction("f2");

f1->replaceAllUsesWith(UndefValue::get((Type*)f1->getType()));
f2->replaceAllUsesWith(UndefValue::get((Type*)f2->getType()));

f1->eraseFromParent();
f2->eraseFromParent();
}

- D.

2012/4/21 Nick Lewycky <nich...@mxc.ca>:

[Михаил]

Thanks, but I replaceAllUsesWith() - works well, but I still get bug in eraseFromParent():

While deleting: i32 (%class.B*, i32)* %_ZN1B1xEi

An asserting value handle still pointed to this value!

UNREACHABLE executed at /Users/neonomaly/LLVM/LLVM/lib/VMCore/Value.cpp:561!

Yours sincerely,

Kadysev Mikhail

21.04.2012, в 23:45, Nick Lewycky написал(а):

[Dmitry N. Mikushin]

Could you reproduce this assertion with my test program?

22 апреля 2012 г. 0:09 пользователь Михаил <neono...@gmail.com> написал:

[Михаил]

It also occurs on several (different) test cases. I have founded that assershion rises in void ValueHandleBase::ValueIsDeleted(Value *V);

Code from function:

  // All callbacks, weak references, and assertingVHs should be dropped by now.

  if (V->HasValueHandle) {

#ifndef NDEBUG      // Only in +Asserts mode...

    dbgs() << "While deleting: " << *V->getType() << " %" << V->getNameStr()

           << "\n";

    if (pImpl->ValueHandles[V]->getKind() == Assert)

      llvm_unreachable("An asserting value handle still pointed to this

                       " value!");

#endif

    llvm_unreachable("All references to V were not removed?");

  }

Yours sincerely,

Kadysev Mikhail

22.04.2012, в 1:41, Dmitry N. Mikushin написал(а):

Assertion occurs on some different test case? Could you attach its IR-code?

22 апреля 2012 г. 1:38 пользователь Михаил <neono...@gmail.com> написал:

Yes

Yours sincerely,

Kadysev Mikhail

22.04.2012, в 0:30, Dmitry N. Mikushin написал(а):

[Nick Lewycky]

Михаил wrote:
> Thanks, but I replaceAllUsesWith() - works well, but I still get bug in
> eraseFromParent():
>
> While deleting: i32 (%class.B*, i32)* %_ZN1B1xEi
> An asserting value handle still pointed to this value!
> UNREACHABLE executed at /Users/neonomaly/LLVM/LLVM/lib/VMCore/Value.cpp:561!

The replaceAllUsesWith + eraseFromParent pattern remains correct, but
there's more to the story than the parts we've focused on. This error
means that there's some other code that is holding a pointer to the
function you tried to delete, but is using AssertingVH to do so, so as
to catch errors exactly like this producing a dangling pointer.

The error message doesn't tell us who owns the AssertingVH (indeed, the
asserting-vh doesn't know, much like a pointer doesn't know who owns it).

So, under what circumstance are you doing this deletion? Is it inside a
FunctionPass, or another kind of Pass? Are you using AssertingVH's or
calling other code that is? Such as ValueMap's, or some llvm analysis
pass which stores an AssertingVH?

Nick

>
>
> Yours sincerely,
> Kadysev Mikhail
>
> 21.04.2012, в 23:45, Nick Lewycky написал(а):
>
>> Михаил wrote:
>>> How correctly remove function from module?
>>> For example:
>>>
>>> int f1(int x) {
>>> ...
>>> a = f2(smth);
>>> ...
>>> }
>>> int f2 (int y) {
>>> ...
>>> b = f1(smth);
>>> ...
>>> }
>>>
>>> I need delete from module both f1 and f2. They haven't uses in other
>>> part of module, but I can't delete them with eraseFromParent, because
>>> they are use each other.
>>
>> Call X->replaceAllUsesWith(UndefValue::get(X->getType)) before calling
>> X->eraseFromParent().
>>
>> Nick
>
>
>

[Михаил]

It is ModulePass with AnalysisUsage of CallGraph

Yours sincerely,

Kadysev Mikhail

22.04.2012, в 5:20, Nick Lewycky написал(а):

[Nick Lewycky]

Михаил wrote:
> It is ModulePass with AnalysisUsage of CallGraph

Ah, then you'll need to update the CallGraph first. Use
"CG.removeFunctionFromModule(F);" before deleting it.

Nick

>>> LLV...@cs.uiuc.edu <mailto:LLV...@cs.uiuc.edu> http://llvm.cs.uiuc.edu

[Михаил]

Thanks.

I try to delete function like this (rta_IsFunctionVisited.find - set of good functions) :

// delete dead functions

for (Module::iterator Fx = M->begin(), FE = M->end(); Fx!=FE; Fx++) {

if (rta_IsFunctionVisited.find(Fx)==rta_IsFunctionVisited.end()) {

Fx->replaceAllUsesWith(UndefValue::get(Fx->getType()));

}

}

for (CallGraph::iterator CGN = CG.begin(); CGN!=CG.end(); CGN++) {

if (rta_IsFunctionVisited.find(CGN->second->getFunction())==rta_IsFunctionVisited.end()) {

CGN->second->removeAllCalledFunctions();

}

}

for (Module::iterator Fx = M->begin(), FE = M->end(); Fx!=FE;) {

if (rta_IsFunctionVisited.find(Fx)==rta_IsFunctionVisited.end()) {

CallGraphNode *CGN = CG.getOrInsertFunction(Fx);

CG.removeFunctionFromModule(Fx);

wasChanged=true;

Fx=M->begin();

} else Fx++;

}

return true;

But I still have a bug:

opt(63981) malloc: *** error for object 0x7ff1394050a0: pointer being freed was not allocated

*** set a breakpoint in malloc_error_break to debug

0  libLLVM-3.0.dylib 0x00000001082d7605 _ZL15PrintStackTracePv + 53

1  libLLVM-3.0.dylib 0x00000001082d7c6c _ZL13SignalHandleri + 364

2  libsystem_c.dylib 0x00007fff9152dcfa _sigtramp + 26

3  libsystem_c.dylib 0x00007fff66d6a878 _sigtramp + 18446744072996768664

4  libsystem_c.dylib 0x00007fff9152b84c free + 389

5  libLLVM-3.0.dylib 0x00000001083536b0 __gnu_cxx::new_allocator<std::pair<llvm::WeakVH, llvm::CallGraphNode*> >::deallocate(std::pair<llvm::WeakVH, llvm::CallGraphNode*>*, unsigned long) + 32

6  libLLVM-3.0.dylib 0x000000010835360e std::_Vector_base<std::pair<llvm::WeakVH, llvm::CallGraphNode*>, std::allocator<std::pair<llvm::WeakVH, llvm::CallGraphNode*> > >::_M_deallocate(std::pair<llvm::WeakVH, llvm::CallGraphNode*>*, unsigned long) + 62

7  libLLVM-3.0.dylib 0x00000001083535bd std::_Vector_base<std::pair<llvm::WeakVH, llvm::CallGraphNode*>, std::allocator<std::pair<llvm::WeakVH, llvm::CallGraphNode*> > >::~_Vector_base() + 45

8  libLLVM-3.0.dylib 0x0000000108353509 std::vector<std::pair<llvm::WeakVH, llvm::CallGraphNode*>, std::allocator<std::pair<llvm::WeakVH, llvm::CallGraphNode*> > >::~vector() + 105

9  libLLVM-3.0.dylib 0x0000000108353495 std::vector<std::pair<llvm::WeakVH, llvm::CallGraphNode*>, std::allocator<std::pair<llvm::WeakVH, llvm::CallGraphNode*> > >::~vector() + 21

10 libLLVM-3.0.dylib 0x000000010852be3e llvm::CallGraphNode::~CallGraphNode() + 110

11 libLLVM-3.0.dylib 0x0000000108529d55 llvm::CallGraphNode::~CallGraphNode() + 21

12 libLLVM-3.0.dylib 0x0000000108528468 llvm::CallGraph::destroy() + 264

13 libLLVM-3.0.dylib 0x00000001085295f8 (anonymous namespace)::BasicCallGraph::destroy() + 120

14 libLLVM-3.0.dylib 0x0000000108529379 (anonymous namespace)::BasicCallGraph::releaseMemory() + 25

15 libLLVM-3.0.dylib 0x0000000107bf5d93 llvm::PMDataManager::freePass(llvm::Pass*, llvm::StringRef, llvm::PassDebuggingString) + 179

16 libLLVM-3.0.dylib 0x0000000107bf5c89 llvm::PMDataManager::removeDeadPasses(llvm::Pass*, llvm::StringRef, llvm::PassDebuggingString) + 505

17 libLLVM-3.0.dylib 0x0000000107bf8ee8 llvm::MPPassManager::runOnModule(llvm::Module&) + 1016

18 libLLVM-3.0.dylib 0x0000000107bf949c llvm::PassManagerImpl::run(llvm::Module&) + 172

19 libLLVM-3.0.dylib 0x0000000107bf997d llvm::PassManager::run(llvm::Module&) + 29

20 opt               0x000000010717f057 main + 6903

21 opt               0x000000010716d7b4 start + 52

22 opt               0x0000000000000007 start + 18446744069295646855

Yours sincerely,

Kadysev Mikhail

22.04.2012, в 23:30, Nick Lewycky написал(а):