[LLVMdev] Cannot use function pass in a module pass

[John Criswell]

On 6/16/11 12:22 PM, Alexey Bakhirkin wrote:
> Thanks, John.
> There were a couple of function declarations in the module, and
> 'getAnalysis' failed for those.
>
> By the way, what do you mean by "in older versions of LLVM"? I'm quite
> sure I was using the latest llvm trunk.

What I meant was that I am using an older version of LLVM; in that older 
version (LLVM 2.7), trying to run a FunctionPass on a function without a 
body triggers an assertion.  It is possible that newer versions of LLVM 
don't trigger the assertion, but I tend to suspect that the behavior has 
remained unchanged.

-- John T.

> 2011/6/16 John Criswell<criswell at cs.uiuc.edu>:
>> On 6/15/11 6:46 PM, Alexey Bakhirkin wrote:
>>> Hi. I'm trying to implement a module pass which can be dynamically
>>> loaded by `opt` (against up-to-date llvm from svn).
>>> Despite what the tutorial
>>> (http://llvm.org/docs/WritingAnLLVMPass.html) states in my module pass
>>> I cannot perform getAnalysis and fetch the function pass result.
>>> When trying to do so `opt` fails with the following mesage:
>> This may not be your problem, but in older versions of LLVM, you cannot
>> call getAnalysis<FunctionPassName>(F) if F is a function with no body.
>> You need to do something like:
>>
>> if (!(F->isDeclaration())) {
>>      getAnalysis<FunctionPassName>(F);
>>      ...
>> }
>>
>> -- John T.
>>
>>> [***@*** ***]$ opt -load ~/llvm/Debug+Asserts/lib/MyPassLibrary.so
>>> -mymodulepass<    input.bc>/dev/null
>>> MyModulePass::runOnModule
>>> MyFunctionPass::runOnFunction(process)
>>> opt: /***/llvm/include/llvm/MyFunctionPass.h:241: AnalysisType&
>>> llvm::Pass::getAnalysisID(llvm::AnalysisID, llvm::Function&) [with
>>> AnalysisType = {anonymous}::MyFunctionPass, llvm::AnalysisID = const
>>> void*]: Assertion `ResultPass&&    "Unable to find requested analysis
>>> info"' failed.
>>> 0  opt             0x0000000000dbcd86
>>> 1  opt             0x0000000000dbcb82
>>> 2  libpthread.so.0 0x0000003b8f00eeb0
>>> 3  libc.so.6       0x0000003b8e835285 gsignal + 53
>>> 4  libc.so.6       0x0000003b8e836b9b abort + 379
>>> 5  libc.so.6       0x0000003b8e82dc0e
>>> 6  libc.so.6       0x0000003b8e82dcb2
>>> 7  MyPassLibrary.so 0x00007fb2989ce7e8
>>> 8  MyPassLibrary.so 0x00007fb2989ce59f
>>> 9  MyPassLibrary.so 0x00007fb2989ce401
>>> 10 opt             0x0000000000d39af7
>>> llvm::MPPassManager::runOnModule(llvm::Module&) + 453
>>> 11 opt             0x0000000000d39ff8
>>> llvm::PassManagerImpl::run(llvm::Module&) + 130
>>> 12 opt             0x0000000000d3a3ff llvm::PassManager::run(llvm::Module&) + 39
>>> 13 opt             0x00000000008c6803 main + 4561
>>> 14 libc.so.6       0x0000003b8e82139d __libc_start_main + 237
>>> 15 opt             0x00000000008b7b69
>>> Stack dump:
>>> 0.    Program arguments: opt -load
>>> /***/llvm/Debug+Asserts/lib/MyPassLibrary.so -mymodulepass
>>> 1.    Running pass 'My module pass' on module '<stdin>'.
>>> Aborted
>>>
>>> --------
>>>
>>> My code is similar to the following:
>>>
>>> #include "llvm/Pass.h"
>>> #include "llvm/Function.h"
>>> #include "llvm/Module.h"
>>> #include "llvm/Support/raw_ostream.h"
>>>
>>> using namespace llvm;
>>>
>>> namespace {
>>>     struct MyFunctionPass : public FunctionPass {
>>>       static char ID;
>>>       MyFunctionPass() : FunctionPass(ID) {};
>>>
>>>       virtual bool runOnFunction(Function&F) {
>>>         errs()<<    "MyFunctionPass::runOnFunction("<<    F.getName()<<    ")"<<    '\n';
>>>         return false;
>>>       }
>>>     };
>>> }
>>>
>>> char MyFunctionPass::ID = 0;
>>> static RegisterPass<MyFunctionPass>    MyFunctionPassPass("myfunctionpass",
>>>     "My function pass");
>>>
>>> namespace {
>>>     struct MyModulePass : public ModulePass {
>>>       static char ID;
>>>       MyModulePass() : ModulePass(ID) {};
>>>
>>>       virtual bool runOnModule(Module&M) {
>>>         errs()<<    "MyModulePass::runOnModule"<<    '\n';
>>>
>>>         for(Module::iterator FI=M.begin(), E=M.end(); FI!=E; ++FI) {
>>>           getAnalysis<MyFunctionPass>(*FI);
>>>         }
>>>
>>>         return false;
>>>       }
>>>
>>>       virtual void getAnalysisUsage(AnalysisUsage&AU) const {
>>>         AU.addRequired<MyFunctionPass>();
>>>       }
>>>     };
>>> }
>>>
>>> char MyModulePass::ID = 0;
>>> static RegisterPass<MyModulePass>    MyModulePassPass("mymodulepass",
>>>     "My module pass");
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