[LLVMdev] Lifetime analysis of variables within a module

Antonio Martínez Álvarez amartinez76 at gmail.com
Wed Oct 31 08:49:15 PDT 2012

Hi all,

I'm looking for a LLVM method/class/strategy to know the lifetime of 
every variable/value used in a given Module.
I want to know the variables that must be alive at the input and at the 
end of every function call (and every BasicBlock).

By creating a pass inheriting from  ModulePass I can reach up to here:

virtual bool runOnFunction(Function &F) {
   for (Function::iterator bbi = F.begin(), bbf = F.end(); bbi != bbf; 
     for (BasicBlock::iterator insi = bbi->begin(), insf = bbi->end(); 
insi != insf; insi++)
         for (User::op_iterator opi = insi->op_begin(), opf = 
insi->op_end(); opi != opf; opi++)

                 if(isa<Instruction>(opi) || isa<Argument>(opi))

                 // Here I am <===============


How can I use LiveIntervals/LiveVariables/LiveRange to obtain the live 
range for a given variable of interest?

BTW, do you know any working example of using MachineFunctionPass or 
LiveIntervals LLVM passes? Every time I use it, opt generates output 
such as:

opt: PassManager.cpp:597: void 
llvm::PMTopLevelManager::schedulePass(llvm::Pass*): Assertion `PI && 
"Expected required passes to be initialized"' failed.
0  libLLVM-3.1.so  0x00007f42eb6469ef
7  libLLVM-3.1.so  0x00007f42eb1ccafa 
llvm::PMTopLevelManager::schedulePass(llvm::Pass*) + 1226

Thank you in advance !!!!

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