llvm irbuilder call instruction throwing exception on function inlining pass

Question

I'm new to LLVM. I am using the clang c++ API to compile multiple stub files (in c) to IR, and then stick them together using IR builder (after linking them) to eventually run via JIT.

All this works great, unless I add a functionInlining pass to my optimizations, at which point one of these function calls made in IR builder will trigger the following exception when the pass manager is run:

Assertion failed: (New->getType() == getType() && "replaceAllUses of value with new value of different type!"), function replaceAllUsesWith, file /Users/mike/Development/llvm/llvm/lib/IR/Value.cpp, line 356.

This is how I make the call instruction (pretty straight forward):

Function *kernelFunc = mModule->getFunction( (kernel->Name() + StringRef("_") + StringRef(funcName)).str());
if (kernelFunc){
    CallInst* newInst = builder.CreateCall(kernelFunc, args);
}

Later the module is optimized:

legacy::PassManager passMan;
PassManagerBuilder Builder;
Builder.OptLevel = 3;
//Builder.Inliner = llvm::createFunctionInliningPass(); //commenting this back in trigger the exception
Builder.populateModulePassManager(passMan);

passMan.run( *mModule ); //exception occurs before this call returns

Any ideas what to look for?

Colin LeMahieu Colin LeMahieu · Accepted Answer · 2015-12-19T06:58:03

Try running llvm::verifyModule on your module to see if it's correct. You might have an error and have been getting lucky beforehand but it tripped something up in the inliner.

In general assertions check a subset of things that can be wrong with your module but verify checks a lot more.

It could be a bug in LLVM but more than likely it's a bad module, it's easy to happen.

llvm irbuilder call instruction throwing exception on function inlining pass

2 Answers