[LLVMdev] Pass Manager Restriction?

[Joseph Blomstedt]

Having a ModulePass that requires a FunctionPass that in turn requires
another ModulePass results in an assertion being fired. Is this
expected behavior (that seems to be undocumented), or a bug?

Specifically, the following code will emit the assertion:
[VMCore/PassManager.cpp:1597: virtual void
llvm::ModulePass::assignPassManager(llvm::PMStack&,
llvm::PassManagerType): Assertion `!PMS.empty() && "Unable to find
appropriate Pass Manager"' failed]

******
struct ModPass1 : public ModulePass {
  static char ID;
  ModPass1() : ModulePass((intptr_t)&ID) {}
  virtual bool runOnModule(Module &M) { return false; }
  virtual void getAnalysisUsage(AnalysisUsage &AU) const {}
};

struct FunPass1 : public FunctionPass {
  static char ID;
  FunPass1() : FunctionPass((intptr_t)&ID) {}
  virtual bool runOnFunction(Function &F) {return false; }
  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
    AU.addRequired<ModPass1>();
  }
};

struct ModPass2 : public ModulePass {
  static char ID;
  ModPass2() : ModulePass((intptr_t)&ID) {}
  virtual bool runOnModule(Module &M) { return false; }
  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
    AU.addRequired<FunPass1>();
  }
};

char ModPass1::ID = 0;
char FunPass1::ID = 0;
char ModPass2::ID = 0;

RegisterPass<ModPass1> A("modpass1", "");
RegisterPass<FunPass1> B("funpass1", "");
RegisterPass<ModPass2> C("modpass2", "");

int main(int argc, char argv) {
  PassManager PM;
  PM.add(new ModPass2);
}
******

Also of note, if the first module requires TargetData, then the code
will fail earlier with the assertion
[include/llvm/Target/TargetData.h:114: llvm::TargetData::TargetData():
Assertion `0 && "ERROR
: Bad TargetData ctor used.  " "Tool did not specify a TargetData to
use?"' failed]. This occurs even when a valid TargetData object is
added to the PassManager. Specifically, if ModPass1 above is
changed to have addRequired<TargetData> then the first of the
following code works, but the second fails with the TargetData
assertion:

******
// Works!
int main(int argc, char argv) {
  PassManager PM;
  Module TestMod = ...;
  PM.add(new TargetData(TestMod));
  PM.add(new FunPass1);
}
******
// Breaks with TargetData assertion rather than PMS.empty assertion
int main(int argc, char argv) {
  PassManager PM;
  Module TestMod = ...;
  PM.add(new TargetData(TestMod));
  PM.add(new ModPass2);
}
******