[LLVMdev] Patch: PassManager should call add() instead of addLowerLevelRequiredPass()

[Kevin Fan]

Hello,

LLVM asserts in the following scenario.  Say there are three passes:
A, B, C.  C requires A and B; B requires A; and B does not preserve A.
 A valid pass ordering would be A B A C.  However, opt gives the
following assertion:

$ opt -load libPassTest.so foo.bc -f -o /dev/null -c -debug-pass=Structure
opt: /u/loc/kevin/llvm/llvm/lib/VMCore/PassManager.cpp:1424: virtual
void llvm::MPPassManager::addLowerLevelRequiredPass(llvm::Pass*,
llvm::Pass*): Assertion `(P->getPotentialPassManagerType() <
RequiredPass->getPotentialPassManagerType()) && "Unable to handle Pass
that requires lower level Analysis pass"' failed.

even though all passes are ModulePasses and do not require lower level passes.

The attached patch modifies PMDataManager::add() to check if the
required pass is actually a lower level pass before calling
addLowerLevelRequiredPass(); if not, it calls add() instead.  Not sure
if this is the best fix, but it works for me.

I also attached a test case with the three passes A, B, C described above.

Kevin
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