It seems to fix the initial problem, but now I'm getting something else:

PRT: /home/greg/build/llvm/include/llvm/Support/Casting.h:239: typename
cast_retty<X, Y *>::ret_type llvm::cast(Y *) [X = llvm::BranchInst, Y =
llvm::TerminatorInst]: Assertion `isa<X>(Val) && "cast<Ty>() argument of
incompatible type!"' failed.
Stack dump:
0.    Running pass 'Function Pass Manager' on module 'radeon'.
1.    Running pass 'Region Pass Manager' on function '@shadow_ao'
2.    Running pass 'Structurize control flow' on basic block '%if.end100'