diff options
| -rw-r--r-- | lib/Transforms/Scalar/SimplifyCFG.cpp | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/SimplifyCFG.cpp b/lib/Transforms/Scalar/SimplifyCFG.cpp index 0f9946e6ee..af1663c8db 100644 --- a/lib/Transforms/Scalar/SimplifyCFG.cpp +++ b/lib/Transforms/Scalar/SimplifyCFG.cpp @@ -20,6 +20,8 @@ #include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Utils/Local.h" +#include "llvm/Constants.h" +#include "llvm/Instructions.h" #include "llvm/Module.h" #include "llvm/Support/CFG.h" #include "llvm/Pass.h" @@ -45,6 +47,31 @@ static bool MarkAliveBlocks(BasicBlock *BB, std::set<BasicBlock*> &Reachable) { if (Reachable.count(BB)) return false; Reachable.insert(BB); + // Do a quick scan of the basic block, turning any obviously unreachable + // instructions into LLVM unreachable insts. The instruction combining pass + // canonnicalizes unreachable insts into stores to null or undef. + for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ++BBI) + if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) + if (isa<ConstantPointerNull>(SI->getOperand(1)) || + isa<UndefValue>(SI->getOperand(1))) { + // Loop over all of the successors, removing BB's entry from any PHI + // nodes. + for (succ_iterator I = succ_begin(BB), SE = succ_end(BB); I != SE; ++I) + (*I)->removePredecessor(BB); + + new UnreachableInst(SI); + std::cerr << "Inserted UNREACHABLE instruction!\n"; + + // All instructions after this are dead. + for (; BBI != E; ) { + if (!BBI->use_empty()) + BBI->replaceAllUsesWith(UndefValue::get(BBI->getType())); + BB->getInstList().erase(BBI++); + } + break; + } + + bool Changed = ConstantFoldTerminator(BB); for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) MarkAliveBlocks(*SI, Reachable); |