diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 55dd09846e..e2ef04ea1d 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -45,9 +45,9 @@ #include "llvm/Support/CallSite.h" #include "llvm/Support/Debug.h" #include "llvm/Support/GetElementPtrTypeIterator.h" -#include "llvm/Support/InstIterator.h" #include "llvm/Support/InstVisitor.h" #include "llvm/Support/PatternMatch.h" +#include "llvm/ADT/DepthFirstIterator.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include <algorithm> @@ -4400,7 +4400,8 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) { // However, because we don't have dom info, we can't do a perfect job. if (Instruction *I = dyn_cast<Instruction>(V)) { // We know that the instruction dominates the PHI if there are no undef - // values coming in. + // values coming in. If the instruction is defined in the entry block, + // and is not an invoke, we know it is ok. if (I->getParent() != &I->getParent()->getParent()->front() || isa<InvokeInst>(I)) for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) @@ -5226,9 +5227,32 @@ bool InstCombiner::runOnFunction(Function &F) { bool Changed = false; TD = &getAnalysis<TargetData>(); - for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i) - WorkList.push_back(&*i); - + { + // Populate the worklist with the reachable instructions. + std::set<BasicBlock*> Visited; + for (df_ext_iterator<BasicBlock*> BB = df_ext_begin(&F.front(), Visited), + E = df_ext_end(&F.front(), Visited); BB != E; ++BB) + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) + WorkList.push_back(I); + + // Do a quick scan over the function. If we find any blocks that are + // unreachable, remove any instructions inside of them. This prevents + // the instcombine code from having to deal with some bad special cases. + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) + if (!Visited.count(BB)) { + Instruction *Term = BB->getTerminator(); + while (Term != BB->begin()) { // Remove instrs bottom-up + BasicBlock::iterator I = Term; --I; + + DEBUG(std::cerr << "IC: DCE: " << *I); + ++NumDeadInst; + + if (!I->use_empty()) + I->replaceAllUsesWith(UndefValue::get(I->getType())); + I->eraseFromParent(); + } + } + } while (!WorkList.empty()) { Instruction *I = WorkList.back(); // Get an instruction from the worklist |