diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp deleted file mode 100644 index 665d538ef9a..00000000000 --- a/lib/Transforms/Scalar/DeadStoreElimination.cpp +++ /dev/null @@ -1,179 +0,0 @@ -//===- DeadStoreElimination.cpp - Dead Store Elimination ------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file was developed by the LLVM research group and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements a trivial dead store elimination that only considers -// basic-block local redundant stores. -// -// FIXME: This should eventually be extended to be a post-dominator tree -// traversal. Doing so would be pretty trivial. -// -//===----------------------------------------------------------------------===// - -#define DEBUG_TYPE "dse" -#include "llvm/Transforms/Scalar.h" -#include "llvm/DerivedTypes.h" -#include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Analysis/AliasSetTracker.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/Support/Compiler.h" -using namespace llvm; - -STATISTIC(NumStores, "Number of stores deleted"); -STATISTIC(NumOther , "Number of other instrs removed"); - -namespace { - struct VISIBILITY_HIDDEN DSE : public FunctionPass { - static char ID; // Pass identification, replacement for typeid - DSE() : FunctionPass((intptr_t)&ID) {} - - virtual bool runOnFunction(Function &F) { - bool Changed = false; - for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) - Changed |= runOnBasicBlock(*I); - return Changed; - } - - bool runOnBasicBlock(BasicBlock &BB); - - void DeleteDeadInstructionChains(Instruction *I, - SetVector &DeadInsts); - - // getAnalysisUsage - We require post dominance frontiers (aka Control - // Dependence Graph) - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.setPreservesCFG(); - AU.addRequired(); - AU.addRequired(); - AU.addPreserved(); - } - }; - char DSE::ID = 0; - RegisterPass X("dse", "Dead Store Elimination"); -} - -FunctionPass *llvm::createDeadStoreEliminationPass() { return new DSE(); } - -bool DSE::runOnBasicBlock(BasicBlock &BB) { - TargetData &TD = getAnalysis(); - AliasAnalysis &AA = getAnalysis(); - AliasSetTracker KillLocs(AA); - - // If this block ends in a return, unwind, unreachable, and eventually - // tailcall, then all allocas are dead at its end. - if (BB.getTerminator()->getNumSuccessors() == 0) { - BasicBlock *Entry = BB.getParent()->begin(); - for (BasicBlock::iterator I = Entry->begin(), E = Entry->end(); I != E; ++I) - if (AllocaInst *AI = dyn_cast(I)) { - unsigned Size = ~0U; - if (!AI->isArrayAllocation() && - AI->getType()->getElementType()->isSized()) - Size = (unsigned)TD.getTypeSize(AI->getType()->getElementType()); - KillLocs.add(AI, Size); - } - } - - // PotentiallyDeadInsts - Deleting dead stores from the program can make other - // instructions die if they were only used as operands to stores. Keep track - // of the operands to stores so that we can try deleting them at the end of - // the traversal. - SetVector PotentiallyDeadInsts; - - bool MadeChange = false; - for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ) { - Instruction *I = --BBI; // Keep moving iterator backwards - - // If this is a free instruction, it makes the free'd location dead! - if (FreeInst *FI = dyn_cast(I)) { - // Free instructions make any stores to the free'd location dead. - KillLocs.add(FI); - continue; - } - - if (!isa(I) || cast(I)->isVolatile()) { - // If this is a vaarg instruction, it reads its operand. We don't model - // it correctly, so just conservatively remove all entries. - if (isa(I)) { - KillLocs.clear(); - continue; - } - - // If this is a non-store instruction, it makes everything referenced no - // longer killed. Remove anything aliased from the alias set tracker. - KillLocs.remove(I); - continue; - } - - // If this is a non-volatile store instruction, and if it is already in - // the stored location is already in the tracker, then this is a dead - // store. We can just delete it here, but while we're at it, we also - // delete any trivially dead expression chains. - unsigned ValSize = (unsigned)TD.getTypeSize(I->getOperand(0)->getType()); - Value *Ptr = I->getOperand(1); - - if (AliasSet *AS = KillLocs.getAliasSetForPointerIfExists(Ptr, ValSize)) - for (AliasSet::iterator ASI = AS->begin(), E = AS->end(); ASI != E; ++ASI) - if (ASI.getSize() >= ValSize && // Overwriting all of this store. - AA.alias(ASI.getPointer(), ASI.getSize(), Ptr, ValSize) - == AliasAnalysis::MustAlias) { - // If we found a must alias in the killed set, then this store really - // is dead. Remember that the various operands of the store now have - // fewer users. At the end we will see if we can delete any values - // that are dead as part of the store becoming dead. - if (Instruction *Op = dyn_cast(I->getOperand(0))) - PotentiallyDeadInsts.insert(Op); - if (Instruction *Op = dyn_cast(Ptr)) - PotentiallyDeadInsts.insert(Op); - - // Delete it now. - ++BBI; // Don't invalidate iterator. - BB.getInstList().erase(I); // Nuke the store! - ++NumStores; - MadeChange = true; - goto BigContinue; - } - - // Otherwise, this is a non-dead store just add it to the set of dead - // locations. - KillLocs.add(cast(I)); - BigContinue:; - } - - while (!PotentiallyDeadInsts.empty()) { - Instruction *I = PotentiallyDeadInsts.back(); - PotentiallyDeadInsts.pop_back(); - DeleteDeadInstructionChains(I, PotentiallyDeadInsts); - } - return MadeChange; -} - -void DSE::DeleteDeadInstructionChains(Instruction *I, - SetVector &DeadInsts) { - // Instruction must be dead. - if (!I->use_empty() || !isInstructionTriviallyDead(I)) return; - - // Let the alias analysis know that we have nuked a value. - getAnalysis().deleteValue(I); - - // See if this made any operands dead. We do it this way in case the - // instruction uses the same operand twice. We don't want to delete a - // value then reference it. - for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { - if (Instruction *Op = dyn_cast(I->getOperand(i))) - DeadInsts.insert(Op); // Attempt to nuke it later. - I->setOperand(i, 0); // Drop from the operand list. - } - - I->eraseFromParent(); - ++NumOther; -}