Rename DeadLoopElimination to LoopDeletion, part one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50436 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 260 deletions

diff --git a/lib/Transforms/Scalar/DeadLoopElimination.cpp b/lib/Transforms/Scalar/DeadLoopElimination.cpp
deleted file mode 100644
index fc11cab809..0000000000
--- a/lib/Transforms/Scalar/DeadLoopElimination.cpp
+++ /dev/null
@@ -1,260 +0,0 @@
-//===- DeadLoopElimination.cpp - Dead Loop Elimination Pass ---------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the Dead Loop Elimination Pass.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "dead-loop"
-
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Instruction.h"
-#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/LoopPass.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/SmallVector.h"
-
-using namespace llvm;
-
-STATISTIC(NumDeleted, "Number of loops deleted");
-
-namespace {
-  class VISIBILITY_HIDDEN DeadLoopElimination : public LoopPass {
-  public:
-    static char ID; // Pass ID, replacement for typeid
-    DeadLoopElimination() : LoopPass((intptr_t)&ID) { }
-    
-    // Possibly eliminate loop L if it is dead.
-    bool runOnLoop(Loop* L, LPPassManager& LPM);
-    
-    bool SingleDominatingExit(Loop* L);
-    bool IsLoopDead(Loop* L);
-    bool IsLoopInvariantInst(Instruction *I, Loop* L);
-    
-    virtual void getAnalysisUsage(AnalysisUsage& AU) const {
-      AU.addRequired<DominatorTree>();
-      AU.addRequired<LoopInfo>();
-      AU.addRequiredID(LoopSimplifyID);
-      AU.addRequiredID(LCSSAID);
-      
-      AU.addPreserved<DominatorTree>();
-      AU.addPreserved<LoopInfo>();
-      AU.addPreservedID(LoopSimplifyID);
-      AU.addPreservedID(LCSSAID);
-    }
-  };
-  
-  char DeadLoopElimination::ID = 0;
-  RegisterPass<DeadLoopElimination> X ("dead-loop", "Eliminate dead loops");
-}
-
-LoopPass* llvm::createDeadLoopEliminationPass() {
-  return new DeadLoopElimination();
-}
-
-bool DeadLoopElimination::SingleDominatingExit(Loop* L) {
-  SmallVector<BasicBlock*, 4> exitingBlocks;
-  L->getExitingBlocks(exitingBlocks);
-  
-  if (exitingBlocks.size() != 1)
-    return 0;
-  
-  BasicBlock* latch = L->getLoopLatch();
-  if (!latch)
-    return 0;
-  
-  DominatorTree& DT = getAnalysis<DominatorTree>();
-  if (DT.dominates(exitingBlocks[0], latch))
-    return exitingBlocks[0];
-  else
-    return 0;
-}
-
-bool DeadLoopElimination::IsLoopInvariantInst(Instruction *I, Loop* L)  {
-  // PHI nodes are not loop invariant if defined in  the loop.
-  if (isa<PHINode>(I) && L->contains(I->getParent()))
-    return false;
-    
-  // The instruction is loop invariant if all of its operands are loop-invariant
-  for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
-    if (!L->isLoopInvariant(I->getOperand(i)))
-      return false;
-
-  // If we got this far, the instruction is loop invariant!
-  return true;
-}
-
-bool DeadLoopElimination::IsLoopDead(Loop* L) {
-  SmallVector<BasicBlock*, 1> exitingBlocks;
-  L->getExitingBlocks(exitingBlocks);
-  BasicBlock* exitingBlock = exitingBlocks[0];
-    
-  // Get the set of out-of-loop blocks that the exiting block branches to.
-  SmallVector<BasicBlock*, 8> exitBlocks;
-  L->getUniqueExitBlocks(exitBlocks);
-  if (exitBlocks.size() > 1)
-    return false;
-  BasicBlock* exitBlock = exitBlocks[0];
-  
-  // Make sure that all PHI entries coming from the loop are loop invariant.
-  BasicBlock::iterator BI = exitBlock->begin();
-  while (PHINode* P = dyn_cast<PHINode>(BI)) {
-    Value* incoming = P->getIncomingValueForBlock(exitingBlock);
-    if (Instruction* I = dyn_cast<Instruction>(incoming))
-      if (!IsLoopInvariantInst(I, L))
-        return false;
-      
-    BI++;
-  }
-  
-  // Make sure that no instructions in the block have potential side-effects.
-  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
-       LI != LE; ++LI) {
-    for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
-         BI != BE; ++BI) {
-      if (BI->mayWriteToMemory())
-        return false;
-    }
-  }
-  
-  return true;
-}
-
-/// runOnLoop - Remove dead loops, by which we mean loops that do not impact the
-/// observable behavior of the program other than finite running time.  Note 
-/// we do ensure that this never remove a loop that might be infinite, as doing
-/// so could change the halting/non-halting nature of a program.
-bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
-  // Don't remove loops for which we can't solve the trip count.
-  // They could be infinite, in which case we'd be changing program behavior.
-  if (L->getTripCount())
-    return false;
-  
-  // We can only remove the loop if there is a preheader that we can 
-  // branch from after removing it.
-  BasicBlock* preheader = L->getLoopPreheader();
-  if (!preheader)
-    return false;
-  
-  // We can't remove loops that contain subloops.  If the subloops were dead,
-  // they would already have been removed in earlier executions of this pass.
-  if (L->begin() != L->end())
-    return false;
-  
-  // Loops with multiple exits or exits that don't dominate the latch
-  // are too complicated to handle correctly.
-  if (!SingleDominatingExit(L))
-    return false;
-  
-  // Finally, we have to check that the loop really is dead.
-  if (!IsLoopDead(L))
-    return false;
-  
-  // Now that we know the removal is safe, change the branch from the preheader
-  // to go to the single exiting block.
-  SmallVector<BasicBlock*, 1> exitingBlocks;
-  L->getExitingBlocks(exitingBlocks);
-  BasicBlock* exitingBlock = exitingBlocks[0];
-  
-  SmallVector<BasicBlock*, 1> exitBlocks;
-  L->getUniqueExitBlocks(exitBlocks);
-  BasicBlock* exitBlock = exitBlocks[0];
-  
-  // Because we're deleting a large chunk of code at once, the sequence in which
-  // we remove things is very important to avoid invalidation issues.  Don't
-  // mess with this unless you have good reason and know what you're doing.
-  
-  // Move simple loop-invariant expressions out of the loop, since they
-  // might be needed by the exit phis.
-  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
-       LI != LE; ++LI)
-    for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
-         BI != BE; ) {
-      Instruction* I = BI++;
-      if (I->getNumUses() > 0 && IsLoopInvariantInst(I, L))
-        I->moveBefore(preheader->getTerminator());
-    }
-  
-  // Connect the preheader directly to the exit block.
-  TerminatorInst* TI = preheader->getTerminator();
-  if (BranchInst* BI = dyn_cast<BranchInst>(TI)) {
-    if (BI->isUnconditional())
-      BI->setSuccessor(0, exitBlock);
-    else if (L->contains(BI->getSuccessor(0)))
-      BI->setSuccessor(0, exitBlock);
-    else
-      BI->setSuccessor(1, exitBlock);
-  } else {
-    // FIXME: Support switches
-    return false;
-  }
-  
-  // Rewrite phis in the exit block to get their inputs from
-  // the preheader instead of the exiting block.
-  BasicBlock::iterator BI = exitBlock->begin();
-  while (PHINode* P = dyn_cast<PHINode>(BI)) {
-    unsigned i = P->getBasicBlockIndex(exitingBlock);
-    P->setIncomingBlock(i, preheader);
-    BI++;
-  }
-  
-  // Update lots of internal structures...
-  DominatorTree& DT = getAnalysis<DominatorTree>();
-  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
-       LI != LE; ++LI) {
-    // Move all of the block's children to be children of the preheader, which
-    // allows us to remove the domtree entry for the block.
-    SmallPtrSet<DomTreeNode*, 8> childNodes;
-    childNodes.insert(DT[*LI]->begin(), DT[*LI]->end());
-    for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = childNodes.begin(),
-         DE = childNodes.end(); DI != DE; ++DI)
-      DT.changeImmediateDominator(*DI, DT[preheader]);
-    
-    DT.eraseNode(*LI);
-    
-    // Drop all references between the instructions and the block so
-    // that we don't have reference counting problems later.
-    for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
-         BI != BE; ++BI) {
-      BI->dropAllReferences();
-    }
-    
-    (*LI)->dropAllReferences();
-  }
-  
-  // Erase the instructions and the blocks without having to worry
-  // about ordering because we already dropped the references.
-  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
-       LI != LE; ++LI) {
-    for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
-         BI != BE; ) {
-      Instruction* I = BI++;
-      I->eraseFromParent();
-    }
-    
-    (*LI)->eraseFromParent();
-  }
-  
-  // Finally, the blocks from loopinfo.  This has to happen late because
-  // otherwise our loop iterators won't work.
-  LoopInfo& loopInfo = getAnalysis<LoopInfo>();
-  SmallPtrSet<BasicBlock*, 8> blocks;
-  blocks.insert(L->block_begin(), L->block_end());
-  for (SmallPtrSet<BasicBlock*,8>::iterator I = blocks.begin(),
-       E = blocks.end(); I != E; ++I)
-    loopInfo.removeBlock(*I);
-  
-  // The last step is to inform the loop pass manager that we've
-  // eliminated this loop.
-  LPM.deleteLoopFromQueue(L);
-  
-  NumDeleted++;
-  
-  return true;
-}