Move BreakCriticalEdges pass to lib/Transforms/Utils

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5754 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/BreakCriticalEdges.cpp b/lib/Transforms/Scalar/BreakCriticalEdges.cpp
deleted file mode 100644 (file)
index c44f9d3..0000000
--- a/lib/Transforms/Scalar/BreakCriticalEdges.cpp
+++ /dev/null
@@ -1,155 +0,0 @@
-//===- BreakCriticalEdges.cpp - Critical Edge Elimination Pass ------------===//
-//
-// BreakCriticalEdges pass - Break all of the critical edges in the CFG by
-// inserting a dummy basic block.  This pass may be "required" by passes that
-// cannot deal with critical edges.  For this usage, the structure type is
-// forward declared.  This pass obviously invalidates the CFG, but can update
-// forward dominator (set, immediate dominators, and tree) information.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Function.h"
-#include "llvm/iTerminators.h"
-#include "llvm/iPHINode.h"
-#include "llvm/Support/CFG.h"
-#include "Support/Statistic.h"
-
-namespace {
-  Statistic<> NumBroken("break-crit-edges", "Number of blocks inserted");
-
-  struct BreakCriticalEdges : public FunctionPass {
-    virtual bool runOnFunction(Function &F);
-    
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-      AU.addPreserved<DominatorSet>();
-      AU.addPreserved<ImmediateDominators>();
-      AU.addPreserved<DominatorTree>();
-      AU.addPreserved<DominanceFrontier>();
-      AU.addPreservedID(LoopPreheadersID);   // No preheaders deleted.
-    }
-  };
-
-  RegisterOpt<BreakCriticalEdges> X("break-crit-edges",
-                                    "Break critical edges in CFG");
-}
-
-// Publically exposed interface to pass...
-const PassInfo *BreakCriticalEdgesID = X.getPassInfo();
-Pass *createBreakCriticalEdgesPass() { return new BreakCriticalEdges(); }
-
-
-// isCriticalEdge - Return true if the specified edge is a critical edge.
-// Critical edges are edges from a block with multiple successors to a block
-// with multiple predecessors.
-//
-bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
-  assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!");
-  if (TI->getNumSuccessors() == 1) return false;
-
-  const BasicBlock *Dest = TI->getSuccessor(SuccNum);
-  pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest);
-
-  // If there is more than one predecessor, this is a critical edge...
-  assert(I != E && "No preds, but we have an edge to the block?");
-  ++I;        // Skip one edge due to the incoming arc from TI.
-  return I != E;
-}
-
-// SplitCriticalEdge - Insert a new node node to split the critical edge.  This
-// will update DominatorSet, ImmediateDominator and DominatorTree information if
-// it is available, thus calling this pass will not invalidate either of them.
-//
-void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
-  assert(isCriticalEdge(TI, SuccNum) &&
-         "Cannot break a critical edge, if it isn't a critical edge");
-  BasicBlock *TIBB = TI->getParent();
-  BasicBlock *DestBB = TI->getSuccessor(SuccNum);
-
-  // Create a new basic block, linking it into the CFG.
-  BasicBlock *NewBB = new BasicBlock(TIBB->getName() + "." +
-                                     DestBB->getName() + "_crit_edge");
-  // Create our unconditional branch...
-  BranchInst *BI = new BranchInst(DestBB);
-  NewBB->getInstList().push_back(BI);
-  
-  // Branch to the new block, breaking the edge...
-  TI->setSuccessor(SuccNum, NewBB);
-
-  // Insert the block into the function... right after the block TI lives in.
-  Function &F = *TIBB->getParent();
-  F.getBasicBlockList().insert(TIBB->getNext(), NewBB);
-
-  // If there are any PHI nodes in DestBB, we need to update them so that they
-  // merge incoming values from NewBB instead of from TIBB.
-  //
-  for (BasicBlock::iterator I = DestBB->begin();
-       PHINode *PN = dyn_cast<PHINode>(&*I); ++I) {
-    // We no longer enter through TIBB, now we come in through NewBB.
-    PN->replaceUsesOfWith(TIBB, NewBB);
-  }
-
-  // If we don't have a pass object, we can't update anything...
-  if (P == 0) return;
-
-  // Now update analysis information.  These are the analyses that we are
-  // currently capable of updating...
-  //
-
-  // Should we update DominatorSet information?
-  if (DominatorSet *DS = P->getAnalysisToUpdate<DominatorSet>()) {
-    // The blocks that dominate the new one are the blocks that dominate TIBB
-    // plus the new block itself.
-    DominatorSet::DomSetType DomSet = DS->getDominators(TIBB);
-    DomSet.insert(NewBB);  // A block always dominates itself.
-    DS->addBasicBlock(NewBB, DomSet);
-  }
-
-  // Should we update ImmdediateDominator information?
-  if (ImmediateDominators *ID = P->getAnalysisToUpdate<ImmediateDominators>()) {
-    // TIBB is the new immediate dominator for NewBB.  NewBB doesn't dominate
-    // anything.
-    ID->addNewBlock(NewBB, TIBB);
-  }
-  
-  // Should we update DominatorTree information?
-  if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
-    DominatorTree::Node *TINode = DT->getNode(TIBB);
-    
-    // The new block is not the immediate dominator for any other nodes, but
-    // TINode is the immediate dominator for the new node.
-    //
-    if (TINode)        // Don't break unreachable code!
-      DT->createNewNode(NewBB, TINode);
-  }
-
-  // Should we update DominanceFrontier information?
-  if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>()) {
-    // Since the new block is dominated by its only predecessor TIBB,
-    // it cannot be in any block's dominance frontier.  Its dominance
-    // frontier is {DestBB}.
-    DominanceFrontier::DomSetType NewDFSet;
-    NewDFSet.insert(DestBB);
-    DF->addBasicBlock(NewBB, NewDFSet);
-  }
-}
-
-// runOnFunction - Loop over all of the edges in the CFG, breaking critical
-// edges as they are found.
-//
-bool BreakCriticalEdges::runOnFunction(Function &F) {
-  bool Changed = false;
-  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
-    TerminatorInst *TI = I->getTerminator();
-    if (TI->getNumSuccessors() > 1)
-      for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
-        if (isCriticalEdge(TI, i)) {
-          SplitCriticalEdge(TI, i, this);
-          ++NumBroken;
-          Changed = true;
-        }
-  }
-
-  return Changed;
-}