1 files changed, 12 insertions, 18 deletions

diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 0c900ff..9afe428 100644
--- a/contrib/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -77,7 +77,6 @@ namespace {
     bool redoLoop;
 
     Loop *currentLoop;
-    DominanceFrontier *DF;
     DominatorTree *DT;
     BasicBlock *loopHeader;
     BasicBlock *loopPreheader;
@@ -92,15 +91,15 @@ namespace {
   public:
     static char ID; // Pass ID, replacement for typeid
     explicit LoopUnswitch(bool Os = false) : 
-      LoopPass(&ID), OptimizeForSize(Os), redoLoop(false), 
-      currentLoop(NULL), DF(NULL), DT(NULL), loopHeader(NULL),
+      LoopPass(ID), OptimizeForSize(Os), redoLoop(false), 
+      currentLoop(NULL), DT(NULL), loopHeader(NULL),
       loopPreheader(NULL) {}
 
     bool runOnLoop(Loop *L, LPPassManager &LPM);
     bool processCurrentLoop();
 
     /// This transformation requires natural loop information & requires that
-    /// loop preheaders be inserted into the CFG...
+    /// loop preheaders be inserted into the CFG.
     ///
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.addRequiredID(LoopSimplifyID);
@@ -110,7 +109,6 @@ namespace {
       AU.addRequiredID(LCSSAID);
       AU.addPreservedID(LCSSAID);
       AU.addPreserved<DominatorTree>();
-      AU.addPreserved<DominanceFrontier>();
     }
 
   private:
@@ -160,7 +158,7 @@ namespace {
   };
 }
 char LoopUnswitch::ID = 0;
-static RegisterPass<LoopUnswitch> X("loop-unswitch", "Unswitch loops");
+INITIALIZE_PASS(LoopUnswitch, "loop-unswitch", "Unswitch loops", false, false);
 
 Pass *llvm::createLoopUnswitchPass(bool Os) { 
   return new LoopUnswitch(Os); 
@@ -201,7 +199,6 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) {
 bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
   LI = &getAnalysis<LoopInfo>();
   LPM = &LPM_Ref;
-  DF = getAnalysisIfAvailable<DominanceFrontier>();
   DT = getAnalysisIfAvailable<DominatorTree>();
   currentLoop = L;
   Function *F = currentLoop->getHeader()->getParent();
@@ -216,8 +213,6 @@ bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
     // FIXME: Reconstruct dom info, because it is not preserved properly.
     if (DT)
       DT->runOnFunction(*F);
-    if (DF)
-      DF->runOnFunction(*F);
   }
   return Changed;
 }
@@ -282,19 +277,18 @@ bool LoopUnswitch::processCurrentLoop() {
   return Changed;
 }
 
-/// isTrivialLoopExitBlock - Check to see if all paths from BB either:
-///   1. Exit the loop with no side effects.
-///   2. Branch to the latch block with no side-effects.
+/// isTrivialLoopExitBlock - Check to see if all paths from BB exit the
+/// loop with no side effects (including infinite loops).
 ///
-/// If these conditions are true, we return true and set ExitBB to the block we
+/// If true, we return true and set ExitBB to the block we
 /// exit through.
 ///
 static bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB,
                                          BasicBlock *&ExitBB,
                                          std::set<BasicBlock*> &Visited) {
   if (!Visited.insert(BB).second) {
-    // Already visited and Ok, end of recursion.
-    return true;
+    // Already visited. Without more analysis, this could indicate an infinte loop.
+    return false;
   } else if (!L->contains(BB)) {
     // Otherwise, this is a loop exit, this is fine so long as this is the
     // first exit.
@@ -324,7 +318,7 @@ static bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB,
 /// process.  If so, return the block that is exited to, otherwise return null.
 static BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) {
   std::set<BasicBlock*> Visited;
-  Visited.insert(L->getHeader());  // Branches to header are ok.
+  Visited.insert(L->getHeader());  // Branches to header make infinite loops.
   BasicBlock *ExitBB = 0;
   if (isTrivialLoopExitBlockHelper(L, BB, ExitBB, Visited))
     return ExitBB;
@@ -356,8 +350,8 @@ bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val,
     if (!BI->isConditional() || BI->getCondition() != Cond)
       return false;
   
-    // Check to see if a successor of the branch is guaranteed to go to the
-    // latch block or exit through a one exit block without having any 
+    // Check to see if a successor of the branch is guaranteed to 
+    // exit through a unique exit block without having any 
     // side-effects.  If so, determine the value of Cond that causes it to do
     // this.
     if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop,