1 files changed, 27 insertions, 7 deletions

diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 16c4a15..65acc1d 100644
--- a/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -35,7 +35,7 @@ namespace {
   class LoopRotate : public LoopPass {
   public:
     static char ID; // Pass ID, replacement for typeid
-    LoopRotate() : LoopPass(&ID) {}
+    LoopRotate() : LoopPass(ID) {}
 
     // Rotate Loop L as many times as possible. Return true if
     // loop is rotated at least once.
@@ -43,15 +43,15 @@ namespace {
 
     // LCSSA form makes instruction renaming easier.
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreserved<DominatorTree>();
+      AU.addPreserved<DominanceFrontier>();
+      AU.addRequired<LoopInfo>();
+      AU.addPreserved<LoopInfo>();
       AU.addRequiredID(LoopSimplifyID);
       AU.addPreservedID(LoopSimplifyID);
       AU.addRequiredID(LCSSAID);
       AU.addPreservedID(LCSSAID);
       AU.addPreserved<ScalarEvolution>();
-      AU.addRequired<LoopInfo>();
-      AU.addPreserved<LoopInfo>();
-      AU.addPreserved<DominatorTree>();
-      AU.addPreserved<DominanceFrontier>();
     }
 
     // Helper functions
@@ -79,7 +79,7 @@ namespace {
 }
   
 char LoopRotate::ID = 0;
-static RegisterPass<LoopRotate> X("loop-rotate", "Rotate Loops");
+INITIALIZE_PASS(LoopRotate, "loop-rotate", "Rotate Loops", false, false);
 
 Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
 
@@ -221,7 +221,7 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
 
     // The value now exits in two versions: the initial value in the preheader
     // and the loop "next" value in the original header.
-    SSA.Initialize(OrigHeaderVal);
+    SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
     SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
     SSA.AddAvailableValue(OrigPreHeader, OrigPreHeaderVal);
 
@@ -261,6 +261,26 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
   // NewHeader is now the header of the loop.
   L->moveToHeader(NewHeader);
 
+  // Move the original header to the bottom of the loop, where it now more
+  // naturally belongs. This isn't necessary for correctness, and CodeGen can
+  // usually reorder blocks on its own to fix things like this up, but it's
+  // still nice to keep the IR readable.
+  //
+  // The original header should have only one predecessor at this point, since
+  // we checked that the loop had a proper preheader and unique backedge before
+  // we started.
+  assert(OrigHeader->getSinglePredecessor() &&
+         "Original loop header has too many predecessors after loop rotation!");
+  OrigHeader->moveAfter(OrigHeader->getSinglePredecessor());
+
+  // Also, since this original header only has one predecessor, zap its
+  // PHI nodes, which are now trivial.
+  FoldSingleEntryPHINodes(OrigHeader);
+
+  // TODO: We could just go ahead and merge OrigHeader into its predecessor
+  // at this point, if we don't mind updating dominator info.
+
+  // Establish a new preheader, update dominators, etc.
   preserveCanonicalLoopForm(LPM);
 
   ++NumRotated;