Update various Loop optimization passes to cope with the possibility that

LoopSimplify form may not be available.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86175 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/LoopExtractor.cpp

@@ -75,6 +75,10 @@ bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) {
   if (L->getParentLoop())
     return false;
 
+  // If LoopSimplify form is not available, stay out of trouble.
+  if (!L->isLoopSimplifyForm())
+    return false;
+
   DominatorTree &DT = getAnalysis<DominatorTree>();
   bool Changed = false;
 

lib/Transforms/Scalar/IndVarSimplify.cpp

@@ -536,8 +536,10 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
   BasicBlock *ExitBlock = L->getExitBlock();
   if (!ExitBlock) return;
 
-  Instruction *InsertPt = ExitBlock->getFirstNonPHI();
   BasicBlock *Preheader = L->getLoopPreheader();
+  if (!Preheader) return;
+
+  Instruction *InsertPt = ExitBlock->getFirstNonPHI();
   BasicBlock::iterator I = Preheader->getTerminator();
   while (I != Preheader->begin()) {
     --I;

lib/Transforms/Scalar/LICM.cpp

@@ -263,7 +263,6 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
 
   // Get the preheader block to move instructions into...
   Preheader = L->getLoopPreheader();
-  assert(Preheader&&"Preheader insertion pass guarantees we have a preheader!");
 
   // Loop over the body of this loop, looking for calls, invokes, and stores.
   // Because subloops have already been incorporated into AST, we skip blocks in
@@ -286,12 +285,14 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
   // us to sink instructions in one pass, without iteration.  After sinking
   // instructions, we perform another pass to hoist them out of the loop.
   //
-  SinkRegion(DT->getNode(L->getHeader()));
+  if (L->hasDedicatedExits())
-  HoistRegion(DT->getNode(L->getHeader()));
+    SinkRegion(DT->getNode(L->getHeader()));
+  if (Preheader)
+    HoistRegion(DT->getNode(L->getHeader()));
 
   // Now that all loop invariants have been removed from the loop, promote any
   // memory references to scalars that we can...
-  if (!DisablePromotion)
+  if (!DisablePromotion && Preheader && L->hasDedicatedExits())
     PromoteValuesInLoop();
 
   // Clear out loops state information for the next iteration

lib/Transforms/Scalar/LoopIndexSplit.cpp

@@ -209,6 +209,10 @@ bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
   L = IncomingLoop;
   LPM = &LPM_Ref;
 
+  // If LoopSimplify form is not available, stay out of trouble.
+  if (!L->isLoopSimplifyForm())
+    return false;
+
   // FIXME - Nested loops make dominator info updates tricky. 
   if (!L->getSubLoops().empty())
     return false;

lib/Transforms/Scalar/LoopRotation.cpp

@@ -104,17 +104,18 @@ bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) {
 bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
   L = Lp;
 
-  OrigHeader =  L->getHeader();
   OrigPreHeader = L->getLoopPreheader();
+  if (!OrigPreHeader) return false;
+
   OrigLatch = L->getLoopLatch();
+  if (!OrigLatch) return false;
+
+  OrigHeader =  L->getHeader();
 
   // If the loop has only one block then there is not much to rotate.
   if (L->getBlocks().size() == 1)
     return false;
 
-  assert(OrigHeader && OrigLatch && OrigPreHeader &&
-         "Loop is not in canonical form");
-
   // If the loop header is not one of the loop exiting blocks then
   // either this loop is already rotated or it is not
   // suitable for loop rotation transformations.

lib/Transforms/Scalar/LoopStrengthReduce.cpp

@@ -2528,6 +2528,10 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
   SE = &getAnalysis<ScalarEvolution>();
   Changed = false;
 
+  // If LoopSimplify form is not available, stay out of trouble.
+  if (!L->getLoopPreheader() || !L->getLoopLatch())
+    return false;
+
   if (!IU->IVUsesByStride.empty()) {
     DEBUG(errs() << "\nLSR on \"" << L->getHeader()->getParent()->getName()
           << "\" ";

lib/Transforms/Scalar/LoopUnswitch.cpp

@@ -407,6 +407,10 @@ bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val){
   initLoopData();
   Function *F = loopHeader->getParent();
 
+  // If LoopSimplify was unable to form a preheader, don't do any unswitching.
+  if (!loopPreheader)
+    return false;
+
   // If the condition is trivial, always unswitch.  There is no code growth for
   // this case.
   if (!IsTrivialUnswitchCondition(LoopCond)) {