1 files changed, 31 insertions, 11 deletions

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index 8795cd8..0192e92 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -175,7 +175,9 @@ namespace {
     bool canSinkOrHoistInst(Instruction &I);
     bool isNotUsedInLoop(Instruction &I);
 
-    void PromoteAliasSet(AliasSet &AS);
+    void PromoteAliasSet(AliasSet &AS,
+                         SmallVectorImpl<BasicBlock*> &ExitBlocks,
+                         SmallVectorImpl<Instruction*> &InsertPts);
   };
 }
 
@@ -256,10 +258,13 @@ bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
   // Now that all loop invariants have been removed from the loop, promote any
   // memory references to scalars that we can.
   if (!DisablePromotion && Preheader && L->hasDedicatedExits()) {
+    SmallVector<BasicBlock *, 8> ExitBlocks;
+    SmallVector<Instruction *, 8> InsertPts;
+
     // Loop over all of the alias sets in the tracker object.
     for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end();
          I != E; ++I)
-      PromoteAliasSet(*I);
+      PromoteAliasSet(*I, ExitBlocks, InsertPts);
   }
 
   // Clear out loops state information for the next iteration
@@ -618,6 +623,11 @@ bool LICM::isGuaranteedToExecute(Instruction &Inst) {
     if (!DT->dominates(Inst.getParent(), ExitBlocks[i]))
       return false;
 
+  // As a degenerate case, if the loop is statically infinite then we haven't
+  // proven anything since there are no exit blocks.
+  if (ExitBlocks.empty())
+    return false;
+
   return true;
 }
 
@@ -626,6 +636,7 @@ namespace {
     Value *SomePtr;  // Designated pointer to store to.
     SmallPtrSet<Value*, 4> &PointerMustAliases;
     SmallVectorImpl<BasicBlock*> &LoopExitBlocks;
+    SmallVectorImpl<Instruction*> &LoopInsertPts;
     AliasSetTracker &AST;
     DebugLoc DL;
     int Alignment;
@@ -633,11 +644,12 @@ namespace {
     LoopPromoter(Value *SP,
                  const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
                  SmallPtrSet<Value*, 4> &PMA,
-                 SmallVectorImpl<BasicBlock*> &LEB, AliasSetTracker &ast,
-                 DebugLoc dl, int alignment)
+                 SmallVectorImpl<BasicBlock*> &LEB,
+                 SmallVectorImpl<Instruction*> &LIP,
+                 AliasSetTracker &ast, DebugLoc dl, int alignment)
       : LoadAndStorePromoter(Insts, S), SomePtr(SP),
-        PointerMustAliases(PMA), LoopExitBlocks(LEB), AST(ast), DL(dl),
-        Alignment(alignment) {}
+        PointerMustAliases(PMA), LoopExitBlocks(LEB), LoopInsertPts(LIP),
+        AST(ast), DL(dl), Alignment(alignment) {}
 
     virtual bool isInstInList(Instruction *I,
                               const SmallVectorImpl<Instruction*> &) const {
@@ -657,7 +669,7 @@ namespace {
       for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
         BasicBlock *ExitBlock = LoopExitBlocks[i];
         Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
-        Instruction *InsertPos = ExitBlock->getFirstInsertionPt();
+        Instruction *InsertPos = LoopInsertPts[i];
         StoreInst *NewSI = new StoreInst(LiveInValue, SomePtr, InsertPos);
         NewSI->setAlignment(Alignment);
         NewSI->setDebugLoc(DL);
@@ -679,7 +691,9 @@ namespace {
 /// looping over the stores in the loop, looking for stores to Must pointers
 /// which are loop invariant.
 ///
-void LICM::PromoteAliasSet(AliasSet &AS) {
+void LICM::PromoteAliasSet(AliasSet &AS,
+                           SmallVectorImpl<BasicBlock*> &ExitBlocks,
+                           SmallVectorImpl<Instruction*> &InsertPts) {
   // We can promote this alias set if it has a store, if it is a "Must" alias
   // set, if the pointer is loop invariant, and if we are not eliminating any
   // volatile loads or stores.
@@ -789,14 +803,20 @@ void LICM::PromoteAliasSet(AliasSet &AS) {
   // location is better than none.
   DebugLoc DL = LoopUses[0]->getDebugLoc();
 
-  SmallVector<BasicBlock*, 8> ExitBlocks;
-  CurLoop->getUniqueExitBlocks(ExitBlocks);
+  // Figure out the loop exits and their insertion points, if this is the
+  // first promotion.
+  if (ExitBlocks.empty()) {
+    CurLoop->getUniqueExitBlocks(ExitBlocks);
+    InsertPts.resize(ExitBlocks.size());
+    for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
+      InsertPts[i] = ExitBlocks[i]->getFirstInsertionPt();
+  }
 
   // We use the SSAUpdater interface to insert phi nodes as required.
   SmallVector<PHINode*, 16> NewPHIs;
   SSAUpdater SSA(&NewPHIs);
   LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
-                        *CurAST, DL, Alignment);
+                        InsertPts, *CurAST, DL, Alignment);
 
   // Set up the preheader to have a definition of the value.  It is the live-out
   // value from the preheader that uses in the loop will use.