Index: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -173,6 +173,7 @@
   const DataLayout &DL;
   SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
   const SimplifyCFGOptions &Options;
+  bool Resimplify;
 
   Value *isValueEqualityComparison(TerminatorInst *TI);
   BasicBlock *GetValueEqualityComparisonCases(
@@ -194,6 +195,9 @@
   bool SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder);
   bool SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder);
 
+  bool tryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
+                                             IRBuilder<> &Builder);
+
 public:
   SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout &DL,
                  SmallPtrSetImpl<BasicBlock *> *LoopHeaders,
@@ -201,6 +205,13 @@
       : TTI(TTI), DL(DL), LoopHeaders(LoopHeaders), Options(Opts) {}
 
   bool run(BasicBlock *BB);
+  bool simplifyOnce(BasicBlock *BB);
+
+  // Helper to set Resimplify and return change indication.
+  bool requestResimplify() {
+    Resimplify = true;
+    return true;
+  }
 };
 
 } // end anonymous namespace
@@ -3543,9 +3554,8 @@
 ///
 /// We prefer to split the edge to 'end' so that there is a true/false entry to
 /// the PHI, merging the third icmp into the switch.
-static bool tryToSimplifyUncondBranchWithICmpInIt(
-    ICmpInst *ICI, IRBuilder<> &Builder, const DataLayout &DL,
-    const TargetTransformInfo &TTI, const SimplifyCFGOptions &Options) {
+bool SimplifyCFGOpt::tryToSimplifyUncondBranchWithICmpInIt(
+    ICmpInst *ICI, IRBuilder<> &Builder) {
   BasicBlock *BB = ICI->getParent();
 
   // If the block has any PHIs in it or the icmp has multiple uses, it is too
@@ -3580,7 +3590,7 @@
       ICI->eraseFromParent();
     }
     // BB is now empty, so it is likely to simplify away.
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
   }
 
   // Ok, the block is reachable from the default dest.  If the constant we're
@@ -3596,7 +3606,7 @@
     ICI->replaceAllUsesWith(V);
     ICI->eraseFromParent();
     // BB is now empty, so it is likely to simplify away.
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
   }
 
   // The use of the icmp has to be in the 'end' block, by the only PHI node in
@@ -5595,33 +5605,33 @@
     // see if that predecessor totally determines the outcome of this switch.
     if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
       if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
 
     Value *Cond = SI->getCondition();
     if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
       if (SimplifySwitchOnSelect(SI, Select))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
 
     // If the block only contains the switch, see if we can fold the block
     // away into any preds.
     if (SI == &*BB->instructionsWithoutDebug().begin())
       if (FoldValueComparisonIntoPredecessors(SI, Builder))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
   }
 
   // Try to transform the switch into an icmp and a branch.
   if (TurnSwitchRangeIntoICmp(SI, Builder))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   // Remove unreachable cases.
   if (eliminateDeadSwitchCases(SI, Options.AC, DL))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   if (switchToSelect(SI, Builder, DL, TTI))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   if (Options.ForwardSwitchCondToPhi && ForwardSwitchConditionToPHI(SI))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   // The conversion from switch to lookup tables results in difficult-to-analyze
   // code and makes pruning branches much harder. This is a problem if the
@@ -5630,10 +5640,10 @@
   // optimisation pipeline.
   if (Options.ConvertSwitchToLookupTable &&
       SwitchToLookupTable(SI, Builder, DL, TTI))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   if (ReduceSwitchRange(SI, Builder, DL, TTI))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   return false;
 }
@@ -5671,7 +5681,7 @@
 
   if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) {
     if (SimplifyIndirectBrOnSelect(IBI, SI))
-      return simplifyCFG(BB, TTI, Options) || true;
+      return requestResimplify();
   }
   return Changed;
 }
@@ -5781,7 +5791,7 @@
       for (++I; isa<DbgInfoIntrinsic>(I); ++I)
         ;
       if (I->isTerminator() &&
-          tryToSimplifyUncondBranchWithICmpInIt(ICI, Builder, DL, TTI, Options))
+          tryToSimplifyUncondBranchWithICmpInIt(ICI, Builder))
         return true;
     }
 
@@ -5799,7 +5809,7 @@
   // predecessor and use logical operations to update the incoming value
   // for PHI nodes in common successor.
   if (FoldBranchToCommonDest(BI, Options.BonusInstThreshold))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
   return false;
 }
 
@@ -5827,18 +5837,18 @@
     // switch.
     if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
       if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
 
     // This block must be empty, except for the setcond inst, if it exists.
     // Ignore dbg intrinsics.
     auto I = BB->instructionsWithoutDebug().begin();
     if (&*I == BI) {
       if (FoldValueComparisonIntoPredecessors(BI, Builder))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
     } else if (&*I == cast<Instruction>(BI->getCondition())) {
       ++I;
       if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
     }
   }
 
@@ -5865,7 +5875,7 @@
                               : ConstantInt::getFalse(BB->getContext());
         BI->setCondition(CI);
         RecursivelyDeleteTriviallyDeadInstructions(OldCond);
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
       }
     }
   }
@@ -5874,7 +5884,7 @@
   // branches to us and one of our successors, fold the comparison into the
   // predecessor and use logical operations to pick the right destination.
   if (FoldBranchToCommonDest(BI, Options.BonusInstThreshold))
-    return simplifyCFG(BB, TTI, Options) || true;
+    return requestResimplify();
 
   // We have a conditional branch to two blocks that are only reachable
   // from BI.  We know that the condbr dominates the two blocks, so see if
@@ -5883,7 +5893,7 @@
   if (BI->getSuccessor(0)->getSinglePredecessor()) {
     if (BI->getSuccessor(1)->getSinglePredecessor()) {
       if (HoistThenElseCodeToIf(BI, TTI))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
     } else {
       // If Successor #1 has multiple preds, we may be able to conditionally
       // execute Successor #0 if it branches to Successor #1.
@@ -5891,7 +5901,7 @@
       if (Succ0TI->getNumSuccessors() == 1 &&
           Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
         if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), TTI))
-          return simplifyCFG(BB, TTI, Options) || true;
+          return requestResimplify();
     }
   } else if (BI->getSuccessor(1)->getSinglePredecessor()) {
     // If Successor #0 has multiple preds, we may be able to conditionally
@@ -5900,7 +5910,7 @@
     if (Succ1TI->getNumSuccessors() == 1 &&
         Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
       if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), TTI))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
   }
 
   // If this is a branch on a phi node in the current block, thread control
@@ -5908,14 +5918,14 @@
   if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
     if (PN->getParent() == BI->getParent())
       if (FoldCondBranchOnPHI(BI, DL, Options.AC))
-        return simplifyCFG(BB, TTI, Options) || true;
+        return requestResimplify();
 
   // Scan predecessor blocks for conditional branches.
   for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
     if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
       if (PBI != BI && PBI->isConditional())
         if (SimplifyCondBranchToCondBranch(PBI, BI, DL))
-          return simplifyCFG(BB, TTI, Options) || true;
+          return requestResimplify();
 
   // Look for diamond patterns.
   if (MergeCondStores)
@@ -5923,7 +5933,7 @@
       if (BranchInst *PBI = dyn_cast<BranchInst>(PrevBB->getTerminator()))
         if (PBI != BI && PBI->isConditional())
           if (mergeConditionalStores(PBI, BI, DL))
-            return simplifyCFG(BB, TTI, Options) || true;
+            return requestResimplify();
 
   return false;
 }
@@ -6006,7 +6016,7 @@
   return false;
 }
 
-bool SimplifyCFGOpt::run(BasicBlock *BB) {
+bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
   bool Changed = false;
 
   assert(BB && BB->getParent() && "Block not embedded in function!");
@@ -6080,6 +6090,21 @@
   return Changed;
 }
 
+bool SimplifyCFGOpt::run(BasicBlock *BB) {
+  bool Changed = false;
+
+  // Repeated simplify BB as long as resimplification is requested.
+  do {
+    Resimplify = false;
+
+    // Perform one round of simplifcation. Resimplify flag will be set if
+    // another iteration is requested.
+    Changed |= simplifyOnce(BB);
+  } while (Resimplify);
+
+  return Changed;
+}
+
 bool llvm::simplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
                        const SimplifyCFGOptions &Options,
                        SmallPtrSetImpl<BasicBlock *> *LoopHeaders) {