1 files changed, 33 insertions, 62 deletions

diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index 8e7c91a3f2..b49e14a810 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -518,7 +518,12 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
     std::swap(TrueDest, FalseDest);
 
   // Insert the new branch.
-  BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
+  BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
+
+  // If either edge is critical, split it. This helps preserve LoopSimplify
+  // form for enclosing loops.
+  SplitCriticalEdge(BI, 0, this);
+  SplitCriticalEdge(BI, 1, this);
 }
 
 /// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable
@@ -575,47 +580,11 @@ void LoopUnswitch::SplitExitEdges(Loop *L,
 
   for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
     BasicBlock *ExitBlock = ExitBlocks[i];
-    std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock));
-
-    for (unsigned j = 0, e = Preds.size(); j != e; ++j) {
-      BasicBlock* NewExitBlock = SplitEdge(Preds[j], ExitBlock, this);
-      BasicBlock* StartBlock = Preds[j];
-      BasicBlock* EndBlock;
-      if (NewExitBlock->getSinglePredecessor() == ExitBlock) {
-        EndBlock = NewExitBlock;
-        NewExitBlock = EndBlock->getSinglePredecessor();
-      } else {
-        EndBlock = ExitBlock;
-      }
-      
-      std::set<PHINode*> InsertedPHIs;
-      PHINode* OldLCSSA = 0;
-      for (BasicBlock::iterator I = EndBlock->begin();
-           (OldLCSSA = dyn_cast<PHINode>(I)); ++I) {
-        Value* OldValue = OldLCSSA->getIncomingValueForBlock(NewExitBlock);
-        PHINode* NewLCSSA = PHINode::Create(OldLCSSA->getType(),
-                                            OldLCSSA->getName() + ".us-lcssa",
-                                            NewExitBlock->getTerminator());
-        NewLCSSA->addIncoming(OldValue, StartBlock);
-        OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(NewExitBlock),
-                                   NewLCSSA);
-        InsertedPHIs.insert(NewLCSSA);
-      }
-
-      BasicBlock::iterator InsertPt = EndBlock->getFirstNonPHI();
-      for (BasicBlock::iterator I = NewExitBlock->begin();
-         (OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0;
-         ++I) {
-        PHINode *NewLCSSA = PHINode::Create(OldLCSSA->getType(),
-                                            OldLCSSA->getName() + ".us-lcssa",
-                                            InsertPt);
-        OldLCSSA->replaceAllUsesWith(NewLCSSA);
-        NewLCSSA->addIncoming(OldLCSSA, NewExitBlock);
-      }
-
-    }    
+    SmallVector<BasicBlock *, 4> Preds(pred_begin(ExitBlock),
+                                       pred_end(ExitBlock));
+    SplitBlockPredecessors(ExitBlock, Preds.data(), Preds.size(),
+                           ".us-lcssa", this);
   }
-
 }
 
 /// UnswitchNontrivialCondition - We determined that the loop is profitable 
@@ -945,27 +914,29 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
               // FIXME: This is a hack.  We need to keep the successor around
               // and hooked up so as to preserve the loop structure, because
               // trying to update it is complicated.  So instead we preserve the
-              // loop structure and put the block on an dead code path.
-              
-              BasicBlock *SISucc = SI->getSuccessor(i);
-              BasicBlock* Old = SI->getParent();
-              BasicBlock* Split = SplitBlock(Old, SI, this);
-              
-              Instruction* OldTerm = Old->getTerminator();
-              BranchInst::Create(Split, SISucc,
-                                 ConstantInt::getTrue(Context), OldTerm);
-
-              LPM->deleteSimpleAnalysisValue(Old->getTerminator(), L);
-              Old->getTerminator()->eraseFromParent();
-              
-              PHINode *PN;
-              for (BasicBlock::iterator II = SISucc->begin();
-                   (PN = dyn_cast<PHINode>(II)); ++II) {
-                Value *InVal = PN->removeIncomingValue(Split, false);
-                PN->addIncoming(InVal, Old);
-              }
-
-              SI->removeCase(i);
+              // loop structure and put the block on a dead code path.
+              BasicBlock *Switch = SI->getParent();
+              SplitEdge(Switch, SI->getSuccessor(i), this);
+              // Compute the successors instead of relying on the return value
+              // of SplitEdge, since it may have split the switch successor
+              // after PHI nodes.
+              BasicBlock *NewSISucc = SI->getSuccessor(i);
+              BasicBlock *OldSISucc = *succ_begin(NewSISucc);
+              // Create an "unreachable" destination.
+              BasicBlock *Abort = BasicBlock::Create(Context, "us-unreachable",
+                                                     Switch->getParent(),
+                                                     OldSISucc);
+              new UnreachableInst(Context, Abort);
+              // Force the new case destination to branch to the "unreachable"
+              // block while maintaining a (dead) CFG edge to the old block.
+              NewSISucc->getTerminator()->eraseFromParent();
+              BranchInst::Create(Abort, OldSISucc,
+                                 ConstantInt::getTrue(Context), NewSISucc);
+              // Release the PHI operands for this edge.
+              for (BasicBlock::iterator II = NewSISucc->begin();
+                   PHINode *PN = dyn_cast<PHINode>(II); ++II)
+                PN->setIncomingValue(PN->getBasicBlockIndex(Switch),
+                                     UndefValue::get(PN->getType()));
               break;
             }
           }