Index: lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- lib/Transforms/Scalar/LoopInterchange.cpp
+++ lib/Transforms/Scalar/LoopInterchange.cpp
@@ -1297,8 +1297,7 @@
     else
       InnerIndexVar = dyn_cast<Instruction>(InductionPHI->getIncomingValue(0));
 
-    // Ensure that InductionPHI is the first Phi node as required by
-    // splitInnerLoopHeader
+    // Ensure that InductionPHI is the first Phi node.
     if (&InductionPHI->getParent()->front() != InductionPHI)
       InductionPHI->moveBefore(&InductionPHI->getParent()->front());
 
@@ -1309,8 +1308,9 @@
     LLVM_DEBUG(dbgs() << "splitInnerLoopLatch done\n");
 
     // Splits the inner loops phi nodes out into a separate basic block.
-    splitInnerLoopHeader();
-    LLVM_DEBUG(dbgs() << "splitInnerLoopHeader done\n");
+    BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
+    SplitBlock(InnerLoopHeader, InnerLoopHeader->getFirstNonPHI(), DT, LI);
+    LLVM_DEBUG(dbgs() << "splitting InnerLoopHeader done\n");
   }
 
   Transformed |= adjustLoopLinks();
@@ -1328,32 +1328,7 @@
   InnerLoopLatch = SplitBlock(InnerLoopLatchPred, Inc, DT, LI);
 }
 
-void LoopInterchangeTransform::splitInnerLoopHeader() {
-  // Split the inner loop header out. Here make sure that the reduction PHI's
-  // stay in the innerloop body.
-  BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
-  BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
-  SplitBlock(InnerLoopHeader, InnerLoopHeader->getFirstNonPHI(), DT, LI);
-  if (InnerLoopHasReduction) {
-    // Adjust Reduction PHI's in the block. The induction PHI must be the first
-    // PHI in InnerLoopHeader for this to work.
-    SmallVector<PHINode *, 8> PHIVec;
-    for (auto I = std::next(InnerLoopHeader->begin()); isa<PHINode>(I); ++I) {
-      PHINode *PHI = dyn_cast<PHINode>(I);
-      Value *V = PHI->getIncomingValueForBlock(InnerLoopPreHeader);
-      PHI->replaceAllUsesWith(V);
-      PHIVec.push_back((PHI));
-    }
-    for (PHINode *P : PHIVec) {
-      P->eraseFromParent();
-    }
-  }
-
-  LLVM_DEBUG(dbgs() << "Output of splitInnerLoopHeader InnerLoopHeaderSucc & "
-                       "InnerLoopHeader\n");
-}
-
-/// Move all instructions except the terminator from FromBB right before
+/// \brief Move all instructions except the terminator from FromBB right before
 /// InsertBefore
 static void moveBBContents(BasicBlock *FromBB, Instruction *InsertBefore) {
   auto &ToList = InsertBefore->getParent()->getInstList();
@@ -1489,6 +1464,41 @@
   restructureLoops(OuterLoop, InnerLoop, InnerLoopPreHeader,
                    OuterLoopPreHeader);
 
+  // Now update the reduction PHIs in the inner and outer loop headers.
+  SmallVector<PHINode *, 4> InnerLoopPHIs, OuterLoopPHIs;
+  for (PHINode &PHI : drop_begin(InnerLoopHeader->phis(), 1))
+    InnerLoopPHIs.push_back(cast<PHINode>(&PHI));
+  for (PHINode &PHI : drop_begin(OuterLoopHeader->phis(), 1))
+    OuterLoopPHIs.push_back(cast<PHINode>(&PHI));
+
+  for (PHINode *PHI : OuterLoopPHIs)
+    PHI->moveBefore(InnerLoopHeader->getFirstNonPHI());
+
+  // Move the PHI nodes from the inner loop header to the outer loop header.
+  // We have to deal with one kind of PHI nodes:
+  //  1) PHI nodes that are part of inner loop-only reductions.
+  // We only have to move the PHI node and update the incoming blocks.
+  for (PHINode *PHI : InnerLoopPHIs) {
+    PHI->moveBefore(OuterLoopHeader->getFirstNonPHI());
+    for (BasicBlock *InBB : PHI->blocks()) {
+      if (InnerLoop->contains(InBB))
+        continue;
+
+      assert(isa<PHINode>(PHI->getIncomingValueForBlock(InBB)) &&
+             "Unexpected incoming PHI node, reductions in outer loop are not "
+             "supported yet");
+      PHI->replaceAllUsesWith(PHI->getIncomingValueForBlock(InBB));
+      PHI->eraseFromParent();
+      break;
+    }
+  }
+
+  // Update the incoming blocks for moved PHI nodes.
+  updateIncomingBlock(OuterLoopHeader, InnerLoopPreHeader, OuterLoopPreHeader);
+  updateIncomingBlock(OuterLoopHeader, InnerLoopLatch, OuterLoopLatch);
+  updateIncomingBlock(InnerLoopHeader, OuterLoopPreHeader, InnerLoopPreHeader);
+  updateIncomingBlock(InnerLoopHeader, OuterLoopLatch, InnerLoopLatch);
+
   return true;
 }