Index: llvm/lib/Analysis/IVDescriptors.cpp
===================================================================
--- llvm/lib/Analysis/IVDescriptors.cpp
+++ llvm/lib/Analysis/IVDescriptors.cpp
@@ -1299,6 +1299,26 @@
   return nullptr;
 }
 
+// Check that the loop has a unique entry value and a unique backedge value and
+// initialize StartValue and BEValue with these values from the Phi.
+static bool getStartAndBEValues(Value *&StartValue, Value *&BEValue,
+                                const Loop *TheLoop, PHINode *Phi) {
+  // We can analyze this phi if it has a unique entry value and a unique
+  // backedge value.
+  if (Phi->getNumIncomingValues() != 2)
+    return false;
+  if (TheLoop->contains(Phi->getIncomingBlock(0))) {
+    BEValue = Phi->getIncomingValue(0);
+    StartValue = Phi->getIncomingValue(1);
+  } else {
+    assert(TheLoop->contains(Phi->getIncomingBlock(1)) &&
+           "Unexpected Phi node in the loop");
+    BEValue = Phi->getIncomingValue(1);
+    StartValue = Phi->getIncomingValue(0);
+  }
+  return true;
+}
+
 bool InductionDescriptor::isFPInductionPHI(PHINode *Phi, const Loop *TheLoop,
                                            ScalarEvolution *SE,
                                            InductionDescriptor &D) {
@@ -1314,16 +1334,8 @@
   if (Phi->getNumIncomingValues() != 2)
     return false;
   Value *BEValue = nullptr, *StartValue = nullptr;
-  if (TheLoop->contains(Phi->getIncomingBlock(0))) {
-    BEValue = Phi->getIncomingValue(0);
-    StartValue = Phi->getIncomingValue(1);
-  } else {
-    assert(TheLoop->contains(Phi->getIncomingBlock(1)) &&
-           "Unexpected Phi node in the loop");
-    BEValue = Phi->getIncomingValue(1);
-    StartValue = Phi->getIncomingValue(0);
-  }
-
+  if (!getStartAndBEValues(StartValue, BEValue, TheLoop, Phi))
+    return false;
   BinaryOperator *BOp = dyn_cast<BinaryOperator>(BEValue);
   if (!BOp)
     return false;
@@ -1505,6 +1517,10 @@
     PHINode *Phi, const Loop *TheLoop, ScalarEvolution *SE,
     InductionDescriptor &D, const SCEV *Expr,
     SmallVectorImpl<Instruction *> *CastsToIgnore) {
+
+  if (TheLoop->getHeader() != Phi->getParent())
+    return false;
+
   Type *PhiTy = Phi->getType();
   // We only handle integer and pointer inductions variables.
   if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
@@ -1527,8 +1543,9 @@
     return false;
   }
 
-  Value *StartValue =
-      Phi->getIncomingValueForBlock(AR->getLoop()->getLoopPreheader());
+  Value *BEValue = nullptr, *StartValue = nullptr;
+  if (!getStartAndBEValues(StartValue, BEValue, TheLoop, Phi))
+    return false;
 
   BasicBlock *Latch = AR->getLoop()->getLoopLatch();
   if (!Latch)
Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1243,20 +1243,6 @@
   return true;
 }
 
-/// Checks if it is safe to call InductionDescriptor::isInductionPHI for \p Phi,
-/// and returns true if this Phi is an induction phi in the loop. When
-/// isInductionPHI returns true, \p ID will be also be set by isInductionPHI.
-static bool checkIsIndPhi(PHINode *Phi, Loop *L, ScalarEvolution *SE,
-                          InductionDescriptor &ID) {
-  if (!Phi)
-    return false;
-  if (!L->getLoopPreheader())
-    return false;
-  if (Phi->getParent() != L->getHeader())
-    return false;
-  return InductionDescriptor::isInductionPHI(Phi, L, SE, ID);
-}
-
 int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
                                 ScalarEvolution *SE,
                                 const TargetTransformInfo *TTI,
@@ -1317,7 +1303,7 @@
           InductionDescriptor ID;
           PHINode *IndPhi = dyn_cast<PHINode>(Inst);
           if (IndPhi) {
-            if (!checkIsIndPhi(IndPhi, L, SE, ID))
+            if (!InductionDescriptor::isInductionPHI(IndPhi, L, SE, ID))
               continue;
             // This is an induction PHI. Check that the only users are PHI
             // nodes, and induction variable update binary operators.
@@ -1338,7 +1324,9 @@
               continue;
             if (llvm::any_of(Inst->users(), [&](User *U) {
                   PHINode *Phi = dyn_cast<PHINode>(U);
-                  if (Phi != PN && !checkIsIndPhi(Phi, L, SE, ID))
+                  if (!Phi)
+                    return true;
+                  if (Phi != PN && !InductionDescriptor::isInductionPHI(Phi, L, SE, ID))
                     return true;
                   return false;
                 }))