Index: llvm/lib/Transforms/Scalar/LoopDeletion.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopDeletion.cpp
+++ llvm/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -248,20 +248,22 @@
   // Check if there is only one predecessor on 1st iteration. Note that because
   // we iterate in RPOT, we have already visited all its (non-latch)
   // predecessors.
-  auto GetSolePredecessorOnFirstIteration = [&](BasicBlock * BB)->BasicBlock * {
+  auto GetSoleInputOnFirstIteration = [&](PHINode & PN)->Value * {
+    BasicBlock *BB = PN.getParent();
     if (BB == Header)
-      return L->getLoopPredecessor();
-    BasicBlock *OnlyPred = nullptr;
+      return PN.getIncomingValueForBlock(L->getLoopPredecessor());
+    Value *OnlyInput = nullptr;
     for (auto *Pred : predecessors(BB))
-      if (OnlyPred != Pred && LiveEdges.count({ Pred, BB })) {
-        // 2 live preds.
-        if (OnlyPred)
+      if (LiveEdges.count({ Pred, BB })) {
+        Value *Incoming = PN.getIncomingValueForBlock(Pred);
+        // Two inputs.
+        if (OnlyInput && OnlyInput != Incoming)
           return nullptr;
-        OnlyPred = Pred;
+        OnlyInput = Incoming;
       }
 
-    assert(OnlyPred && "No live predecessors?");
-    return OnlyPred;
+    assert(OnlyInput && "No live predecessors?");
+    return OnlyInput;
   };
   DenseMap<Value *, const SCEV *> FirstIterSCEV;
 
@@ -289,17 +291,16 @@
     }
 
     // If this block has only one live pred, map its phis onto their SCEVs.
-    if (auto *OnlyPred = GetSolePredecessorOnFirstIteration(BB))
-      for (auto &PN : BB->phis()) {
-        if (!SE.isSCEVable(PN.getType()))
-          continue;
-        auto *Incoming = PN.getIncomingValueForBlock(OnlyPred);
-        if (DT.dominates(Incoming, BB->getTerminator())) {
-          const SCEV *IncSCEV =
-              getSCEVOnFirstIteration(Incoming, L, SE, FirstIterSCEV);
-          FirstIterSCEV[&PN] = IncSCEV;
-        }
+    for (auto &PN : BB->phis()) {
+      if (!SE.isSCEVable(PN.getType()))
+        continue;
+      auto *Incoming = GetSoleInputOnFirstIteration(PN);
+      if (Incoming && DT.dominates(Incoming, BB->getTerminator())) {
+        const SCEV *IncSCEV =
+            getSCEVOnFirstIteration(Incoming, L, SE, FirstIterSCEV);
+        FirstIterSCEV[&PN] = IncSCEV;
       }
+    }
 
     using namespace PatternMatch;
     ICmpInst::Predicate Pred;
Index: llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
+++ llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
@@ -667,14 +667,14 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[SUB:%.*]] = sub i32 4, [[SUM]]
 ; CHECK-NEXT:    [[IS_POSITIVE:%.*]] = icmp sgt i32 [[SUB]], 0
 ; CHECK-NEXT:    br i1 [[IS_POSITIVE]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
 ; CHECK:       if.true:
 ; CHECK-NEXT:    br i1 undef, label [[IF_TRUE_1:%.*]], label [[IF_TRUE_2:%.*]]
 ; CHECK:       if.true.1:
-; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK-NEXT:    br label [[BACKEDGE:%.*]]
 ; CHECK:       if.true.2:
 ; CHECK-NEXT:    br label [[BACKEDGE]]
 ; CHECK:       if.false:
@@ -685,9 +685,11 @@
 ; CHECK-NEXT:    br label [[BACKEDGE]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    [[MERGE_PHI:%.*]] = phi i32 [ 0, [[IF_FALSE_1]] ], [ 0, [[IF_FALSE_2]] ], [ [[SUB]], [[IF_TRUE_1]] ], [ [[SUB]], [[IF_TRUE_2]] ]
-; CHECK-NEXT:    [[SUM_NEXT]] = add i32 [[SUM]], [[MERGE_PHI]]
+; CHECK-NEXT:    [[SUM_NEXT:%.*]] = add i32 [[SUM]], [[MERGE_PHI]]
 ; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ne i32 [[SUM_NEXT]], 4
-; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[BACKEDGE_LOOP_CRIT_EDGE:%.*]], label [[DONE:%.*]]
+; CHECK:       backedge.loop_crit_edge:
+; CHECK-NEXT:    unreachable
 ; CHECK:       done:
 ; CHECK-NEXT:    [[SUM_NEXT_LCSSA:%.*]] = phi i32 [ [[SUM_NEXT]], [[BACKEDGE]] ]
 ; CHECK-NEXT:    ret i32 [[SUM_NEXT_LCSSA]]