Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -476,8 +476,7 @@
 static Instruction::BinaryOps
 getBinOpsForFactorization(Instruction::BinaryOps TopLevelOpcode,
                           BinaryOperator *Op, Value *&LHS, Value *&RHS) {
-  if (!Op)
-    return Instruction::BinaryOpsEnd;
+  assert(Op && "Expected a binary operator");
 
   LHS = Op->getOperand(0);
   RHS = Op->getOperand(1);
@@ -507,11 +506,7 @@
                                const DataLayout &DL, BinaryOperator &I,
                                Instruction::BinaryOps InnerOpcode, Value *A,
                                Value *B, Value *C, Value *D) {
-
-  // If any of A, B, C, D are null, we can not factor I, return early.
-  // Checking A and C should be enough.
-  if (!A || !C || !B || !D)
-    return nullptr;
+  assert(A && B && C && D && "All values must be provided");
 
   Value *V = nullptr;
   Value *SimplifiedInst = nullptr;
@@ -605,31 +600,39 @@
   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
   BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
   BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
+  Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
 
-  // Factorization.
-  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
-  auto TopLevelOpcode = I.getOpcode();
-  auto LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B);
-  auto RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D);
-
-  // The instruction has the form "(A op' B) op (C op' D)".  Try to factorize
-  // a common term.
-  if (LHSOpcode == RHSOpcode) {
-    if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, C, D))
-      return V;
-  }
+  {
+    // Factorization.
+    Value *A, *B, *C, *D;
+    Instruction::BinaryOps LHSOpcode, RHSOpcode;
+    if (Op0)
+      LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B);
+    if (Op1)
+      RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D);
+
+    // The instruction has the form "(A op' B) op (C op' D)".  Try to factorize
+    // a common term.
+    if (Op0 && Op1 && LHSOpcode == RHSOpcode)
+      if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, C, D))
+        return V;
+
+    // The instruction has the form "(A op' B) op (C)".  Try to factorize common
+    // term.
+    if (Op0)
+      if (Value *Ident = getIdentityValue(LHSOpcode, RHS))
+        if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, RHS,
+                                        Ident))
+          return V;
 
-  // The instruction has the form "(A op' B) op (C)".  Try to factorize common
-  // term.
-  if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, RHS,
-                                  getIdentityValue(LHSOpcode, RHS)))
-    return V;
-
-  // The instruction has the form "(B) op (C op' D)".  Try to factorize common
-  // term.
-  if (Value *V = tryFactorization(Builder, DL, I, RHSOpcode, LHS,
-                                  getIdentityValue(RHSOpcode, LHS), C, D))
-    return V;
+    // The instruction has the form "(B) op (C op' D)".  Try to factorize common
+    // term.
+    if (Op1)
+      if (Value *Ident = getIdentityValue(RHSOpcode, LHS))
+        if (Value *V = tryFactorization(Builder, DL, I, RHSOpcode, LHS, Ident,
+                                        C, D))
+          return V;
+  }
 
   // Expansion.
   if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) {