diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index 010f17aae0b..6ef0c97d375 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -910,14 +910,14 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
     // A*A*B + A*A*C   -->   A*(A*B+A*C)   -->   A*(A*(B+C))
     assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
     (void)NumAddedValues;
-    V = ReassociateExpression(cast<BinaryOperator>(V));
+    RedoInsts.push_back(V);
 
     // Create the multiply.
     Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
 
     // Rerun associate on the multiply in case the inner expression turned into
     // a multiply.  We want to make sure that we keep things in canonical form.
-    V2 = ReassociateExpression(cast<BinaryOperator>(V2));
+    RedoInsts.push_back(V2);
 
     // If every add operand included the factor (e.g. "A*B + A*C"), then the
     // entire result expression is just the multiply "A*(B+C)".
@@ -1070,9 +1070,8 @@ Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
 
     // Reset the base value of the first factor to the new expression tree.
     // We'll remove all the factors with the same power in a second pass.
-    Factors[LastIdx].Base
-      = ReassociateExpression(
-          cast<BinaryOperator>(buildMultiplyTree(Builder, InnerProduct)));
+    Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
+    RedoInsts.push_back(Factors[LastIdx].Base);
 
     LastIdx = Idx;
   }
@@ -1098,8 +1097,9 @@ Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
   if (OuterProduct.size() == 1)
     return OuterProduct.front();
 
-  return ReassociateExpression(
-    cast<BinaryOperator>(buildMultiplyTree(Builder, OuterProduct)));
+  Value *V = buildMultiplyTree(Builder, OuterProduct);
+  RedoInsts.push_back(V);
+  return V;
 }
 
 Value *Reassociate::OptimizeMul(BinaryOperator *I,
diff --git a/test/Transforms/Reassociate/2012-05-08-UndefLeak.ll b/test/Transforms/Reassociate/2012-05-08-UndefLeak.ll
new file mode 100644
index 00000000000..80193615693
--- /dev/null
+++ b/test/Transforms/Reassociate/2012-05-08-UndefLeak.ll
@@ -0,0 +1,79 @@
+; RUN: opt < %s -reassociate -S | FileCheck %s
+; PR12169
+
+define i64 @f(i64 %x0) {
+; CHECK-NOT: undef
+  %t0 = add i64 %x0, 1
+  %t1 = add i64 %x0, 2
+  %t2 = add i64 %x0, 3
+  %t3 = add i64 %x0, 4
+  %t4 = add i64 %x0, 5
+  %t5 = add i64 %x0, 6
+  %t6 = add i64 %x0, 7
+  %t7 = add i64 %x0, 8
+  %t8 = add i64 %x0, 9
+  %t9 = add i64 %x0, 10
+  %t10 = add i64 %x0, 11
+  %t11 = add i64 %x0, 12
+  %t12 = add i64 %x0, 13
+  %t13 = add i64 %x0, 14
+  %t14 = add i64 %x0, 15
+  %t15 = add i64 %x0, 16
+  %t16 = add i64 %x0, 17
+  %t17 = add i64 %x0, 18
+  %t18 = add i64 %t17, %t0
+  %t19 = add i64 %t18, %t1
+  %t20 = add i64 %t19, %t2
+  %t21 = add i64 %t20, %t3
+  %t22 = add i64 %t21, %t4
+  %t23 = add i64 %t22, %t5
+  %t24 = add i64 %t23, %t6
+  %t25 = add i64 %t24, %t7
+  %t26 = add i64 %t25, %t8
+  %t27 = add i64 %t26, %t9
+  %t28 = add i64 %t27, %t10
+  %t29 = add i64 %t28, %t11
+  %t30 = add i64 %t29, %t12
+  %t31 = add i64 %t30, %t13
+  %t32 = add i64 %t31, %t14
+  %t33 = add i64 %t32, %t15
+  %t34 = add i64 %t33, %t16
+  %t35 = add i64 %t34, %x0
+  %t36 = add i64 %t0, %t1
+  %t37 = add i64 %t36, %t2
+  %t38 = add i64 %t37, %t3
+  %t39 = add i64 %t38, %t4
+  %t40 = add i64 %t39, %t5
+  %t41 = add i64 %t40, %t6
+  %t42 = add i64 %t41, %t7
+  %t43 = add i64 %t42, %t8
+  %t44 = add i64 %t43, %t9
+  %t45 = add i64 %t44, %t10
+  %t46 = add i64 %t45, %t11
+  %t47 = add i64 %t46, %t12
+  %t48 = add i64 %t47, %t13
+  %t49 = add i64 %t48, %t14
+  %t50 = add i64 %t49, %t15
+  %t51 = add i64 %t50, %t16
+  %t52 = add i64 %t51, %t17
+  %t53 = add i64 %t52, %t18
+  %t54 = add i64 %t53, %t19
+  %t55 = add i64 %t54, %t20
+  %t56 = add i64 %t55, %t21
+  %t57 = add i64 %t56, %t22
+  %t58 = add i64 %t57, %t23
+  %t59 = add i64 %t58, %t24
+  %t60 = add i64 %t59, %t25
+  %t61 = add i64 %t60, %t26
+  %t62 = add i64 %t61, %t27
+  %t63 = add i64 %t62, %t28
+  %t64 = add i64 %t63, %t29
+  %t65 = add i64 %t64, %t30
+  %t66 = add i64 %t65, %t31
+  %t67 = add i64 %t66, %t32
+  %t68 = add i64 %t67, %t33
+  %t69 = add i64 %t68, %t34
+  %t70 = add i64 %t69, %t35
+  %t71 = add i64 %t70, %x0
+  ret i64 %t71
+}
diff --git a/test/Transforms/Reassociate/multistep.ll b/test/Transforms/Reassociate/multistep.ll
new file mode 100644
index 00000000000..7466d2e99d8
--- /dev/null
+++ b/test/Transforms/Reassociate/multistep.ll
@@ -0,0 +1,31 @@
+; RUN: opt < %s -reassociate -S | FileCheck %s
+
+define i64 @multistep1(i64 %a, i64 %b, i64 %c) {
+; Check that a*a*b+a*a*c is turned into a*(a*(b+c)).
+; CHECK: @multistep1
+  %t0 = mul i64 %a, %b
+  %t1 = mul i64 %a, %t0 ; a*(a*b)
+  %t2 = mul i64 %a, %c
+  %t3 = mul i64 %a, %t2 ; a*(a*c)
+  %t4 = add i64 %t1, %t3
+; CHECK-NEXT: add i64 %c, %b
+; CHECK-NEXT: mul i64 %tmp{{.*}}, %a
+; CHECK-NEXT: mul i64 %tmp{{.*}}, %a
+; CHECK-NEXT: ret
+  ret i64 %t4
+}
+
+define i64 @multistep2(i64 %a, i64 %b, i64 %c, i64 %d) {
+; Check that a*b+a*c+d is turned into a*(b+c)+d.
+; CHECK: @multistep2
+  %t0 = mul i64 %a, %b
+  %t1 = mul i64 %a, %c
+  %t2 = add i64 %t1, %d ; a*c+d
+  %t3 = add i64 %t0, %t2 ; a*b+(a*c+d)
+; CHECK-NEXT: add i64 %c, %b
+; CHECK-NEXT: mul i64 %tmp{{.*}}, %a
+; CHECK-NEXT: add i64 %tmp{{.*}}, %d
+; CHECK-NEXT: ret
+  ret i64 %t3
+}
+