Index: lib/Transforms/Scalar/Reassociate.cpp
===================================================================
--- lib/Transforms/Scalar/Reassociate.cpp
+++ lib/Transforms/Scalar/Reassociate.cpp
@@ -2264,7 +2264,7 @@
   MadeChange = false;
   for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
     // Optimize every instruction in the basic block.
-    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; )
+    for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; ) {
       if (isInstructionTriviallyDead(II)) {
         EraseInst(II++);
       } else {
@@ -2273,13 +2273,17 @@
         ++II;
       }
 
-    // If this produced extra instructions to optimize, handle them now.
-    while (!RedoInsts.empty()) {
-      Instruction *I = RedoInsts.pop_back_val();
-      if (isInstructionTriviallyDead(I))
-        EraseInst(I);
-      else
-        OptimizeInst(I);
+      // If this produced extra instructions to optimize, handle them now.
+      while (!RedoInsts.empty()) {
+        Instruction *I = RedoInsts.pop_back_val();
+        if (I == II)
+          // Will be processed next iteration on the basic block
+          continue;
+        if (isInstructionTriviallyDead(I))
+          EraseInst(I);
+        else
+          OptimizeInst(I);
+      }
     }
   }
 
Index: test/Transforms/Reassociate/crash3.ll
===================================================================
--- /dev/null
+++ test/Transforms/Reassociate/crash3.ll
@@ -0,0 +1,15 @@
+; RUN: opt -reassociate -o - -S %s | FileCheck %s
+
+declare void @bar(i32)
+
+define i32 @foo(i32 %in) {
+; CHECK-LABEL: @foo
+; CHECK: %_factor = mul i32 %_3, -4
+  %_0 = add i32 %in, 1
+  %_1 = mul i32 %in, -2
+  %_2 = add i32 %_0, %_1
+  %_3 = add i32 %_1, %_2
+  %_4 = add i32 %_3, 1
+  %_5 = add i32 %in, %_3
+  ret i32 %_5
+}