diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -122,13 +122,9 @@
 Value *PHINode::removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty) {
   Value *Removed = getIncomingValue(Idx);
 
-  // Move everything after this operand down.
-  //
-  // FIXME: we could just swap with the end of the list, then erase.  However,
-  // clients might not expect this to happen.  The code as it is thrashes the
-  // use/def lists, which is kinda lame.
-  std::copy(op_begin() + Idx + 1, op_end(), op_begin() + Idx);
-  std::copy(block_begin() + Idx + 1, block_end(), block_begin() + Idx);
+  // Swap ops to remove with last op.
+  *(op_begin() + Idx)->swap(*std::prev(op_end()));
+  std::iter_swap(block_begin() + Idx, std::prev(block_end()));
 
   // Nuke the last value.
   Op<-1>().set(nullptr);