Replace some unnecessary vector copies with references.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190770 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 596b7a3..104eacd 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -502,7 +502,7 @@
 
   // Walk the entire region, count number of defs for each register, and
   // collect potential LICM candidates.
-  const std::vector<MachineBasicBlock*> Blocks = CurLoop->getBlocks();
+  const std::vector<MachineBasicBlock *> &Blocks = CurLoop->getBlocks();
   for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
     MachineBasicBlock *BB = Blocks[i];
 
@@ -584,7 +584,7 @@
 /// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the current
 /// loop, and make sure it is not killed by any instructions in the loop.
 void MachineLICM::AddToLiveIns(unsigned Reg) {
-  const std::vector<MachineBasicBlock*> Blocks = CurLoop->getBlocks();
+  const std::vector<MachineBasicBlock *> &Blocks = CurLoop->getBlocks();
   for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
     MachineBasicBlock *BB = Blocks[i];
     if (!BB->isLiveIn(Reg))