Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186274 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index 7ca2bee..c52e675 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1539,7 +1539,7 @@
       // transformations that may either eliminate the tied operands or
       // improve the opportunities for coalescing away the register copy.
       if (TiedOperands.size() == 1) {
-        SmallVector<std::pair<unsigned, unsigned>, 4> &TiedPairs
+        SmallVectorImpl<std::pair<unsigned, unsigned> > &TiedPairs
           = TiedOperands.begin()->second;
         if (TiedPairs.size() == 1) {
           unsigned SrcIdx = TiedPairs[0].first;