[ThinLTO] Support cloning of temporary DILocation metadata

This is needed to support linking of module-level metadata as a
postpass after function importing, where we will be leaving temporary
metadata on imported instructions until the postpass metadata import.

Also added unittest. Split from D14838.

llvm-svn: 254914
diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
index da4271a..8f346f5 100644
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -813,6 +813,14 @@
   EXPECT_FALSE(L->isResolved());
 }
 
+TEST_F(DILocationTest, cloneTemporary) {
+  MDNode *N = MDNode::get(Context, None);
+  auto L = DILocation::getTemporary(Context, 2, 7, N);
+  EXPECT_TRUE(L->isTemporary());
+  auto L2 = L->clone();
+  EXPECT_TRUE(L2->isTemporary());
+}
+
 typedef MetadataTest GenericDINodeTest;
 
 TEST_F(GenericDINodeTest, get) {