Revert "Update for LLVM API change in r221024"

This reverts commit r221073 to match upstream revert in r221711.

llvm-svn: 221749
diff --git a/lldb/source/Expression/IRForTarget.cpp b/lldb/source/Expression/IRForTarget.cpp
index 5a2f6e8..bb2b6a3 100644
--- a/lldb/source/Expression/IRForTarget.cpp
+++ b/lldb/source/Expression/IRForTarget.cpp
@@ -1209,7 +1209,7 @@
 
     AllocaInst *alloc = dyn_cast<AllocaInst>(persistent_alloc);
 
-    MDNode *alloc_md = alloc->getMDNode("clang.decl.ptr");
+    MDNode *alloc_md = alloc->getMetadata("clang.decl.ptr");
 
     if (!alloc_md || !alloc_md->getNumOperands())
         return false;