Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -2189,19 +2189,20 @@
 
 VarDecl *VarDecl::getActingDefinition() {
   DefinitionKind Kind = isThisDeclarationADefinition();
-  if (Kind != TentativeDefinition)
+  if (Kind != TentativeDefinition || hasDefinition())
     return nullptr;
 
-  VarDecl *LastTentative = nullptr;
-  VarDecl *First = getFirstDecl();
-  for (auto I : First->redecls()) {
-    Kind = I->isThisDeclarationADefinition();
-    if (Kind == Definition)
-      return nullptr;
+  // Loop through the declaration chain, starting with the most recent.
+  for (VarDecl *Decl = getMostRecentDecl(); Decl;
+       Decl = Decl->getPreviousDecl()) {
+    Kind = Decl->isThisDeclarationADefinition();
+
+    // Return the first TentativeDefinition that is encountered.
     if (Kind == TentativeDefinition)
-      LastTentative = I;
+      return Decl;
   }
-  return LastTentative;
+
+  return nullptr;
 }
 
 VarDecl *VarDecl::getDefinition(ASTContext &C) {
Index: clang/test/CodeGen/attr-tentative-definition.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-tentative-definition.c
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -emit-llvm < %s | FileCheck %s
+
+char arr[10];
+char arr[10] __attribute__((section("datadata")));
+char arr[10] __attribute__((aligned(16)));
+
+// CHECK: @arr = dso_local global [10 x i8] zeroinitializer, section "datadata", align 16