Index: cfe/trunk/lib/AST/ASTImporter.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp
+++ cfe/trunk/lib/AST/ASTImporter.cpp
@@ -1923,9 +1923,8 @@
       }
       
       if (RecordDecl *FoundRecord = dyn_cast<RecordDecl>(Found)) {
-        if (D->isAnonymousStructOrUnion() && 
-            FoundRecord->isAnonymousStructOrUnion()) {
-          // If both anonymous structs/unions are in a record context, make sure
+        if (!SearchName) {
+          // If both unnamed structs/unions are in a record context, make sure
           // they occur in the same location in the context records.
           if (Optional<unsigned> Index1 =
                   StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(
Index: cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
+++ cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
@@ -1256,6 +1256,10 @@
     // If the field looks like this:
     // struct { ... } A;
     QualType FieldType = F->getType();
+    // In case of nested structs.
+    while (const auto *ElabType = dyn_cast<ElaboratedType>(FieldType))
+      FieldType = ElabType->getNamedType();
+
     if (const auto *RecType = dyn_cast<RecordType>(FieldType)) {
       const RecordDecl *RecDecl = RecType->getDecl();
       if (RecDecl->getDeclContext() == Owner && !RecDecl->getIdentifier()) {
Index: cfe/trunk/test/ASTMerge/struct/Inputs/struct1.c
===================================================================
--- cfe/trunk/test/ASTMerge/struct/Inputs/struct1.c
+++ cfe/trunk/test/ASTMerge/struct/Inputs/struct1.c
@@ -77,3 +77,65 @@
 } S13;
 
 S13 x13;
+
+// Matches
+struct Unnamed {
+  union {
+    struct {
+      int i;
+    } S;
+    struct {
+      float i;
+    } R;
+  } U;
+} x14;
+
+// Matches
+struct DeepUnnamed {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x15;
+
+// Mismatch due to unnamed struct used internally
+struct DeepUnnamedError {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i; // Mismatch here.
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x16;
Index: cfe/trunk/test/ASTMerge/struct/Inputs/struct2.c
===================================================================
--- cfe/trunk/test/ASTMerge/struct/Inputs/struct2.c
+++ cfe/trunk/test/ASTMerge/struct/Inputs/struct2.c
@@ -74,3 +74,65 @@
 } S13;
 
 S13 x13;
+
+// Matches
+struct Unnamed {
+  union {
+    struct {
+      int i;
+    } S;
+    struct {
+      float i;
+    } R;
+  } U;
+} x14;
+
+// Matches
+struct DeepUnnamed {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x15;
+
+// Mismatch due to unnamed struct used internally
+struct DeepUnnamedError {
+  union {
+    union {
+      struct {
+        long i;
+      } S;
+      struct {
+        int i;
+      } R;
+    } U1;
+    union {
+      struct {
+        float i; // Mismatch here.
+      } S;
+      struct {
+        float i;
+      } T;
+    } U2;
+  } U;
+  struct {
+    long i;
+  } V;
+} x16;
Index: cfe/trunk/test/ASTMerge/struct/test.c
===================================================================
--- cfe/trunk/test/ASTMerge/struct/test.c
+++ cfe/trunk/test/ASTMerge/struct/test.c
@@ -44,4 +44,12 @@
 // CHECK: struct2.c:72:7: note: field 'i' has type 'int' here
 // CHECK: struct2.c:76:5: error: external variable 'x13' declared with incompatible types in different translation units ('S13' vs. 'S13')
 // CHECK: struct1.c:79:5: note: declared here with type 'S13'
-// CHECK: 9 warnings and 8 errors generated
+// CHECK: struct1.c:130:7: warning: type 'struct DeepUnnamedError::(anonymous at [[PATH_TO_INPUTS:.+]]/struct1.c:130:7)' has incompatible definitions in different translation units
+// CHECK: struct1.c:131:14: note: field 'i' has type 'long' here
+// CHECK: struct2.c:128:15: note: field 'i' has type 'float' here
+// CHECK: struct1.c:129:5: warning: type 'union DeepUnnamedError::(anonymous at [[PATH_TO_INPUTS]]/struct1.c:129:5)' has incompatible definitions in different translation units
+// CHECK: struct1.c:132:9: note: field 'S' has type 'struct (anonymous struct at [[PATH_TO_INPUTS]]/struct1.c:130:7)' here
+// CHECK: struct2.c:129:9: note: field 'S' has type 'struct (anonymous struct at [[PATH_TO_INPUTS]]/struct2.c:127:7)' here
+// CHECK: struct2.c:138:3: error: external variable 'x16' declared with incompatible types in different translation units ('struct DeepUnnamedError' vs. 'struct DeepUnnamedError')
+// CHECK: struct1.c:141:3: note: declared here with type 'struct DeepUnnamedError'
+// CHECK: 11 warnings and 9 errors generated