Index: llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
===================================================================
--- llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -544,21 +544,32 @@
   TBAAStructTagNode TagA(A), TagB(B);
   const MDNode *CommonType = getLeastCommonType(TagA.getAccessType(),
                                                 TagB.getAccessType());
-  if (GenericTag)
-    *GenericTag = createAccessTag(CommonType);
 
   // TODO: We need to check if AccessType of TagA encloses AccessType of
   // TagB to support aggregate AccessType. If yes, return true.
 
   // Climb the type DAG from base type of A to see if we reach base type of B.
   uint64_t OffsetA;
-  if (findAccessType(TagA, TagB.getBaseType(), OffsetA))
-    return OffsetA == TagB.getOffset();
+  if (findAccessType(TagA, TagB.getBaseType(), OffsetA)) {
+    bool SameMemberAccess = OffsetA == TagB.getOffset();
+    if (GenericTag)
+      *GenericTag = SameMemberAccess ? TagB.getNode() :
+                                       createAccessTag(CommonType);
+    return SameMemberAccess;
+  }
 
   // Climb the type DAG from base type of B to see if we reach base type of A.
   uint64_t OffsetB;
-  if (findAccessType(TagB, TagA.getBaseType(), OffsetB))
-    return OffsetB == TagA.getOffset();
+  if (findAccessType(TagB, TagA.getBaseType(), OffsetB)) {
+    bool SameMemberAccess = OffsetB == TagA.getOffset();
+    if (GenericTag)
+      *GenericTag = SameMemberAccess ? TagA.getNode() :
+                                       createAccessTag(CommonType);
+    return SameMemberAccess;
+  }
+
+  if (GenericTag)
+    *GenericTag = createAccessTag(CommonType);
 
   // If the final access types have different roots, they're part of different
   // potentially unrelated type systems, so we must be conservative.
Index: llvm/trunk/test/Transforms/GVN/tbaa.ll
===================================================================
--- llvm/trunk/test/Transforms/GVN/tbaa.ll
+++ llvm/trunk/test/Transforms/GVN/tbaa.ll
@@ -1,7 +1,7 @@
 ; RUN: opt -tbaa -basicaa -gvn -S < %s | FileCheck %s
 
 define i32 @test1(i8* %p, i8* %q) {
-; CHECK: @test1(i8* %p, i8* %q)
+; CHECK-LABEL: @test1(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p)
 ; CHECK-NOT: tbaa
 ; CHECK: %c = add i32 %a, %a
@@ -12,7 +12,7 @@
 }
 
 define i32 @test2(i8* %p, i8* %q) {
-; CHECK: @test2(i8* %p, i8* %q)
+; CHECK-LABEL: @test2(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGC:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
@@ -22,7 +22,7 @@
 }
 
 define i32 @test3(i8* %p, i8* %q) {
-; CHECK: @test3(i8* %p, i8* %q)
+; CHECK-LABEL: @test3(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGB:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !3
@@ -32,7 +32,7 @@
 }
 
 define i32 @test4(i8* %p, i8* %q) {
-; CHECK: @test4(i8* %p, i8* %q)
+; CHECK-LABEL: @test4(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !1
@@ -42,8 +42,8 @@
 }
 
 define i32 @test5(i8* %p, i8* %q) {
-; CHECK: @test5(i8* %p, i8* %q)
-; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
+; CHECK-LABEL: @test5(i8* %p, i8* %q)
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
   %b = call i32 @foo(i8* %p), !tbaa !1
@@ -52,8 +52,8 @@
 }
 
 define i32 @test6(i8* %p, i8* %q) {
-; CHECK: @test6(i8* %p, i8* %q)
-; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
+; CHECK-LABEL: @test6(i8* %p, i8* %q)
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
   %b = call i32 @foo(i8* %p), !tbaa !3
@@ -62,7 +62,7 @@
 }
 
 define i32 @test7(i8* %p, i8* %q) {
-; CHECK: @test7(i8* %p, i8* %q)
+; CHECK-LABEL: @test7(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p)
 ; CHECK-NOT: tbaa
 ; CHECK: %c = add i32 %a, %a
@@ -72,10 +72,8 @@
   ret i32 %c
 }
 
-
-
 define i32 @test8(i32* %p, i32* %q) {
-; CHECK-LABEL: test8
+; CHECK-LABEL: @test8
 ; CHECK-NEXT: store i32 15, i32* %p
 ; CHECK-NEXT: ret i32 0
 ; Since we know the location is invariant, we can forward the
@@ -87,8 +85,9 @@
   %c = sub i32 %a, %b
   ret i32 %c
 }
+
 define i32 @test9(i32* %p, i32* %q) {
-; CHECK-LABEL: test9
+; CHECK-LABEL: @test9
 ; CHECK-NEXT: call void @clobber()
 ; CHECK-NEXT: ret i32 0
 ; Since we know the location is invariant, we can forward the
@@ -101,16 +100,27 @@
   ret i32 %c
 }
 
+define i32 @test10(i8* %p, i8* %q) {
+; If one access encloses the other, then the merged access is the enclosed one
+; and not just the common final access type.
+; CHECK-LABEL: @test10
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAG_X_i:!.*]]
+; CHECK: %c = add i32 %a, %a
+  %a = call i32 @foo(i8* %p), !tbaa !15  ; TAG_X_i
+  %b = call i32 @foo(i8* %p), !tbaa !19  ; TAG_Y_x_i
+  %c = add i32 %a, %b
+  ret i32 %c
+}
 
 declare void @clobber()
 declare i32 @foo(i8*) readonly
 
-; CHECK: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
-; CHECK: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
-; CHECK: [[TYPEA]] = !{!"A", !{{.*}}}
-; CHECK: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
-; CHECK: [[TYPEB]] = !{!"B", [[TYPEA]]}
-; CHECK: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
+; CHECK-DAG: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
+; CHECK-DAG: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
+; CHECK-DAG: [[TYPEA]] = !{!"A", !{{.*}}}
+; CHECK-DAG: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
+; CHECK-DAG: [[TYPEB]] = !{!"B", [[TYPEA]]}
+; CHECK-DAG: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
 !0 = !{!5, !5, i64 0}
 !1 = !{!6, !6, i64 0}
 !2 = !{!"tbaa root"}
@@ -122,8 +132,17 @@
 !8 = !{!"another root"}
 !11 = !{!"scalar type", !8}
 
+; CHECK-DAG: [[TAG_X_i]] = !{[[TYPE_X:!.*]], [[TYPE_int:!.*]], i64 0}
+; CHECK-DAG: [[TYPE_X:!.*]] = !{!"struct X", [[TYPE_int]], i64 0}
+; CHECK-DAG: [[TYPE_int]] = !{!"int", {{!.*}}, i64 0}
+!15 = !{!16, !17, i64 0}            ; TAG_X_i
+!16 = !{!"struct X", !17, i64 0}    ; struct X { int i; };
+!17 = !{!"int", !18, i64 0}
+!18 = !{!"char", !2, i64 0}
 
-;; A TBAA structure who's only point is to have a constant location
+!19 = !{!20, !17, i64 0}            ; TAG_Y_x_i
+!20 = !{!"struct Y", !16, i64 0}    ; struct Y { struct X x; };
+
+; A TBAA structure who's only point is to have a constant location.
 !9 = !{!"yet another root"}
 !10 = !{!"node", !9, i64 1}
-
Index: llvm/trunk/test/Transforms/NewGVN/tbaa.ll
===================================================================
--- llvm/trunk/test/Transforms/NewGVN/tbaa.ll
+++ llvm/trunk/test/Transforms/NewGVN/tbaa.ll
@@ -1,7 +1,7 @@
 ; RUN: opt -tbaa -basicaa -newgvn -S < %s | FileCheck %s
 
 define i32 @test1(i8* %p, i8* %q) {
-; CHECK: @test1(i8* %p, i8* %q)
+; CHECK-LABEL: @test1(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p)
 ; CHECK-NOT: tbaa
 ; CHECK: %c = add i32 %a, %a
@@ -12,7 +12,7 @@
 }
 
 define i32 @test2(i8* %p, i8* %q) {
-; CHECK: @test2(i8* %p, i8* %q)
+; CHECK-LABEL: @test2(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGC:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
@@ -22,7 +22,7 @@
 }
 
 define i32 @test3(i8* %p, i8* %q) {
-; CHECK: @test3(i8* %p, i8* %q)
+; CHECK-LABEL: @test3(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGB:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !3
@@ -32,7 +32,7 @@
 }
 
 define i32 @test4(i8* %p, i8* %q) {
-; CHECK: @test4(i8* %p, i8* %q)
+; CHECK-LABEL: @test4(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !1
@@ -42,8 +42,8 @@
 }
 
 define i32 @test5(i8* %p, i8* %q) {
-; CHECK: @test5(i8* %p, i8* %q)
-; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
+; CHECK-LABEL: @test5(i8* %p, i8* %q)
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
   %b = call i32 @foo(i8* %p), !tbaa !1
@@ -52,8 +52,8 @@
 }
 
 define i32 @test6(i8* %p, i8* %q) {
-; CHECK: @test6(i8* %p, i8* %q)
-; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
+; CHECK-LABEL: @test6(i8* %p, i8* %q)
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
 ; CHECK: %c = add i32 %a, %a
   %a = call i32 @foo(i8* %p), !tbaa !0
   %b = call i32 @foo(i8* %p), !tbaa !3
@@ -62,7 +62,7 @@
 }
 
 define i32 @test7(i8* %p, i8* %q) {
-; CHECK: @test7(i8* %p, i8* %q)
+; CHECK-LABEL: @test7(i8* %p, i8* %q)
 ; CHECK: call i32 @foo(i8* %p)
 ; CHECK-NOT: tbaa
 ; CHECK: %c = add i32 %a, %a
@@ -72,10 +72,8 @@
   ret i32 %c
 }
 
-
-
 define i32 @test8(i32* %p, i32* %q) {
-; CHECK-LABEL: test8
+; CHECK-LABEL: @test8
 ; CHECK-NEXT: store i32 15, i32* %p
 ; CHECK-NEXT: ret i32 0
 ; Since we know the location is invariant, we can forward the
@@ -87,8 +85,9 @@
   %c = sub i32 %a, %b
   ret i32 %c
 }
+
 define i32 @test9(i32* %p, i32* %q) {
-; CHECK-LABEL: test9
+; CHECK-LABEL: @test9
 ; CHECK-NEXT: call void @clobber()
 ; CHECK-NEXT: ret i32 0
 ; Since we know the location is invariant, we can forward the
@@ -101,16 +100,27 @@
   ret i32 %c
 }
 
+define i32 @test10(i8* %p, i8* %q) {
+; If one access encloses the other, then the merged access is the enclosed one
+; and not just the common final access type.
+; CHECK-LABEL: @test10
+; CHECK: call i32 @foo(i8* %p), !tbaa [[TAG_X_i:!.*]]
+; CHECK: %c = add i32 %a, %a
+  %a = call i32 @foo(i8* %p), !tbaa !15  ; TAG_X_i
+  %b = call i32 @foo(i8* %p), !tbaa !19  ; TAG_Y_x_i
+  %c = add i32 %a, %b
+  ret i32 %c
+}
 
 declare void @clobber()
 declare i32 @foo(i8*) readonly
 
-; CHECK: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
-; CHECK: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
-; CHECK: [[TYPEA]] = !{!"A", !{{.*}}}
-; CHECK: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
-; CHECK: [[TYPEB]] = !{!"B", [[TYPEA]]}
-; CHECK: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
+; CHECK-DAG: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
+; CHECK-DAG: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
+; CHECK-DAG: [[TYPEA]] = !{!"A", !{{.*}}}
+; CHECK-DAG: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
+; CHECK-DAG: [[TYPEB]] = !{!"B", [[TYPEA]]}
+; CHECK-DAG: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
 !0 = !{!5, !5, i64 0}
 !1 = !{!6, !6, i64 0}
 !2 = !{!"tbaa root"}
@@ -122,8 +132,17 @@
 !8 = !{!"another root"}
 !11 = !{!"scalar type", !8}
 
+; CHECK-DAG: [[TAG_X_i]] = !{[[TYPE_X:!.*]], [[TYPE_int:!.*]], i64 0}
+; CHECK-DAG: [[TYPE_X:!.*]] = !{!"struct X", [[TYPE_int]], i64 0}
+; CHECK-DAG: [[TYPE_int]] = !{!"int", {{!.*}}, i64 0}
+!15 = !{!16, !17, i64 0}            ; TAG_X_i
+!16 = !{!"struct X", !17, i64 0}    ; struct X { int i; };
+!17 = !{!"int", !18, i64 0}
+!18 = !{!"char", !2, i64 0}
 
-;; A TBAA structure who's only point is to have a constant location
+!19 = !{!20, !17, i64 0}            ; TAG_Y_x_i
+!20 = !{!"struct Y", !16, i64 0}    ; struct Y { struct X x; };
+
+; A TBAA structure who's only point is to have a constant location.
 !9 = !{!"yet another root"}
 !10 = !{!"node", !9, i64 1}
-