Aliasing rules for struct-path aware TBAA.

Added PathAliases to check if two struct-path tags can alias.
Added command line option -struct-path-tbaa.

llvm-svn: 179337

diff --git a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 68e43b2..c14c593 100644 (file)
--- a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -71,6 +71,7 @@ using namespace llvm;
 // achieved by stripping the !tbaa tags from IR, but this option is sometimes
 // more convenient.
 static cl::opt<bool> EnableTBAA("enable-tbaa", cl::init(true));
+static cl::opt<bool> EnableStructPathTBAA("struct-path-tbaa", cl::init(false));
 
 namespace {
   /// TBAANode - This is a simple wrapper around an MDNode which provides a
@@ -109,6 +110,76 @@ namespace {
       return CI->getValue()[0];
     }
   };
+
+  /// This is a simple wrapper around an MDNode which provides a
+  /// higher-level interface by hiding the details of how alias analysis
+  /// information is encoded in its operands.
+  class TBAAStructTagNode {
+    /// This node should be created with createTBAAStructTagNode.
+    const MDNode *Node;
+
+  public:
+    TBAAStructTagNode() : Node(0) {}
+    explicit TBAAStructTagNode(const MDNode *N) : Node(N) {}
+
+    /// Get the MDNode for this TBAAStructTagNode.
+    const MDNode *getNode() const { return Node; }
+
+    const MDNode *getBaseType() const {
+      return dyn_cast_or_null<MDNode>(Node->getOperand(0));
+    }
+    const MDNode *getAccessType() const {
+      return dyn_cast_or_null<MDNode>(Node->getOperand(1));
+    }
+    uint64_t getOffset() const {
+      return cast<ConstantInt>(Node->getOperand(2))->getZExtValue();
+    }
+  };
+
+  /// This is a simple wrapper around an MDNode which provides a
+  /// higher-level interface by hiding the details of how alias analysis
+  /// information is encoded in its operands.
+  class TBAAStructTypeNode {
+    /// This node should be created with createTBAAStructTypeNode.
+    const MDNode *Node;
+
+  public:
+    TBAAStructTypeNode() : Node(0) {}
+    explicit TBAAStructTypeNode(const MDNode *N) : Node(N) {}
+
+    /// Get the MDNode for this TBAAStructTypeNode.
+    const MDNode *getNode() const { return Node; }
+
+    /// Get this TBAAStructTypeNode's field in the type DAG with
+    /// given offset. Update the offset to be relative to the field type.
+    TBAAStructTypeNode getParent(uint64_t &Offset) const {
+      if (Node->getNumOperands() < 2)
+        return TBAAStructTypeNode();
+
+      // Assume the offsets are in order. We return the previous field if
+      // the current offset is bigger than the given offset.
+      unsigned TheIdx = 0;
+      for (unsigned Idx = 1; Idx < Node->getNumOperands(); Idx += 2) {
+        uint64_t Cur = cast<ConstantInt>(Node->getOperand(Idx))->getZExtValue();
+        if (Cur > Offset) {
+          assert(Idx >= 3 &&
+                 "TBAAStructTypeNode::getParent should have an offset match!");
+          TheIdx = Idx - 2;
+          break;
+        }
+      }
+      // Move along the last field.
+      if (TheIdx == 0)
+        TheIdx = Node->getNumOperands() - 2;
+      uint64_t Cur = cast<ConstantInt>(Node->getOperand(TheIdx))->
+                       getZExtValue();
+      Offset -= Cur;
+      MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(TheIdx + 1));
+      if (!P)
+        return TBAAStructTypeNode();
+      return TBAAStructTypeNode(P);
+    }
+  };
 }
 
 namespace {
@@ -137,6 +208,7 @@ namespace {
     }
 
     bool Aliases(const MDNode *A, const MDNode *B) const;
+    bool PathAliases(const MDNode *A, const MDNode *B) const;
 
   private:
     virtual void getAnalysisUsage(AnalysisUsage &AU) const;
@@ -171,6 +243,9 @@ TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
 bool
 TypeBasedAliasAnalysis::Aliases(const MDNode *A,
                                 const MDNode *B) const {
+  if (EnableStructPathTBAA)
+    return PathAliases(A, B);
+
   // Keep track of the root node for A and B.
   TBAANode RootA, RootB;
 
@@ -209,6 +284,67 @@ TypeBasedAliasAnalysis::Aliases(const MDNode *A,
   return false;
 }
 
+/// Test whether the struct-path tag represented by A may alias the
+/// struct-path tag represented by B.
+bool
+TypeBasedAliasAnalysis::PathAliases(const MDNode *A,
+                                    const MDNode *B) const {
+  // Keep track of the root node for A and B.
+  TBAAStructTypeNode RootA, RootB;
+  TBAAStructTagNode TagA(A), TagB(B);
+
+  // TODO: We need to check if AccessType of TagA encloses AccessType of
+  // TagB to support aggregate AccessType. If yes, return true.
+
+  // Start from the base type of A, follow the edge with the correct offset in
+  // the type DAG and adjust the offset until we reach the base type of B or
+  // until we reach the Root node.
+  // Compare the adjusted offset once we have the same base.
+
+  // Climb the type DAG from base type of A to see if we reach base type of B.
+  const MDNode *BaseA = TagA.getBaseType();
+  const MDNode *BaseB = TagB.getBaseType();
+  uint64_t OffsetA = TagA.getOffset(), OffsetB = TagB.getOffset();
+  for (TBAAStructTypeNode T(BaseA); ; ) {
+    if (T.getNode() == BaseB)
+      // Base type of A encloses base type of B, check if the offsets match.
+      return OffsetA == OffsetB;
+
+    RootA = T;
+    // Follow the edge with the correct offset, OffsetA will be adjusted to
+    // be relative to the field type.
+    T = T.getParent(OffsetA);
+    if (!T.getNode())
+      break;
+  }
+
+  // Reset OffsetA and climb the type DAG from base type of B to see if we reach
+  // base type of A.
+  OffsetA = TagA.getOffset();
+  for (TBAAStructTypeNode T(BaseB); ; ) {
+    if (T.getNode() == BaseA)
+      // Base type of B encloses base type of A, check if the offsets match.
+      return OffsetA == OffsetB;
+
+    RootB = T;
+    // Follow the edge with the correct offset, OffsetB will be adjusted to
+    // be relative to the field type.
+    T = T.getParent(OffsetB);
+    if (!T.getNode())
+      break;
+  }
+
+  // Neither node is an ancestor of the other.
+
+  // If they have different roots, they're part of different potentially
+  // unrelated type systems, so we must be conservative.
+  if (RootA.getNode() != RootB.getNode())
+    return true;
+
+  // If they have the same root, then we've proved there's no alias.
+  return false;
+}
+
 AliasAnalysis::AliasResult
 TypeBasedAliasAnalysis::alias(const Location &LocA,
                               const Location &LocB) {

diff --git a/llvm/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll b/llvm/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll
new file mode 100644 (file)
index 0000000..c63abca
--- /dev/null
+++ b/llvm/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll
@@ -0,0 +1,392 @@
+; RUN: opt < %s -tbaa -basicaa -struct-path-tbaa -aa-eval -evaluate-tbaa -print-no-aliases -print-may-aliases -disable-output 2>&1 | FileCheck %s
+; RUN: opt < %s -tbaa -basicaa -struct-path-tbaa -gvn -S | FileCheck %s --check-prefix=OPT
+; Generated from clang/test/CodeGen/tbaa.cpp with "-O1 -struct-path-tbaa -disable-llvm-optzns".
+
+%struct.StructA = type { i16, i32, i16, i32 }
+%struct.StructB = type { i16, %struct.StructA, i32 }
+%struct.StructS = type { i16, i32 }
+%struct.StructS2 = type { i16, i32 }
+%struct.StructC = type { i16, %struct.StructB, i32 }
+%struct.StructD = type { i16, %struct.StructB, i32, i8 }
+
+define i32 @_Z1gPjP7StructAy(i32* %s, %struct.StructA* %A, i64 %count) #0 {
+entry:
+; Access to i32* and &(A->f32).
+; CHECK: Function
+; CHECK: MayAlias:   store i32 4, i32* %f32, align 4, !tbaa !8 <->   store i32 1, i32* %0, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; OPT: %[[RET:.*]] = load i32*
+; OPT: ret i32 %[[RET]]
+  %s.addr = alloca i32*, align 8
+  %A.addr = alloca %struct.StructA*, align 8
+  %count.addr = alloca i64, align 8
+  store i32* %s, i32** %s.addr, align 8, !tbaa !0
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load i32** %s.addr, align 8, !tbaa !0
+  store i32 1, i32* %0, align 4, !tbaa !6
+  %1 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %1, i32 0, i32 1
+  store i32 4, i32* %f32, align 4, !tbaa !8
+  %2 = load i32** %s.addr, align 8, !tbaa !0
+  %3 = load i32* %2, align 4, !tbaa !6
+  ret i32 %3
+}
+
+define i32 @_Z2g2PjP7StructAy(i32* %s, %struct.StructA* %A, i64 %count) #0 {
+entry:
+; Access to i32* and &(A->f16).
+; CHECK: Function
+; CHECK: NoAlias:   store i16 4, i16* %f16, align 2, !tbaa !8 <->   store i32 1, i32* %0, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i16 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %s.addr = alloca i32*, align 8
+  %A.addr = alloca %struct.StructA*, align 8
+  %count.addr = alloca i64, align 8
+  store i32* %s, i32** %s.addr, align 8, !tbaa !0
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load i32** %s.addr, align 8, !tbaa !0
+  store i32 1, i32* %0, align 4, !tbaa !6
+  %1 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f16 = getelementptr inbounds %struct.StructA* %1, i32 0, i32 0
+  store i16 4, i16* %f16, align 2, !tbaa !11
+  %2 = load i32** %s.addr, align 8, !tbaa !0
+  %3 = load i32* %2, align 4, !tbaa !6
+  ret i32 %3
+}
+
+define i32 @_Z2g3P7StructAP7StructBy(%struct.StructA* %A, %struct.StructB* %B, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(B->a.f32).
+; CHECK: Function
+; CHECK: MayAlias:   store i32 4, i32* %f321, align 4, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; OPT: %[[RET:.*]] = load i32*
+; OPT: ret i32 %[[RET]]
+  %A.addr = alloca %struct.StructA*, align 8
+  %B.addr = alloca %struct.StructB*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructB* %B, %struct.StructB** %B.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructB** %B.addr, align 8, !tbaa !0
+  %a = getelementptr inbounds %struct.StructB* %1, i32 0, i32 1
+  %f321 = getelementptr inbounds %struct.StructA* %a, i32 0, i32 1
+  store i32 4, i32* %f321, align 4, !tbaa !12
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f322 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f322, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g4P7StructAP7StructBy(%struct.StructA* %A, %struct.StructB* %B, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(B->a.f16).
+; CHECK: Function
+; CHECK: NoAlias:   store i16 4, i16* %f16, align 2, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i16 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %A.addr = alloca %struct.StructA*, align 8
+  %B.addr = alloca %struct.StructB*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructB* %B, %struct.StructB** %B.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructB** %B.addr, align 8, !tbaa !0
+  %a = getelementptr inbounds %struct.StructB* %1, i32 0, i32 1
+  %f16 = getelementptr inbounds %struct.StructA* %a, i32 0, i32 0
+  store i16 4, i16* %f16, align 2, !tbaa !14
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f321, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g5P7StructAP7StructBy(%struct.StructA* %A, %struct.StructB* %B, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(B->f32).
+; CHECK: Function
+; CHECK: NoAlias:   store i32 4, i32* %f321, align 4, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %A.addr = alloca %struct.StructA*, align 8
+  %B.addr = alloca %struct.StructB*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructB* %B, %struct.StructB** %B.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructB** %B.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructB* %1, i32 0, i32 2
+  store i32 4, i32* %f321, align 4, !tbaa !15
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f322 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f322, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g6P7StructAP7StructBy(%struct.StructA* %A, %struct.StructB* %B, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(B->a.f32_2).
+; CHECK: Function
+; CHECK: NoAlias:   store i32 4, i32* %f32_2, align 4, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %A.addr = alloca %struct.StructA*, align 8
+  %B.addr = alloca %struct.StructB*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructB* %B, %struct.StructB** %B.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructB** %B.addr, align 8, !tbaa !0
+  %a = getelementptr inbounds %struct.StructB* %1, i32 0, i32 1
+  %f32_2 = getelementptr inbounds %struct.StructA* %a, i32 0, i32 3
+  store i32 4, i32* %f32_2, align 4, !tbaa !16
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f321, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g7P7StructAP7StructSy(%struct.StructA* %A, %struct.StructS* %S, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(S->f32).
+; CHECK: Function
+; CHECK: NoAlias:   store i32 4, i32* %f321, align 4, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %A.addr = alloca %struct.StructA*, align 8
+  %S.addr = alloca %struct.StructS*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructS* %S, %struct.StructS** %S.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructS* %1, i32 0, i32 1
+  store i32 4, i32* %f321, align 4, !tbaa !17
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f322 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f322, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g8P7StructAP7StructSy(%struct.StructA* %A, %struct.StructS* %S, i64 %count) #0 {
+entry:
+; Access to &(A->f32) and &(S->f16).
+; CHECK: Function
+; CHECK: NoAlias:   store i16 4, i16* %f16, align 2, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i16 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %A.addr = alloca %struct.StructA*, align 8
+  %S.addr = alloca %struct.StructS*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructA* %A, %struct.StructA** %A.addr, align 8, !tbaa !0
+  store %struct.StructS* %S, %struct.StructS** %S.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructA* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !8
+  %1 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f16 = getelementptr inbounds %struct.StructS* %1, i32 0, i32 0
+  store i16 4, i16* %f16, align 2, !tbaa !19
+  %2 = load %struct.StructA** %A.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructA* %2, i32 0, i32 1
+  %3 = load i32* %f321, align 4, !tbaa !8
+  ret i32 %3
+}
+
+define i32 @_Z2g9P7StructSP8StructS2y(%struct.StructS* %S, %struct.StructS2* %S2, i64 %count) #0 {
+entry:
+; Access to &(S->f32) and &(S2->f32).
+; CHECK: Function
+; CHECK: NoAlias:   store i32 4, i32* %f321, align 4, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %S.addr = alloca %struct.StructS*, align 8
+  %S2.addr = alloca %struct.StructS2*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructS* %S, %struct.StructS** %S.addr, align 8, !tbaa !0
+  store %struct.StructS2* %S2, %struct.StructS2** %S2.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructS* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !17
+  %1 = load %struct.StructS2** %S2.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructS2* %1, i32 0, i32 1
+  store i32 4, i32* %f321, align 4, !tbaa !20
+  %2 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f322 = getelementptr inbounds %struct.StructS* %2, i32 0, i32 1
+  %3 = load i32* %f322, align 4, !tbaa !17
+  ret i32 %3
+}
+
+define i32 @_Z3g10P7StructSP8StructS2y(%struct.StructS* %S, %struct.StructS2* %S2, i64 %count) #0 {
+entry:
+; Access to &(S->f32) and &(S2->f16).
+; CHECK: Function
+; CHECK: NoAlias:   store i16 4, i16* %f16, align 2, !tbaa !10 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i16 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %S.addr = alloca %struct.StructS*, align 8
+  %S2.addr = alloca %struct.StructS2*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructS* %S, %struct.StructS** %S.addr, align 8, !tbaa !0
+  store %struct.StructS2* %S2, %struct.StructS2** %S2.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f32 = getelementptr inbounds %struct.StructS* %0, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !17
+  %1 = load %struct.StructS2** %S2.addr, align 8, !tbaa !0
+  %f16 = getelementptr inbounds %struct.StructS2* %1, i32 0, i32 0
+  store i16 4, i16* %f16, align 2, !tbaa !22
+  %2 = load %struct.StructS** %S.addr, align 8, !tbaa !0
+  %f321 = getelementptr inbounds %struct.StructS* %2, i32 0, i32 1
+  %3 = load i32* %f321, align 4, !tbaa !17
+  ret i32 %3
+}
+
+define i32 @_Z3g11P7StructCP7StructDy(%struct.StructC* %C, %struct.StructD* %D, i64 %count) #0 {
+entry:
+; Access to &(C->b.a.f32) and &(D->b.a.f32).
+; CHECK: Function
+; CHECK: NoAlias:   store i32 4, i32* %f323, align 4, !tbaa !12 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; Remove a load and propogate the value from store.
+; OPT: ret i32 1
+  %C.addr = alloca %struct.StructC*, align 8
+  %D.addr = alloca %struct.StructD*, align 8
+  %count.addr = alloca i64, align 8
+  store %struct.StructC* %C, %struct.StructC** %C.addr, align 8, !tbaa !0
+  store %struct.StructD* %D, %struct.StructD** %D.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructC** %C.addr, align 8, !tbaa !0
+  %b = getelementptr inbounds %struct.StructC* %0, i32 0, i32 1
+  %a = getelementptr inbounds %struct.StructB* %b, i32 0, i32 1
+  %f32 = getelementptr inbounds %struct.StructA* %a, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !23
+  %1 = load %struct.StructD** %D.addr, align 8, !tbaa !0
+  %b1 = getelementptr inbounds %struct.StructD* %1, i32 0, i32 1
+  %a2 = getelementptr inbounds %struct.StructB* %b1, i32 0, i32 1
+  %f323 = getelementptr inbounds %struct.StructA* %a2, i32 0, i32 1
+  store i32 4, i32* %f323, align 4, !tbaa !25
+  %2 = load %struct.StructC** %C.addr, align 8, !tbaa !0
+  %b4 = getelementptr inbounds %struct.StructC* %2, i32 0, i32 1
+  %a5 = getelementptr inbounds %struct.StructB* %b4, i32 0, i32 1
+  %f326 = getelementptr inbounds %struct.StructA* %a5, i32 0, i32 1
+  %3 = load i32* %f326, align 4, !tbaa !23
+  ret i32 %3
+}
+
+define i32 @_Z3g12P7StructCP7StructDy(%struct.StructC* %C, %struct.StructD* %D, i64 %count) #0 {
+entry:
+; Access to &(b1->a.f32) and &(b2->a.f32).
+; CHECK: Function
+; CHECK: MayAlias:   store i32 4, i32* %f325, align 4, !tbaa !6 <->   store i32 1, i32* %f32, align 4, !tbaa !6
+; OPT: define
+; OPT: store i32 1
+; OPT: store i32 4
+; OPT: %[[RET:.*]] = load i32*
+; OPT: ret i32 %[[RET]]
+  %C.addr = alloca %struct.StructC*, align 8
+  %D.addr = alloca %struct.StructD*, align 8
+  %count.addr = alloca i64, align 8
+  %b1 = alloca %struct.StructB*, align 8
+  %b2 = alloca %struct.StructB*, align 8
+  store %struct.StructC* %C, %struct.StructC** %C.addr, align 8, !tbaa !0
+  store %struct.StructD* %D, %struct.StructD** %D.addr, align 8, !tbaa !0
+  store i64 %count, i64* %count.addr, align 8, !tbaa !4
+  %0 = load %struct.StructC** %C.addr, align 8, !tbaa !0
+  %b = getelementptr inbounds %struct.StructC* %0, i32 0, i32 1
+  store %struct.StructB* %b, %struct.StructB** %b1, align 8, !tbaa !0
+  %1 = load %struct.StructD** %D.addr, align 8, !tbaa !0
+  %b3 = getelementptr inbounds %struct.StructD* %1, i32 0, i32 1
+  store %struct.StructB* %b3, %struct.StructB** %b2, align 8, !tbaa !0
+  %2 = load %struct.StructB** %b1, align 8, !tbaa !0
+  %a = getelementptr inbounds %struct.StructB* %2, i32 0, i32 1
+  %f32 = getelementptr inbounds %struct.StructA* %a, i32 0, i32 1
+  store i32 1, i32* %f32, align 4, !tbaa !12
+  %3 = load %struct.StructB** %b2, align 8, !tbaa !0
+  %a4 = getelementptr inbounds %struct.StructB* %3, i32 0, i32 1
+  %f325 = getelementptr inbounds %struct.StructA* %a4, i32 0, i32 1
+  store i32 4, i32* %f325, align 4, !tbaa !12
+  %4 = load %struct.StructB** %b1, align 8, !tbaa !0
+  %a6 = getelementptr inbounds %struct.StructB* %4, i32 0, i32 1
+  %f327 = getelementptr inbounds %struct.StructA* %a6, i32 0, i32 1
+  %5 = load i32* %f327, align 4, !tbaa !12
+  ret i32 %5
+}
+
+attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!0 = metadata !{metadata !1, metadata !1, i64 0}
+!1 = metadata !{metadata !"any pointer", i64 0, metadata !2}
+!2 = metadata !{metadata !"omnipotent char", i64 0, metadata !3}
+!3 = metadata !{metadata !"Simple C/C++ TBAA"}
+!4 = metadata !{metadata !5, metadata !5, i64 0}
+!5 = metadata !{metadata !"long long", i64 0, metadata !2}
+!6 = metadata !{metadata !7, metadata !7, i64 0}
+!7 = metadata !{metadata !"int", i64 0, metadata !2}
+!8 = metadata !{metadata !9, metadata !7, i64 4}
+!9 = metadata !{metadata !"_ZTS7StructA", i64 0, metadata !10, i64 4, metadata !7, i64 8, metadata !10, i64 12, metadata !7}
+!10 = metadata !{metadata !"short", i64 0, metadata !2}
+!11 = metadata !{metadata !9, metadata !10, i64 0}
+!12 = metadata !{metadata !13, metadata !7, i64 8}
+!13 = metadata !{metadata !"_ZTS7StructB", i64 0, metadata !10, i64 4, metadata !9, i64 20, metadata !7}
+!14 = metadata !{metadata !13, metadata !10, i64 4}
+!15 = metadata !{metadata !13, metadata !7, i64 20}
+!16 = metadata !{metadata !13, metadata !7, i64 16}
+!17 = metadata !{metadata !18, metadata !7, i64 4}
+!18 = metadata !{metadata !"_ZTS7StructS", i64 0, metadata !10, i64 4, metadata !7}
+!19 = metadata !{metadata !18, metadata !10, i64 0}
+!20 = metadata !{metadata !21, metadata !7, i64 4}
+!21 = metadata !{metadata !"_ZTS8StructS2", i64 0, metadata !10, i64 4, metadata !7}
+!22 = metadata !{metadata !21, metadata !10, i64 0}
+!23 = metadata !{metadata !24, metadata !7, i64 12}
+!24 = metadata !{metadata !"_ZTS7StructC", i64 0, metadata !10, i64 4, metadata !13, i64 28, metadata !7}
+!25 = metadata !{metadata !26, metadata !7, i64 12}
+!26 = metadata !{metadata !"_ZTS7StructD", i64 0, metadata !10, i64 4, metadata !13, i64 28, metadata !7, i64 32, metadata !2}