[llvm] r179337 - Aliasing rules for struct-path aware TBAA.
Manman Ren
mren at apple.com
Thu Apr 11 16:24:18 PDT 2013
Author: mren
Date: Thu Apr 11 18:24:18 2013
New Revision: 179337
URL: http://llvm.org/viewvc/llvm-project?rev=179337&view=rev
Log:
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.
Added:
llvm/trunk/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll
Modified:
llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp?rev=179337&r1=179336&r2=179337&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp Thu Apr 11 18:24:18 2013
@@ -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
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;
@@ -203,6 +278,67 @@ TypeBasedAliasAnalysis::Aliases(const MD
// 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;
+}
+
+/// 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.
Added: llvm/trunk/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll?rev=179337&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll (added)
+++ llvm/trunk/test/Analysis/TypeBasedAliasAnalysis/tbaa-path.ll Thu Apr 11 18:24:18 2013
@@ -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}
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