X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FTypeBasedAliasAnalysis.cpp;h=115872584cb298b1d076630f89eea8d1058872a6;hb=da5f3a3ca5bc534592535d02b2289845461f33db;hp=c14c593bf72e6ccb015871592c3843908b5fb988;hpb=4df1854f263180fcd04cee3347990afe34749a89;p=oota-llvm.git diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp index c14c593bf72..115872584cb 100644 --- a/lib/Analysis/TypeBasedAliasAnalysis.cpp +++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp @@ -16,7 +16,12 @@ // typical C/C++ TBAA, but it can also be used to implement custom alias // analysis behavior for other languages. // -// The current metadata format is very simple. TBAA MDNodes have up to +// We now support two types of metadata format: scalar TBAA and struct-path +// aware TBAA. After all testing cases are upgraded to use struct-path aware +// TBAA and we can auto-upgrade existing bc files, the support for scalar TBAA +// can be dropped. +// +// The scalar TBAA metadata format is very simple. TBAA MDNodes have up to // three fields, e.g.: // !0 = metadata !{ metadata !"an example type tree" } // !1 = metadata !{ metadata !"int", metadata !0 } @@ -40,6 +45,65 @@ // should return true; see // http://llvm.org/docs/AliasAnalysis.html#OtherItfs). // +// With struct-path aware TBAA, the MDNodes attached to an instruction using +// "!tbaa" are called path tag nodes. +// +// The path tag node has 4 fields with the last field being optional. +// +// The first field is the base type node, it can be a struct type node +// or a scalar type node. The second field is the access type node, it +// must be a scalar type node. The third field is the offset into the base type. +// The last field has the same meaning as the last field of our scalar TBAA: +// it's an integer which if equal to 1 indicates that the access is "constant". +// +// The struct type node has a name and a list of pairs, one pair for each member +// of the struct. The first element of each pair is a type node (a struct type +// node or a sclar type node), specifying the type of the member, the second +// element of each pair is the offset of the member. +// +// Given an example +// typedef struct { +// short s; +// } A; +// typedef struct { +// uint16_t s; +// A a; +// } B; +// +// For an acess to B.a.s, we attach !5 (a path tag node) to the load/store +// instruction. The base type is !4 (struct B), the access type is !2 (scalar +// type short) and the offset is 4. +// +// !0 = metadata !{metadata !"Simple C/C++ TBAA"} +// !1 = metadata !{metadata !"omnipotent char", metadata !0} // Scalar type node +// !2 = metadata !{metadata !"short", metadata !1} // Scalar type node +// !3 = metadata !{metadata !"A", metadata !2, i64 0} // Struct type node +// !4 = metadata !{metadata !"B", metadata !2, i64 0, metadata !3, i64 4} +// // Struct type node +// !5 = metadata !{metadata !4, metadata !2, i64 4} // Path tag node +// +// The struct type nodes and the scalar type nodes form a type DAG. +// Root (!0) +// char (!1) -- edge to Root +// short (!2) -- edge to char +// A (!3) -- edge with offset 0 to short +// B (!4) -- edge with offset 0 to short and edge with offset 4 to A +// +// To check if two tags (tagX and tagY) can alias, we start from the base type +// of tagX, follow the edge with the correct offset in the type DAG and adjust +// the offset until we reach the base type of tagY or until we reach the Root +// node. +// If we reach the base type of tagY, compare the adjusted offset with +// offset of tagY, return Alias if the offsets are the same, return NoAlias +// otherwise. +// If we reach the Root node, perform the above starting from base type of tagY +// to see if we reach base type of tagX. +// +// If they have different roots, they're part of different potentially +// unrelated type systems, so we return Alias to be conservative. +// If neither node is an ancestor of the other and they have the same root, +// then we say NoAlias. +// // TODO: The current metadata format doesn't support struct // fields. For example: // struct X { @@ -65,13 +129,13 @@ #include "llvm/IR/Module.h" #include "llvm/Pass.h" #include "llvm/Support/CommandLine.h" +#include "llvm/ADT/SetVector.h" using namespace llvm; // A handy option for disabling TBAA functionality. The same effect can also be // achieved by stripping the !tbaa tags from IR, but this option is sometimes // more convenient. static cl::opt EnableTBAA("enable-tbaa", cl::init(true)); -static cl::opt EnableStructPathTBAA("struct-path-tbaa", cl::init(false)); namespace { /// TBAANode - This is a simple wrapper around an MDNode which provides a @@ -81,7 +145,7 @@ namespace { const MDNode *Node; public: - TBAANode() : Node(0) {} + TBAANode() : Node(nullptr) {} explicit TBAANode(const MDNode *N) : Node(N) {} /// getNode - Get the MDNode for this TBAANode. @@ -104,7 +168,7 @@ namespace { bool TypeIsImmutable() const { if (Node->getNumOperands() < 3) return false; - ConstantInt *CI = dyn_cast(Node->getOperand(2)); + ConstantInt *CI = mdconst::dyn_extract(Node->getOperand(2)); if (!CI) return false; return CI->getValue()[0]; @@ -119,7 +183,6 @@ namespace { const MDNode *Node; public: - TBAAStructTagNode() : Node(0) {} explicit TBAAStructTagNode(const MDNode *N) : Node(N) {} /// Get the MDNode for this TBAAStructTagNode. @@ -132,7 +195,18 @@ namespace { return dyn_cast_or_null(Node->getOperand(1)); } uint64_t getOffset() const { - return cast(Node->getOperand(2))->getZExtValue(); + return mdconst::extract(Node->getOperand(2))->getZExtValue(); + } + /// TypeIsImmutable - Test if this TBAAStructTagNode represents a type for + /// objects which are not modified (by any means) in the context where this + /// AliasAnalysis is relevant. + bool TypeIsImmutable() const { + if (Node->getNumOperands() < 4) + return false; + ConstantInt *CI = mdconst::dyn_extract(Node->getOperand(3)); + if (!CI) + return false; + return CI->getValue()[0]; } }; @@ -144,7 +218,7 @@ namespace { const MDNode *Node; public: - TBAAStructTypeNode() : Node(0) {} + TBAAStructTypeNode() : Node(nullptr) {} explicit TBAAStructTypeNode(const MDNode *N) : Node(N) {} /// Get the MDNode for this TBAAStructTypeNode. @@ -153,14 +227,30 @@ namespace { /// 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 { + // Parent can be omitted for the root node. if (Node->getNumOperands() < 2) return TBAAStructTypeNode(); + // Fast path for a scalar type node and a struct type node with a single + // field. + if (Node->getNumOperands() <= 3) { + uint64_t Cur = Node->getNumOperands() == 2 + ? 0 + : mdconst::extract(Node->getOperand(2)) + ->getZExtValue(); + Offset -= Cur; + MDNode *P = dyn_cast_or_null(Node->getOperand(1)); + if (!P) + return TBAAStructTypeNode(); + return TBAAStructTypeNode(P); + } + // 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(Node->getOperand(Idx))->getZExtValue(); + uint64_t Cur = mdconst::extract(Node->getOperand(Idx + 1)) + ->getZExtValue(); if (Cur > Offset) { assert(Idx >= 3 && "TBAAStructTypeNode::getParent should have an offset match!"); @@ -171,10 +261,10 @@ namespace { // Move along the last field. if (TheIdx == 0) TheIdx = Node->getNumOperands() - 2; - uint64_t Cur = cast(Node->getOperand(TheIdx))-> - getZExtValue(); + uint64_t Cur = mdconst::extract(Node->getOperand(TheIdx + 1)) + ->getZExtValue(); Offset -= Cur; - MDNode *P = dyn_cast_or_null(Node->getOperand(TheIdx + 1)); + MDNode *P = dyn_cast_or_null(Node->getOperand(TheIdx)); if (!P) return TBAAStructTypeNode(); return TBAAStructTypeNode(P); @@ -193,15 +283,13 @@ namespace { initializeTypeBasedAliasAnalysisPass(*PassRegistry::getPassRegistry()); } - virtual void initializePass() { - InitializeAliasAnalysis(this); - } + bool doInitialization(Module &M) override; /// getAdjustedAnalysisPointer - This method is used when a pass implements /// an analysis interface through multiple inheritance. If needed, it /// should override this to adjust the this pointer as needed for the /// specified pass info. - virtual void *getAdjustedAnalysisPointer(const void *PI) { + void *getAdjustedAnalysisPointer(const void *PI) override { if (PI == &AliasAnalysis::ID) return (AliasAnalysis*)this; return this; @@ -211,15 +299,15 @@ namespace { bool PathAliases(const MDNode *A, const MDNode *B) const; private: - virtual void getAnalysisUsage(AnalysisUsage &AU) const; - virtual AliasResult alias(const Location &LocA, const Location &LocB); - virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal); - virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS); - virtual ModRefBehavior getModRefBehavior(const Function *F); - virtual ModRefResult getModRefInfo(ImmutableCallSite CS, - const Location &Loc); - virtual ModRefResult getModRefInfo(ImmutableCallSite CS1, - ImmutableCallSite CS2); + void getAnalysisUsage(AnalysisUsage &AU) const override; + AliasResult alias(const Location &LocA, const Location &LocB) override; + bool pointsToConstantMemory(const Location &Loc, bool OrLocal) override; + ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override; + ModRefBehavior getModRefBehavior(const Function *F) override; + ModRefResult getModRefInfo(ImmutableCallSite CS, + const Location &Loc) override; + ModRefResult getModRefInfo(ImmutableCallSite CS1, + ImmutableCallSite CS2) override; }; } // End of anonymous namespace @@ -232,18 +320,33 @@ ImmutablePass *llvm::createTypeBasedAliasAnalysisPass() { return new TypeBasedAliasAnalysis(); } +bool TypeBasedAliasAnalysis::doInitialization(Module &M) { + InitializeAliasAnalysis(this, &M.getDataLayout()); + return true; +} + void TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesAll(); AliasAnalysis::getAnalysisUsage(AU); } +/// Check the first operand of the tbaa tag node, if it is a MDNode, we treat +/// it as struct-path aware TBAA format, otherwise, we treat it as scalar TBAA +/// format. +static bool isStructPathTBAA(const MDNode *MD) { + // Anonymous TBAA root starts with a MDNode and dragonegg uses it as + // a TBAA tag. + return isa(MD->getOperand(0)) && MD->getNumOperands() >= 3; +} + /// Aliases - Test whether the type represented by A may alias the /// type represented by B. bool TypeBasedAliasAnalysis::Aliases(const MDNode *A, const MDNode *B) const { - if (EnableStructPathTBAA) + // Make sure that both MDNodes are struct-path aware. + if (isStructPathTBAA(A) && isStructPathTBAA(B)) return PathAliases(A, B); // Keep track of the root node for A and B. @@ -289,6 +392,10 @@ TypeBasedAliasAnalysis::Aliases(const MDNode *A, bool TypeBasedAliasAnalysis::PathAliases(const MDNode *A, const MDNode *B) const { + // Verify that both input nodes are struct-path aware. + assert(isStructPathTBAA(A) && "MDNode A is not struct-path aware."); + assert(isStructPathTBAA(B) && "MDNode B is not struct-path aware."); + // Keep track of the root node for A and B. TBAAStructTypeNode RootA, RootB; TBAAStructTagNode TagA(A), TagB(B); @@ -353,9 +460,9 @@ TypeBasedAliasAnalysis::alias(const Location &LocA, // Get the attached MDNodes. If either value lacks a tbaa MDNode, we must // be conservative. - const MDNode *AM = LocA.TBAATag; + const MDNode *AM = LocA.AATags.TBAA; if (!AM) return AliasAnalysis::alias(LocA, LocB); - const MDNode *BM = LocB.TBAATag; + const MDNode *BM = LocB.AATags.TBAA; if (!BM) return AliasAnalysis::alias(LocA, LocB); // If they may alias, chain to the next AliasAnalysis. @@ -371,12 +478,13 @@ bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc, if (!EnableTBAA) return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); - const MDNode *M = Loc.TBAATag; + const MDNode *M = Loc.AATags.TBAA; if (!M) return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); // If this is an "immutable" type, we can assume the pointer is pointing // to constant memory. - if (TBAANode(M).TypeIsImmutable()) + if ((!isStructPathTBAA(M) && TBAANode(M).TypeIsImmutable()) || + (isStructPathTBAA(M) && TBAAStructTagNode(M).TypeIsImmutable())) return true; return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); @@ -392,7 +500,8 @@ TypeBasedAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) { // If this is an "immutable" type, we can assume the call doesn't write // to memory. if (const MDNode *M = CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) - if (TBAANode(M).TypeIsImmutable()) + if ((!isStructPathTBAA(M) && TBAANode(M).TypeIsImmutable()) || + (isStructPathTBAA(M) && TBAAStructTagNode(M).TypeIsImmutable())) Min = OnlyReadsMemory; return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min); @@ -410,9 +519,9 @@ TypeBasedAliasAnalysis::getModRefInfo(ImmutableCallSite CS, if (!EnableTBAA) return AliasAnalysis::getModRefInfo(CS, Loc); - if (const MDNode *L = Loc.TBAATag) + if (const MDNode *L = Loc.AATags.TBAA) if (const MDNode *M = - CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) + CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) if (!Aliases(L, M)) return NoModRef; @@ -426,11 +535,111 @@ TypeBasedAliasAnalysis::getModRefInfo(ImmutableCallSite CS1, return AliasAnalysis::getModRefInfo(CS1, CS2); if (const MDNode *M1 = - CS1.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) + CS1.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) if (const MDNode *M2 = - CS2.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) + CS2.getInstruction()->getMetadata(LLVMContext::MD_tbaa)) if (!Aliases(M1, M2)) return NoModRef; return AliasAnalysis::getModRefInfo(CS1, CS2); } + +bool MDNode::isTBAAVtableAccess() const { + if (!isStructPathTBAA(this)) { + if (getNumOperands() < 1) return false; + if (MDString *Tag1 = dyn_cast(getOperand(0))) { + if (Tag1->getString() == "vtable pointer") return true; + } + return false; + } + + // For struct-path aware TBAA, we use the access type of the tag. + if (getNumOperands() < 2) return false; + MDNode *Tag = cast_or_null(getOperand(1)); + if (!Tag) return false; + if (MDString *Tag1 = dyn_cast(Tag->getOperand(0))) { + if (Tag1->getString() == "vtable pointer") return true; + } + return false; +} + +MDNode *MDNode::getMostGenericTBAA(MDNode *A, MDNode *B) { + if (!A || !B) + return nullptr; + + if (A == B) + return A; + + // For struct-path aware TBAA, we use the access type of the tag. + bool StructPath = isStructPathTBAA(A) && isStructPathTBAA(B); + if (StructPath) { + A = cast_or_null(A->getOperand(1)); + if (!A) return nullptr; + B = cast_or_null(B->getOperand(1)); + if (!B) return nullptr; + } + + SmallSetVector PathA; + MDNode *T = A; + while (T) { + if (PathA.count(T)) + report_fatal_error("Cycle found in TBAA metadata."); + PathA.insert(T); + T = T->getNumOperands() >= 2 ? cast_or_null(T->getOperand(1)) + : nullptr; + } + + SmallSetVector PathB; + T = B; + while (T) { + if (PathB.count(T)) + report_fatal_error("Cycle found in TBAA metadata."); + PathB.insert(T); + T = T->getNumOperands() >= 2 ? cast_or_null(T->getOperand(1)) + : nullptr; + } + + int IA = PathA.size() - 1; + int IB = PathB.size() - 1; + + MDNode *Ret = nullptr; + while (IA >= 0 && IB >=0) { + if (PathA[IA] == PathB[IB]) + Ret = PathA[IA]; + else + break; + --IA; + --IB; + } + if (!StructPath) + return Ret; + + if (!Ret) + return nullptr; + // We need to convert from a type node to a tag node. + Type *Int64 = IntegerType::get(A->getContext(), 64); + Metadata *Ops[3] = {Ret, Ret, + ConstantAsMetadata::get(ConstantInt::get(Int64, 0))}; + return MDNode::get(A->getContext(), Ops); +} + +void Instruction::getAAMetadata(AAMDNodes &N, bool Merge) const { + if (Merge) + N.TBAA = + MDNode::getMostGenericTBAA(N.TBAA, getMetadata(LLVMContext::MD_tbaa)); + else + N.TBAA = getMetadata(LLVMContext::MD_tbaa); + + if (Merge) + N.Scope = MDNode::getMostGenericAliasScope( + N.Scope, getMetadata(LLVMContext::MD_alias_scope)); + else + N.Scope = getMetadata(LLVMContext::MD_alias_scope); + + if (Merge) + N.NoAlias = + MDNode::intersect(N.NoAlias, getMetadata(LLVMContext::MD_noalias)); + else + N.NoAlias = getMetadata(LLVMContext::MD_noalias); +} +