| //===- ScopedNoAliasAA.cpp - Scoped No-Alias Alias Analysis ---------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the ScopedNoAlias alias-analysis pass, which implements |
| // metadata-based scoped no-alias support. |
| // |
| // Alias-analysis scopes are defined by an id (which can be a string or some |
| // other metadata node), a domain node, and an optional descriptive string. |
| // A domain is defined by an id (which can be a string or some other metadata |
| // node), and an optional descriptive string. |
| // |
| // !dom0 = metadata !{ metadata !"domain of foo()" } |
| // !scope1 = metadata !{ metadata !scope1, metadata !dom0, metadata !"scope 1" } |
| // !scope2 = metadata !{ metadata !scope2, metadata !dom0, metadata !"scope 2" } |
| // |
| // Loads and stores can be tagged with an alias-analysis scope, and also, with |
| // a noalias tag for a specific scope: |
| // |
| // ... = load %ptr1, !alias.scope !{ !scope1 } |
| // ... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 } |
| // |
| // When evaluating an aliasing query, if one of the instructions is associated |
| // has a set of noalias scopes in some domain that is superset of the alias |
| // scopes in that domain of some other instruction, then the two memory |
| // accesses are assumed not to alias. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/Passes.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Metadata.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| using namespace llvm; |
| |
| // A handy option for disabling scoped no-alias functionality. The same effect |
| // can also be achieved by stripping the associated metadata tags from IR, but |
| // this option is sometimes more convenient. |
| static cl::opt<bool> |
| EnableScopedNoAlias("enable-scoped-noalias", cl::init(true)); |
| |
| namespace { |
| /// AliasScopeNode - 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 AliasScopeNode { |
| const MDNode *Node; |
| |
| public: |
| AliasScopeNode() : Node(0) {} |
| explicit AliasScopeNode(const MDNode *N) : Node(N) {} |
| |
| /// getNode - Get the MDNode for this AliasScopeNode. |
| const MDNode *getNode() const { return Node; } |
| |
| /// getDomain - Get the MDNode for this AliasScopeNode's domain. |
| const MDNode *getDomain() const { |
| if (Node->getNumOperands() < 2) |
| return nullptr; |
| return dyn_cast_or_null<MDNode>(Node->getOperand(1)); |
| } |
| }; |
| |
| /// ScopedNoAliasAA - This is a simple alias analysis |
| /// implementation that uses scoped-noalias metadata to answer queries. |
| class ScopedNoAliasAA : public ImmutablePass, public AliasAnalysis { |
| public: |
| static char ID; // Class identification, replacement for typeinfo |
| ScopedNoAliasAA() : ImmutablePass(ID) { |
| initializeScopedNoAliasAAPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| 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. |
| void *getAdjustedAnalysisPointer(const void *PI) override { |
| if (PI == &AliasAnalysis::ID) |
| return (AliasAnalysis*)this; |
| return this; |
| } |
| |
| protected: |
| bool mayAliasInScopes(const MDNode *Scopes, const MDNode *NoAlias) const; |
| void collectMDInDomain(const MDNode *List, const MDNode *Domain, |
| SmallPtrSetImpl<const MDNode *> &Nodes) const; |
| |
| private: |
| void getAnalysisUsage(AnalysisUsage &AU) const override; |
| AliasResult alias(const MemoryLocation &LocA, |
| const MemoryLocation &LocB) override; |
| bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal) override; |
| ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override; |
| ModRefBehavior getModRefBehavior(const Function *F) override; |
| ModRefResult getModRefInfo(ImmutableCallSite CS, |
| const MemoryLocation &Loc) override; |
| ModRefResult getModRefInfo(ImmutableCallSite CS1, |
| ImmutableCallSite CS2) override; |
| }; |
| } // End of anonymous namespace |
| |
| // Register this pass... |
| char ScopedNoAliasAA::ID = 0; |
| INITIALIZE_AG_PASS(ScopedNoAliasAA, AliasAnalysis, "scoped-noalias", |
| "Scoped NoAlias Alias Analysis", false, true, false) |
| |
| ImmutablePass *llvm::createScopedNoAliasAAPass() { |
| return new ScopedNoAliasAA(); |
| } |
| |
| bool ScopedNoAliasAA::doInitialization(Module &M) { |
| InitializeAliasAnalysis(this, &M.getDataLayout()); |
| return true; |
| } |
| |
| void |
| ScopedNoAliasAA::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesAll(); |
| AliasAnalysis::getAnalysisUsage(AU); |
| } |
| |
| void |
| ScopedNoAliasAA::collectMDInDomain(const MDNode *List, const MDNode *Domain, |
| SmallPtrSetImpl<const MDNode *> &Nodes) const { |
| for (unsigned i = 0, ie = List->getNumOperands(); i != ie; ++i) |
| if (const MDNode *MD = dyn_cast<MDNode>(List->getOperand(i))) |
| if (AliasScopeNode(MD).getDomain() == Domain) |
| Nodes.insert(MD); |
| } |
| |
| bool |
| ScopedNoAliasAA::mayAliasInScopes(const MDNode *Scopes, |
| const MDNode *NoAlias) const { |
| if (!Scopes || !NoAlias) |
| return true; |
| |
| // Collect the set of scope domains relevant to the noalias scopes. |
| SmallPtrSet<const MDNode *, 16> Domains; |
| for (unsigned i = 0, ie = NoAlias->getNumOperands(); i != ie; ++i) |
| if (const MDNode *NAMD = dyn_cast<MDNode>(NoAlias->getOperand(i))) |
| if (const MDNode *Domain = AliasScopeNode(NAMD).getDomain()) |
| Domains.insert(Domain); |
| |
| // We alias unless, for some domain, the set of noalias scopes in that domain |
| // is a superset of the set of alias scopes in that domain. |
| for (const MDNode *Domain : Domains) { |
| SmallPtrSet<const MDNode *, 16> NANodes, ScopeNodes; |
| collectMDInDomain(NoAlias, Domain, NANodes); |
| collectMDInDomain(Scopes, Domain, ScopeNodes); |
| if (!ScopeNodes.size()) |
| continue; |
| |
| // To not alias, all of the nodes in ScopeNodes must be in NANodes. |
| bool FoundAll = true; |
| for (const MDNode *SMD : ScopeNodes) |
| if (!NANodes.count(SMD)) { |
| FoundAll = false; |
| break; |
| } |
| |
| if (FoundAll) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| AliasResult ScopedNoAliasAA::alias(const MemoryLocation &LocA, |
| const MemoryLocation &LocB) { |
| if (!EnableScopedNoAlias) |
| return AliasAnalysis::alias(LocA, LocB); |
| |
| // Get the attached MDNodes. |
| const MDNode *AScopes = LocA.AATags.Scope, |
| *BScopes = LocB.AATags.Scope; |
| |
| const MDNode *ANoAlias = LocA.AATags.NoAlias, |
| *BNoAlias = LocB.AATags.NoAlias; |
| |
| if (!mayAliasInScopes(AScopes, BNoAlias)) |
| return NoAlias; |
| |
| if (!mayAliasInScopes(BScopes, ANoAlias)) |
| return NoAlias; |
| |
| // If they may alias, chain to the next AliasAnalysis. |
| return AliasAnalysis::alias(LocA, LocB); |
| } |
| |
| bool ScopedNoAliasAA::pointsToConstantMemory(const MemoryLocation &Loc, |
| bool OrLocal) { |
| return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); |
| } |
| |
| AliasAnalysis::ModRefBehavior |
| ScopedNoAliasAA::getModRefBehavior(ImmutableCallSite CS) { |
| return AliasAnalysis::getModRefBehavior(CS); |
| } |
| |
| AliasAnalysis::ModRefBehavior |
| ScopedNoAliasAA::getModRefBehavior(const Function *F) { |
| return AliasAnalysis::getModRefBehavior(F); |
| } |
| |
| AliasAnalysis::ModRefResult |
| ScopedNoAliasAA::getModRefInfo(ImmutableCallSite CS, |
| const MemoryLocation &Loc) { |
| if (!EnableScopedNoAlias) |
| return AliasAnalysis::getModRefInfo(CS, Loc); |
| |
| if (!mayAliasInScopes(Loc.AATags.Scope, CS.getInstruction()->getMetadata( |
| LLVMContext::MD_noalias))) |
| return NoModRef; |
| |
| if (!mayAliasInScopes( |
| CS.getInstruction()->getMetadata(LLVMContext::MD_alias_scope), |
| Loc.AATags.NoAlias)) |
| return NoModRef; |
| |
| return AliasAnalysis::getModRefInfo(CS, Loc); |
| } |
| |
| AliasAnalysis::ModRefResult |
| ScopedNoAliasAA::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { |
| if (!EnableScopedNoAlias) |
| return AliasAnalysis::getModRefInfo(CS1, CS2); |
| |
| if (!mayAliasInScopes( |
| CS1.getInstruction()->getMetadata(LLVMContext::MD_alias_scope), |
| CS2.getInstruction()->getMetadata(LLVMContext::MD_noalias))) |
| return NoModRef; |
| |
| if (!mayAliasInScopes( |
| CS2.getInstruction()->getMetadata(LLVMContext::MD_alias_scope), |
| CS1.getInstruction()->getMetadata(LLVMContext::MD_noalias))) |
| return NoModRef; |
| |
| return AliasAnalysis::getModRefInfo(CS1, CS2); |
| } |
| |