| //===- ScopedNoAliasAA.cpp - Scoped No-Alias Alias Analysis ---------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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 a superset of the alias |
| // scopes in that domain of some other instruction, then the two memory |
| // accesses are assumed not to alias. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/ScopedNoAliasAA.h" |
| #include "llvm/ADT/SetOperations.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/Analysis/MemoryLocation.h" |
| #include "llvm/IR/InstrTypes.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Metadata.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/Casting.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), cl::Hidden); |
| |
| AliasResult ScopedNoAliasAAResult::alias(const MemoryLocation &LocA, |
| const MemoryLocation &LocB, |
| AAQueryInfo &AAQI) { |
| if (!EnableScopedNoAlias) |
| return AAResultBase::alias(LocA, LocB, AAQI); |
| |
| // 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 AliasResult::NoAlias; |
| |
| if (!mayAliasInScopes(BScopes, ANoAlias)) |
| return AliasResult::NoAlias; |
| |
| // If they may alias, chain to the next AliasAnalysis. |
| return AAResultBase::alias(LocA, LocB, AAQI); |
| } |
| |
| ModRefInfo ScopedNoAliasAAResult::getModRefInfo(const CallBase *Call, |
| const MemoryLocation &Loc, |
| AAQueryInfo &AAQI) { |
| if (!EnableScopedNoAlias) |
| return AAResultBase::getModRefInfo(Call, Loc, AAQI); |
| |
| if (!mayAliasInScopes(Loc.AATags.Scope, |
| Call->getMetadata(LLVMContext::MD_noalias))) |
| return ModRefInfo::NoModRef; |
| |
| if (!mayAliasInScopes(Call->getMetadata(LLVMContext::MD_alias_scope), |
| Loc.AATags.NoAlias)) |
| return ModRefInfo::NoModRef; |
| |
| return AAResultBase::getModRefInfo(Call, Loc, AAQI); |
| } |
| |
| ModRefInfo ScopedNoAliasAAResult::getModRefInfo(const CallBase *Call1, |
| const CallBase *Call2, |
| AAQueryInfo &AAQI) { |
| if (!EnableScopedNoAlias) |
| return AAResultBase::getModRefInfo(Call1, Call2, AAQI); |
| |
| if (!mayAliasInScopes(Call1->getMetadata(LLVMContext::MD_alias_scope), |
| Call2->getMetadata(LLVMContext::MD_noalias))) |
| return ModRefInfo::NoModRef; |
| |
| if (!mayAliasInScopes(Call2->getMetadata(LLVMContext::MD_alias_scope), |
| Call1->getMetadata(LLVMContext::MD_noalias))) |
| return ModRefInfo::NoModRef; |
| |
| return AAResultBase::getModRefInfo(Call1, Call2, AAQI); |
| } |
| |
| static void collectMDInDomain(const MDNode *List, const MDNode *Domain, |
| SmallPtrSetImpl<const MDNode *> &Nodes) { |
| for (const MDOperand &MDOp : List->operands()) |
| if (const MDNode *MD = dyn_cast<MDNode>(MDOp)) |
| if (AliasScopeNode(MD).getDomain() == Domain) |
| Nodes.insert(MD); |
| } |
| |
| bool ScopedNoAliasAAResult::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 (const MDOperand &MDOp : NoAlias->operands()) |
| if (const MDNode *NAMD = dyn_cast<MDNode>(MDOp)) |
| 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> ScopeNodes; |
| collectMDInDomain(Scopes, Domain, ScopeNodes); |
| if (ScopeNodes.empty()) |
| continue; |
| |
| SmallPtrSet<const MDNode *, 16> NANodes; |
| collectMDInDomain(NoAlias, Domain, NANodes); |
| |
| // To not alias, all of the nodes in ScopeNodes must be in NANodes. |
| if (llvm::set_is_subset(ScopeNodes, NANodes)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| AnalysisKey ScopedNoAliasAA::Key; |
| |
| ScopedNoAliasAAResult ScopedNoAliasAA::run(Function &F, |
| FunctionAnalysisManager &AM) { |
| return ScopedNoAliasAAResult(); |
| } |
| |
| char ScopedNoAliasAAWrapperPass::ID = 0; |
| |
| INITIALIZE_PASS(ScopedNoAliasAAWrapperPass, "scoped-noalias-aa", |
| "Scoped NoAlias Alias Analysis", false, true) |
| |
| ImmutablePass *llvm::createScopedNoAliasAAWrapperPass() { |
| return new ScopedNoAliasAAWrapperPass(); |
| } |
| |
| ScopedNoAliasAAWrapperPass::ScopedNoAliasAAWrapperPass() : ImmutablePass(ID) { |
| initializeScopedNoAliasAAWrapperPassPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool ScopedNoAliasAAWrapperPass::doInitialization(Module &M) { |
| Result.reset(new ScopedNoAliasAAResult()); |
| return false; |
| } |
| |
| bool ScopedNoAliasAAWrapperPass::doFinalization(Module &M) { |
| Result.reset(); |
| return false; |
| } |
| |
| void ScopedNoAliasAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesAll(); |
| } |