// This file defines the ScopedNoAlias alias-analysis pass, which implements
// metadata-based scoped no-alias support.
//
-// Alias-analysis scopes are defined similar to TBAA nodes:
+// 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.
//
-// !scope0 = metadata !{ metadata !"scope of foo()" }
-// !scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
-// !scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
-// !scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
-// !scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }
+// !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 %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }
//
// When evaluating an aliasing query, if one of the instructions is associated
-// with an alias.scope id that is identical to the noalias scope associated
-// with the other instruction, or is a descendant (in the scope hierarchy) of
-// the noalias scope associated with the other instruction, then the two memory
+// 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.
//
-// Note that if the first element of the scope metadata is a string, then it
-// can be combined accross functions and translation units. The string can be
-// replaced by a self-reference to create globally unqiue scope identifiers.
-//
//===----------------------------------------------------------------------===//
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/Constants.h"
/// getNode - Get the MDNode for this AliasScopeNode.
const MDNode *getNode() const { return Node; }
- /// getParent - Get this AliasScopeNode's Alias tree parent.
- AliasScopeNode getParent() const {
+ /// getDomain - Get the MDNode for this AliasScopeNode's domain.
+ const MDNode *getDomain() const {
if (Node->getNumOperands() < 2)
- return AliasScopeNode();
- MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(1));
- if (!P)
- return AliasScopeNode();
- // Ok, this node has a valid parent. Return it.
- return AliasScopeNode(P);
+ return nullptr;
+ return dyn_cast_or_null<MDNode>(Node->getOperand(1));
}
};
initializeScopedNoAliasAAPass(*PassRegistry::getPassRegistry());
}
- virtual void initializePass() {
- InitializeAliasAnalysis(this);
- }
+ void initializePass() override { InitializeAliasAnalysis(this); }
/// 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;
}
protected:
- bool mayAlias(const MDNode *A, const MDNode *B) const;
bool mayAliasInScopes(const MDNode *Scopes, const MDNode *NoAlias) const;
+ void collectMDInDomain(const MDNode *List, const MDNode *Domain,
+ SmallPtrSetImpl<const MDNode *> &Nodes) 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
AliasAnalysis::getAnalysisUsage(AU);
}
-/// mayAlias - Test whether the scope represented by A may alias the
-/// scope represented by B. Specifically, A is the target scope, and B is the
-/// noalias scope.
-bool
-ScopedNoAliasAA::mayAlias(const MDNode *A,
- const MDNode *B) const {
- // Climb the tree from A to see if we reach B.
- for (AliasScopeNode T(A); ; ) {
- if (T.getNode() == B)
- // B is an ancestor of A.
- return false;
-
- T = T.getParent();
- if (!T.getNode())
- break;
- }
-
- return true;
+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
if (!Scopes || !NoAlias)
return true;
- for (unsigned i = 0, ie = Scopes->getNumOperands(); i != ie; ++i)
- if (const MDNode *SMD = dyn_cast<MDNode>(Scopes->getOperand(i)))
- for (unsigned j = 0, je = NoAlias->getNumOperands(); j != je; ++j)
- if (const MDNode *NAMD = dyn_cast<MDNode>(NoAlias->getOperand(j)))
- if (!mayAlias(SMD, NAMD))
- return false;
+ // 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;
+ return true;
}
AliasAnalysis::AliasResult
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