diff options
| -rw-r--r-- | llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp | 63 |
1 files changed, 39 insertions, 24 deletions
diff --git a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp index 787db7351aa..5994ffd702f 100644 --- a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp +++ b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp @@ -103,6 +103,8 @@ namespace { return this; } + bool Aliases(const MDNode *A, const MDNode *B) const; + private: virtual void getAnalysisUsage(AnalysisUsage &AU) const; virtual AliasResult alias(const Location &LocA, const Location &LocB); @@ -125,27 +127,19 @@ TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { AliasAnalysis::getAnalysisUsage(AU); } -AliasAnalysis::AliasResult -TypeBasedAliasAnalysis::alias(const Location &LocA, - const Location &LocB) { - if (!EnableTBAA) - return AliasAnalysis::alias(LocA, LocB); - - // Get the attached MDNodes. If either value lacks a tbaa MDNode, we must - // be conservative. - const MDNode *AM = LocA.TBAATag; - if (!AM) return AliasAnalysis::alias(LocA, LocB); - const MDNode *BM = LocB.TBAATag; - if (!BM) return AliasAnalysis::alias(LocA, LocB); - +/// 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 { // Keep track of the root node for A and B. TBAANode RootA, RootB; // Climb the tree from A to see if we reach B. - for (TBAANode T(AM); ; ) { - if (T.getNode() == BM) + for (TBAANode T(A); ; ) { + if (T.getNode() == B) // B is an ancestor of A. - return AliasAnalysis::alias(LocA, LocB); + return true; RootA = T; T = T.getParent(); @@ -154,10 +148,10 @@ TypeBasedAliasAnalysis::alias(const Location &LocA, } // Climb the tree from B to see if we reach A. - for (TBAANode T(BM); ; ) { - if (T.getNode() == AM) + for (TBAANode T(B); ; ) { + if (T.getNode() == A) // A is an ancestor of B. - return AliasAnalysis::alias(LocA, LocB); + return true; RootB = T; T = T.getParent(); @@ -167,13 +161,34 @@ TypeBasedAliasAnalysis::alias(const Location &LocA, // Neither node is an ancestor of the other. - // If they have the same root, then we've proved there's no alias. - if (RootA.getNode() == RootB.getNode()) - return NoAlias; - // If they have different roots, they're part of different potentially // unrelated type systems, so we must be conservative. - return AliasAnalysis::alias(LocA, LocB); + if (RootA.getNode() != RootB.getNode()) + return true; + + // If they have the same root, then we've proved there's no alias. + return false; +} + +AliasAnalysis::AliasResult +TypeBasedAliasAnalysis::alias(const Location &LocA, + const Location &LocB) { + if (!EnableTBAA) + return AliasAnalysis::alias(LocA, LocB); + + // Get the attached MDNodes. If either value lacks a tbaa MDNode, we must + // be conservative. + const MDNode *AM = LocA.TBAATag; + if (!AM) return AliasAnalysis::alias(LocA, LocB); + const MDNode *BM = LocB.TBAATag; + if (!BM) return AliasAnalysis::alias(LocA, LocB); + + // If they may alias, chain to the next AliasAnalysis. + if (Aliases(AM, BM)) + return AliasAnalysis::alias(LocA, LocB); + + // Otherwise return a definitive result. + return NoAlias; } bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) { |
