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Factor out the main aliasing check into a separate function.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116958 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-10-20 22:11:14 +00:00
parent 561ac17d20
commit ba13864483
1 changed files with 50 additions and 35 deletions
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85
lib/Analysis/TypeBasedAliasAnalysis.cpp
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@ -103,6 +103,8 @@ namespace {
return this; return this;
} }
bool Aliases(const MDNode *A, const MDNode *B) const;
private: private:
virtual void getAnalysisUsage(AnalysisUsage &AU) const; virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual AliasResult alias(const Location &LocA, const Location &LocB); virtual AliasResult alias(const Location &LocA, const Location &LocB);
@ -125,6 +127,49 @@ TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
AliasAnalysis::getAnalysisUsage(AU); AliasAnalysis::getAnalysisUsage(AU);
} }
/// 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(A); ; ) {
if (T.getNode() == B)
// B is an ancestor of A.
return true;
RootA = T;
T = T.getParent();
if (!T.getNode())
break;
}
// Climb the tree from B to see if we reach A.
for (TBAANode T(B); ; ) {
if (T.getNode() == A)
// A is an ancestor of B.
return true;
RootB = T;
T = T.getParent();
if (!T.getNode())
break;
}
// Neither node is an ancestor of the other.
// If they have different roots, they're part of different potentially
// unrelated type systems, so we must be conservative.
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 AliasAnalysis::AliasResult
TypeBasedAliasAnalysis::alias(const Location &LocA, TypeBasedAliasAnalysis::alias(const Location &LocA,
const Location &LocB) { const Location &LocB) {
@ -138,42 +183,12 @@ TypeBasedAliasAnalysis::alias(const Location &LocA,
const MDNode *BM = LocB.TBAATag; const MDNode *BM = LocB.TBAATag;
if (!BM) return AliasAnalysis::alias(LocA, LocB); if (!BM) return AliasAnalysis::alias(LocA, LocB);
// Keep track of the root node for A and B. // If they may alias, chain to the next AliasAnalysis.
TBAANode RootA, RootB; if (Aliases(AM, BM))
return AliasAnalysis::alias(LocA, LocB);
// Climb the tree from A to see if we reach B. // Otherwise return a definitive result.
for (TBAANode T(AM); ; ) { return NoAlias;
if (T.getNode() == BM)
// B is an ancestor of A.
return AliasAnalysis::alias(LocA, LocB);
RootA = T;
T = T.getParent();
if (!T.getNode())
break;
}
// Climb the tree from B to see if we reach A.
for (TBAANode T(BM); ; ) {
if (T.getNode() == AM)
// A is an ancestor of B.
return AliasAnalysis::alias(LocA, LocB);
RootB = T;
T = T.getParent();
if (!T.getNode())
break;
}
// 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);
} }
bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) { bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) {