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Factor out the main aliasing check into a separate function. 

llvm-svn: 116958
This commit is contained in:
Dan Gohman 2010-10-20 22:11:14 +00:00
parent 55a028680c
commit a2ab75bc8d
1 changed files with 50 additions and 35 deletions
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85
llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
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@ -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);
@ -125,6 +127,49 @@ TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
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
TypeBasedAliasAnalysis::alias(const Location &LocA,
const Location &LocB) {
@ -138,42 +183,12 @@ TypeBasedAliasAnalysis::alias(const Location &LocA,
const MDNode *BM = LocB.TBAATag;
if (!BM) return AliasAnalysis::alias(LocA, LocB);
// Keep track of the root node for A and B.
TBAANode RootA, RootB;
// If they may alias, chain to the next AliasAnalysis.
if (Aliases(AM, BM))
return AliasAnalysis::alias(LocA, LocB);
// Climb the tree from A to see if we reach B.
for (TBAANode T(AM); ; ) {
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);
// Otherwise return a definitive result.
return NoAlias;
}
bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) {