[llvm-commits] [llvm] r116958 - /llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
Dan Gohman
gohman at apple.com
Wed Oct 20 15:11:14 PDT 2010
Author: djg
Date: Wed Oct 20 17:11:14 2010
New Revision: 116958
URL: http://llvm.org/viewvc/llvm-project?rev=116958&view=rev
Log:
Factor out the main aliasing check into a separate function.
Modified:
llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp?rev=116958&r1=116957&r2=116958&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/TypeBasedAliasAnalysis.cpp Wed Oct 20 17:11:14 2010
@@ -103,6 +103,8 @@
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 @@
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 @@
}
// 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 @@
// 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) {
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