* Changes to make NodeType be private to DSNode.
* Add new MultiObject flag to DSNode which keeps track of whether or not
multiple objects have been merged into the node, allowing must-alias info
to be tracked.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6794 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/DataStructure/DataStructureAA.cpp b/lib/Analysis/DataStructure/DataStructureAA.cpp
index 5c3d946..d7c40c6 100644
--- a/lib/Analysis/DataStructure/DataStructureAA.cpp
+++ b/lib/Analysis/DataStructure/DataStructureAA.cpp
@@ -68,15 +68,12 @@
// alias - This is the only method here that does anything interesting...
AliasAnalysis::AliasResult DSAA::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
- // FIXME: This should handle the Size argument as well!
+ if (V1 == V2) return MustAlias;
+
const Function *F1 = getValueFunction(V1);
const Function *F2 = getValueFunction(V2);
assert((!F1 || !F2 || F1 == F2) && "Alias query for 2 different functions?");
-
- // FIXME: This can return must alias if querying a DSNode for a global value
- // where the node has only the G composition bit set, and only one entry in
- // the globals list...
if (F2) F1 = F2;
if (F1) {
// Get the graph for a function...
@@ -88,17 +85,33 @@
hash_map<Value*, DSNodeHandle>::iterator J = GSM.find((Value*)V2);
if (J != GSM.end()) {
assert(J->second.getNode() && "Scalar map points to null node?");
- if (I->second.getNode() != J->second.getNode()) {
- // Return noalias if one of the nodes is complete...
- if ((~I->second.getNode()->NodeType | ~J->second.getNode()->NodeType)
- & DSNode::Incomplete)
- return NoAlias;
- // both are incomplete, they may alias...
- } else {
- // Both point to the same node, see if they point to different
- // offsets... FIXME: This needs to know the size of the alias query
- if (I->second.getOffset() != J->second.getOffset())
- return NoAlias;
+
+ DSNode *N1 = I->second.getNode(), *N2 = J->second.getNode();
+ unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
+
+ // We can only make a judgement of one of the nodes is complete...
+ if (!N1->isIncomplete() || !N2->isIncomplete()) {
+ if (N1 != N2)
+ return NoAlias; // Completely different nodes.
+
+ // Both point to the same node and same offset, and there is only one
+ // physical memory object represented in the node, return must alias.
+ if (O1 == O2 && !N1->isMultiObject())
+ return MustAlias; // Exactly the same object & offset
+
+ // See if they point to different offsets... if so, we may be able to
+ // determine that they do not alias...
+ if (O1 != O2) {
+ if (O2 < O1) { // Ensure that O1 <= O2
+ std::swap(V1, V2);
+ std::swap(O1, O2);
+ std::swap(V1Size, V2Size);
+ }
+
+ // FIXME: This is not correct because we do not handle array
+ // indexing correctly with this check!
+ //if (O1+V1Size <= O2) return NoAlias;
+ }
}
}
}