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Make -steens-aa more conservative (aka correct) by making sure to obey 

incompleteness flags.

Make it more aggressive by taking field sensitive information into
account.

llvm-svn: 20781
This commit is contained in:
Chris Lattner 2005-03-23 01:48:09 +00:00
parent 13417b5be3
commit e36d77b726
1 changed files with 18 additions and 8 deletions
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26
llvm/lib/Analysis/DataStructure/Steensgaard.cpp
View File

@ -192,21 +192,31 @@ AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
if (I != GSM.end() && I->second.getNode()) {
if (I != GSM.end() && !I->second.isNull() &&
I->second.getNode()->isComplete()) {
DSNodeHandle &V1H = I->second;
DSGraph::ScalarMapTy::iterator J=GSM.find(const_cast<Value*>(V2));
if (J != GSM.end() && J->second.getNode()) {
if (J != GSM.end() && !J->second.isNull() &&
J->second.getNode()->isComplete()) {
DSNodeHandle &V2H = J->second;
// If the two pointers point to different data structure graph nodes, they
// cannot alias!
if (V1H.getNode() != V2H.getNode()) // FIXME: Handle incompleteness!
if (V1H.getNode() != V2H.getNode())
return NoAlias;
// FIXME: If the two pointers point to the same node, and the offsets are
// different, and the LinkIndex vector doesn't alias the section, then the
// two pointers do not alias. We need access size information for the two
// accesses though!
//
// See if they point to different offsets... if so, we may be able to
// determine that they do not alias...
unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
if (O1 != O2) {
if (O2 < O1) { // Ensure that O1 <= O2
std::swap(V1, V2);
std::swap(O1, O2);
std::swap(V1Size, V2Size);
}
if (O1+V1Size <= O2)
return NoAlias;
}
}
}