//===- DataStructureAA.cpp - Data Structure Based Alias Analysis ----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// This pass uses the top-down data structure graphs to implement a simple
// context sensitive alias analysis.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/DataStructure.h"
-#include "llvm/Analysis/DSGraph.h"
-#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Module.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/DataStructure/DataStructure.h"
+#include "llvm/Analysis/DataStructure/DSGraph.h"
+using namespace llvm;
namespace {
class DSAA : public Pass, public AliasAnalysis {
TDDataStructures *TD;
+ BUDataStructures *BU;
public:
DSAA() : TD(0) {}
// program.
//
bool run(Module &M) {
+ InitializeAliasAnalysis(this);
TD = &getAnalysis<TDDataStructures>();
+ BU = &getAnalysis<BUDataStructures>();
return false;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll(); // Does not transform code...
- AU.addRequired<TDDataStructures>(); // Uses TD Datastructures
- AU.addRequired<AliasAnalysis>(); // Chains to another AA impl...
+ AliasAnalysis::getAnalysisUsage(AU);
+ AU.setPreservesAll(); // Does not transform code
+ AU.addRequiredTransitive<TDDataStructures>(); // Uses TD Datastructures
+ AU.addRequiredTransitive<BUDataStructures>(); // Uses BU Datastructures
}
//------------------------------------------------
// Implement the AliasAnalysis API
//
- // alias - This is the only method here that does anything interesting...
- Result alias(const Value *V1, const Value *V2);
-
- /// canCallModify - Not implemented yet: FIXME
- ///
- Result canCallModify(const CallInst &CI, const Value *Ptr) {
- return MayAlias;
- }
-
- /// canInvokeModify - Not implemented yet: FIXME
- ///
- Result canInvokeModify(const InvokeInst &I, const Value *Ptr) {
- return MayAlias;
- }
+ AliasResult alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+
+ void getMustAliases(Value *P, std::vector<Value*> &RetVals);
+
+ ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
+
+ private:
+ DSGraph *getGraphForValue(const Value *V);
};
// Register the pass...
RegisterAnalysisGroup<AliasAnalysis, DSAA> Y;
}
-// getValueFunction - return the function containing the specified value if
-// available, or null otherwise.
+// getGraphForValue - Return the DSGraph to use for queries about the specified
+// value...
//
-static const Function *getValueFunction(const Value *V) {
+DSGraph *DSAA::getGraphForValue(const Value *V) {
if (const Instruction *I = dyn_cast<Instruction>(V))
- return I->getParent()->getParent();
+ return &TD->getDSGraph(*I->getParent()->getParent());
else if (const Argument *A = dyn_cast<Argument>(V))
- return A->getParent();
+ return &TD->getDSGraph(*A->getParent());
else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
- return BB->getParent();
+ return &TD->getDSGraph(*BB->getParent());
return 0;
}
+// isSinglePhysicalObject - For now, the only case that we know that there is
+// only one memory object in the node is when there is a single global in the
+// node, and the only composition bit set is Global.
+//
+static bool isSinglePhysicalObject(DSNode *N) {
+ assert(N->isComplete() && "Can only tell if this is a complete object!");
+ return N->isGlobalNode() && N->getGlobals().size() == 1 &&
+ !N->isHeapNode() && !N->isAllocaNode() && !N->isUnknownNode();
+}
+
// alias - This is the only method here that does anything interesting...
-AliasAnalysis::Result DSAA::alias(const Value *V1, const Value *V2) {
- const Function *F1 = getValueFunction(V1);
- const Function *F2 = getValueFunction(V2);
- assert((!F1 || !F2 || F1 == F2) && "Alias query for 2 different functions?");
+AliasAnalysis::AliasResult DSAA::alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ if (V1 == V2) return MustAlias;
+
+ DSGraph *G1 = getGraphForValue(V1);
+ DSGraph *G2 = getGraphForValue(V2);
+ assert((!G1 || !G2 || G1 == G2) && "Alias query for 2 different functions?");
+ // Get the graph to use...
+ DSGraph &G = *(G1 ? G1 : (G2 ? G2 : &TD->getGlobalsGraph()));
+
+ const DSGraph::ScalarMapTy &GSM = G.getScalarMap();
+ DSGraph::ScalarMapTy::const_iterator I = GSM.find((Value*)V1);
+ if (I == GSM.end()) return NoAlias;
+
+ assert(I->second.getNode() && "Scalar map points to null node?");
+ DSGraph::ScalarMapTy::const_iterator J = GSM.find((Value*)V2);
+ if (J == GSM.end()) return NoAlias;
+
+ assert(J->second.getNode() && "Scalar map points to null node?");
- // 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...
- DSGraph &G = TD->getDSGraph(*F1);
- hash_map<Value*, DSNodeHandle> &GSM = G.getScalarMap();
- hash_map<Value*, DSNodeHandle>::iterator I = GSM.find((Value*)V1);
- if (I != GSM.end()) {
- assert(I->second.getNode() && "Scalar map points to null node?");
- 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 judgment of one of the nodes is complete...
+ if (N1->isComplete() || N2->isComplete()) {
+ if (N1 != N2)
+ return NoAlias; // Completely different nodes.
+
+#if 0 // This does not correctly handle arrays!
+ // Both point to the same node and same offset, and there is only one
+ // physical memory object represented in the node, return must alias.
+ //
+ // FIXME: This isn't correct because we do not handle array indexing
+ // correctly.
+
+ if (O1 == O2 && isSinglePhysicalObject(N1))
+ return MustAlias; // Exactly the same object & offset
+#endif
+
+ // 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;
}
}
// FIXME: we could improve on this by checking the globals graph for aliased
// global queries...
- return getAnalysis<AliasAnalysis>().alias(V1, V2);
+ return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
}
+
+/// getModRefInfo - does a callsite modify or reference a value?
+///
+AliasAnalysis::ModRefResult
+DSAA::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ Function *F = CS.getCalledFunction();
+ if (!F) return pointsToConstantMemory(P) ? Ref : ModRef;
+ if (F->isExternal()) return ModRef;
+
+ // Clone the function TD graph, clearing off Mod/Ref flags
+ const Function *csParent = CS.getInstruction()->getParent()->getParent();
+ DSGraph TDGraph(TD->getDSGraph(*csParent));
+ TDGraph.maskNodeTypes(0);
+
+ // Insert the callee's BU graph into the TD graph
+ const DSGraph &BUGraph = BU->getDSGraph(*F);
+ TDGraph.mergeInGraph(TDGraph.getDSCallSiteForCallSite(CS),
+ *F, BUGraph, 0);
+
+ // Report the flags that have been added
+ const DSNodeHandle &DSH = TDGraph.getNodeForValue(P);
+ if (const DSNode *N = DSH.getNode())
+ if (N->isModified())
+ return N->isRead() ? ModRef : Mod;
+ else
+ return N->isRead() ? Ref : NoModRef;
+ return NoModRef;
+}
+
+
+/// getMustAliases - If there are any pointers known that must alias this
+/// pointer, return them now. This allows alias-set based alias analyses to
+/// perform a form a value numbering (which is exposed by load-vn). If an alias
+/// analysis supports this, it should ADD any must aliased pointers to the
+/// specified vector.
+///
+void DSAA::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
+#if 0 // This does not correctly handle arrays!
+ // Currently the only must alias information we can provide is to say that
+ // something is equal to a global value. If we already have a global value,
+ // don't get worked up about it.
+ if (!isa<GlobalValue>(P)) {
+ DSGraph *G = getGraphForValue(P);
+ if (!G) G = &TD->getGlobalsGraph();
+
+ // The only must alias information we can currently determine occurs when
+ // the node for P is a global node with only one entry.
+ DSGraph::ScalarMapTy::const_iterator I = G->getScalarMap().find(P);
+ if (I != G->getScalarMap().end()) {
+ DSNode *N = I->second.getNode();
+ if (N->isComplete() && isSinglePhysicalObject(N))
+ RetVals.push_back(N->getGlobals()[0]);
+ }
+ }
+#endif
+ return AliasAnalysis::getMustAliases(P, RetVals);
+}
+
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