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118 lines
4.0 KiB
C++
118 lines
4.0 KiB
C++
//===- DataStructureAA.cpp - Data Structure Based Alias Analysis ----------===//
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//
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// This pass uses the top-down data structure graphs to implement a simple
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// context sensitive alias analysis.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/DataStructure.h"
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#include "llvm/Analysis/DSGraph.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Module.h"
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namespace {
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class DSAA : public Pass, public AliasAnalysis {
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TDDataStructures *TD;
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public:
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DSAA() : TD(0) {}
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//------------------------------------------------
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// Implement the Pass API
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//
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// run - Build up the result graph, representing the pointer graph for the
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// program.
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//
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bool run(Module &M) {
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TD = &getAnalysis<TDDataStructures>();
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return false;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll(); // Does not transform code...
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AU.addRequired<TDDataStructures>(); // Uses TD Datastructures
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AU.addRequired<AliasAnalysis>(); // Chains to another AA impl...
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}
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//------------------------------------------------
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// Implement the AliasAnalysis API
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//
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// alias - This is the only method here that does anything interesting...
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Result alias(const Value *V1, const Value *V2);
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/// canCallModify - Not implemented yet: FIXME
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///
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Result canCallModify(const CallInst &CI, const Value *Ptr) {
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return MayAlias;
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}
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/// canInvokeModify - Not implemented yet: FIXME
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///
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Result canInvokeModify(const InvokeInst &I, const Value *Ptr) {
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return MayAlias;
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}
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};
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// Register the pass...
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RegisterOpt<DSAA> X("ds-aa", "Data Structure Graph Based Alias Analysis");
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// Register as an implementation of AliasAnalysis
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RegisterAnalysisGroup<AliasAnalysis, DSAA> Y;
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}
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// getValueFunction - return the function containing the specified value if
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// available, or null otherwise.
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//
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static const Function *getValueFunction(const Value *V) {
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if (const Instruction *I = dyn_cast<Instruction>(V))
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return I->getParent()->getParent();
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else if (const Argument *A = dyn_cast<Argument>(V))
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return A->getParent();
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else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
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return BB->getParent();
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return 0;
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}
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// alias - This is the only method here that does anything interesting...
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AliasAnalysis::Result DSAA::alias(const Value *V1, const Value *V2) {
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const Function *F1 = getValueFunction(V1);
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const Function *F2 = getValueFunction(V2);
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assert((!F1 || !F2 || F1 == F2) && "Alias query for 2 different functions?");
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// FIXME: This can return must alias if querying a DSNode for a global value
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// where the node has only the G composition bit set, and only one entry in
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// the globals list...
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if (F2) F1 = F2;
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if (F1) {
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// Get the graph for a function...
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DSGraph &G = TD->getDSGraph(*F1);
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hash_map<Value*, DSNodeHandle> &GSM = G.getScalarMap();
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hash_map<Value*, DSNodeHandle>::iterator I = GSM.find((Value*)V1);
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if (I != GSM.end()) {
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assert(I->second.getNode() && "Scalar map points to null node?");
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hash_map<Value*, DSNodeHandle>::iterator J = GSM.find((Value*)V2);
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if (J != GSM.end()) {
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assert(J->second.getNode() && "Scalar map points to null node?");
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if (I->second.getNode() != J->second.getNode()) {
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// Return noalias if one of the nodes is complete...
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if ((~I->second.getNode()->NodeType | ~J->second.getNode()->NodeType)
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& DSNode::Incomplete)
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return NoAlias;
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// both are incomplete, they may alias...
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} else {
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// Both point to the same node, see if they point to different
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// offsets... FIXME: This needs to know the size of the alias query
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if (I->second.getOffset() != J->second.getOffset())
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return NoAlias;
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}
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}
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}
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}
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// FIXME: we could improve on this by checking the globals graph for aliased
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// global queries...
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return getAnalysis<AliasAnalysis>().alias(V1, V2);
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}
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