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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6945 91177308-0d34-0410-b5e6-96231b3b80d8
124 lines
4.4 KiB
C++
124 lines
4.4 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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InitializeAliasAnalysis(this);
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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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AliasAnalysis::getAnalysisUsage(AU);
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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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AliasResult alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size);
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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::AliasResult DSAA::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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if (V1 == V2) return MustAlias;
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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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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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DSNode *N1 = I->second.getNode(), *N2 = J->second.getNode();
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unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
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// We can only make a judgement of one of the nodes is complete...
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if (N1->isComplete() || N2->isComplete()) {
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if (N1 != N2)
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return NoAlias; // Completely different nodes.
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// Both point to the same node and same offset, and there is only one
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// physical memory object represented in the node, return must alias.
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//if (O1 == O2 && !N1->isMultiObject())
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// return MustAlias; // Exactly the same object & offset
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// See if they point to different offsets... if so, we may be able to
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// determine that they do not alias...
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if (O1 != O2) {
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if (O2 < O1) { // Ensure that O1 <= O2
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std::swap(V1, V2);
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std::swap(O1, O2);
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std::swap(V1Size, V2Size);
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}
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// FIXME: This is not correct because we do not handle array
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// indexing correctly with this check!
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//if (O1+V1Size <= O2) return NoAlias;
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}
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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, V1Size, V2, V2Size);
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}
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