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authorChris Lattner <sabre@nondot.org>2003-02-03 22:50:46 +0000
committerChris Lattner <sabre@nondot.org>2003-02-03 22:50:46 +0000
commit8105cfbed0b4e51b6d7d62ad3e84885e27451cf3 (patch)
tree55ba83e6e0f8ed0dbdf10ff855002da27fe2029d /lib/Analysis/DataStructure/DataStructureAA.cpp
parent1cdfd83d627ae7138f85f0333475b665b50a944e (diff)
Initial implementation of ds-aa
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5484 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis/DataStructure/DataStructureAA.cpp')
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1 files changed, 128 insertions, 0 deletions
diff --git a/lib/Analysis/DataStructure/DataStructureAA.cpp b/lib/Analysis/DataStructure/DataStructureAA.cpp
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+//===- DataStructureAA.cpp - Data Structure Based Alias Analysis ----------===//
+//
+// 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 "Support/Statistic.h"
+
+namespace {
+ Statistic<> NumNoAlias ("ds-aa", "Number of 'no alias' replies");
+ Statistic<> NumMayAlias ("ds-aa", "Number of 'may alias' replies");
+};
+
+namespace {
+ class DSAA : public Pass, public AliasAnalysis {
+ TDDataStructures *TD;
+ public:
+ DSAA() : TD(0) {}
+
+ //------------------------------------------------
+ // Implement the Pass API
+ //
+
+ // run - Build up the result graph, representing the pointer graph for the
+ // program.
+ //
+ bool run(Module &M) {
+ TD = &getAnalysis<TDDataStructures>();
+ 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...
+ }
+
+ //------------------------------------------------
+ // 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;
+ }
+ };
+
+ // Register the pass...
+ RegisterOpt<DSAA> X("ds-aa", "Data Structure Graph Based Alias Analysis");
+
+ // Register as an implementation of AliasAnalysis
+ RegisterAnalysisGroup<AliasAnalysis, DSAA> Y;
+}
+
+// getValueFunction - return the function containing the specified value if
+// available, or null otherwise.
+//
+static const Function *getValueFunction(const Value *V) {
+ if (const Instruction *I = dyn_cast<Instruction>(V))
+ return I->getParent()->getParent();
+ else if (const Argument *A = dyn_cast<Argument>(V))
+ return A->getParent();
+ else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
+ return BB->getParent();
+ return 0;
+}
+
+// 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?");
+
+
+ // 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) {
+ ++NumNoAlias;
+ 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()) {
+ ++NumNoAlias;
+ return NoAlias;
+ }
+ }
+ }
+ }
+ }
+
+ // FIXME: we could improve on this by checking the globals graph for aliased
+ // global queries...
+ ++NumMayAlias;
+ return getAnalysis<AliasAnalysis>().alias(V1, V2);
+}