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Teach steens-aa two things about mod/ref information:
1. If memory never escapes the program, it cannot be mod/ref'd by external functions. 2. If memory is global never mod/ref'd in the program, it cannot be mod/ref'd by any call. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20867 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -62,10 +62,11 @@ namespace {
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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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ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
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private:
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void ResolveFunctionCall(Function *F, const DSCallSite &Call,
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DSNodeHandle &RetVal);
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@ -183,7 +184,6 @@ bool Steens::runOnModule(Module &M) {
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return false;
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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 Steens::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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assert(ResultGraph && "Result graph has not been computed yet!");
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@ -224,3 +224,33 @@ AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
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//
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return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
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}
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AliasAnalysis::ModRefResult
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Steens::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
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AliasAnalysis::ModRefResult Result = ModRef;
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// Find the node in question.
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DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
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DSGraph::ScalarMapTy::iterator I = GSM.find(P);
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if (I != GSM.end() && !I->second.isNull()) {
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DSNode *N = I->second.getNode();
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if (N->isComplete()) {
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// If this is a direct call to an external function, and if the pointer
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// points to a complete node, the external function cannot modify or read
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// the value (we know it's not passed out of the program!).
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if (Function *F = CS.getCalledFunction())
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if (F->isExternal())
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return NoModRef;
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// Otherwise, if the node is complete, but it is only M or R, return this.
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// This can be useful for globals that should be marked const but are not.
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if (!N->isModified())
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Result = (ModRefResult)(Result & ~Mod);
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if (!N->isRead())
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Result = (ModRefResult)(Result & ~Ref);
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}
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}
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return (ModRefResult)(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
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}
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