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llvm-mirror/lib/Analysis/DataStructure/Steensgaard.cpp
Reid Spencer 2567610703 For PR387:
Close out this long standing bug by removing the remaining overloaded
virtual functions in LLVM. The -Woverloaded-virtual option is now turned on.

llvm-svn: 29934
2006-08-28 01:02:49 +00:00

276 lines
9.9 KiB
C++

//===- Steensgaard.cpp - Context Insensitive 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 data structure graphs to implement a simple context
// insensitive alias analysis. It does this by computing the local analysis
// graphs for all of the functions, then merging them together into a single big
// graph without cloning.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/DataStructure/DataStructure.h"
#include "llvm/Analysis/DataStructure/DSGraph.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Module.h"
#include "llvm/Support/Debug.h"
#include <iostream>
using namespace llvm;
namespace {
class Steens : public ModulePass, public AliasAnalysis {
DSGraph *ResultGraph;
EquivalenceClasses<GlobalValue*> GlobalECs; // Always empty
public:
Steens() : ResultGraph(0) {}
~Steens() {
releaseMyMemory();
assert(ResultGraph == 0 && "releaseMemory not called?");
}
//------------------------------------------------
// Implement the Pass API
//
// run - Build up the result graph, representing the pointer graph for the
// program.
//
bool runOnModule(Module &M);
virtual void releaseMyMemory() { delete ResultGraph; ResultGraph = 0; }
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AliasAnalysis::getAnalysisUsage(AU);
AU.setPreservesAll(); // Does not transform code...
AU.addRequired<LocalDataStructures>(); // Uses local dsgraph
}
// print - Implement the Pass::print method...
void print(std::ostream &O, const Module *M) const {
assert(ResultGraph && "Result graph has not yet been computed!");
ResultGraph->writeGraphToFile(O, "steensgaards");
}
//------------------------------------------------
// Implement the AliasAnalysis API
//
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
private:
void ResolveFunctionCall(Function *F, const DSCallSite &Call,
DSNodeHandle &RetVal);
};
// Register the pass...
RegisterPass<Steens> X("steens-aa",
"Steensgaard's alias analysis (DSGraph based)");
// Register as an implementation of AliasAnalysis
RegisterAnalysisGroup<AliasAnalysis> Y(X);
}
ModulePass *llvm::createSteensgaardPass() { return new Steens(); }
/// ResolveFunctionCall - Resolve the actual arguments of a call to function F
/// with the specified call site descriptor. This function links the arguments
/// and the return value for the call site context-insensitively.
///
void Steens::ResolveFunctionCall(Function *F, const DSCallSite &Call,
DSNodeHandle &RetVal) {
assert(ResultGraph != 0 && "Result graph not allocated!");
DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();
// Handle the return value of the function...
if (Call.getRetVal().getNode() && RetVal.getNode())
RetVal.mergeWith(Call.getRetVal());
// Loop over all pointer arguments, resolving them to their provided pointers
unsigned PtrArgIdx = 0;
for (Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
if (I != ValMap.end()) // If its a pointer argument...
I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
}
}
/// run - Build up the result graph, representing the pointer graph for the
/// program.
///
bool Steens::runOnModule(Module &M) {
InitializeAliasAnalysis(this);
assert(ResultGraph == 0 && "Result graph already allocated!");
LocalDataStructures &LDS = getAnalysis<LocalDataStructures>();
// Create a new, empty, graph...
ResultGraph = new DSGraph(GlobalECs, getTargetData());
ResultGraph->spliceFrom(LDS.getGlobalsGraph());
// Loop over the rest of the module, merging graphs for non-external functions
// into this graph.
//
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (!I->isExternal())
ResultGraph->spliceFrom(LDS.getDSGraph(*I));
ResultGraph->removeTriviallyDeadNodes();
// FIXME: Must recalculate and use the Incomplete markers!!
// Now that we have all of the graphs inlined, we can go about eliminating
// call nodes...
//
std::list<DSCallSite> &Calls = ResultGraph->getAuxFunctionCalls();
assert(Calls.empty() && "Aux call list is already in use??");
// Start with a copy of the original call sites.
Calls = ResultGraph->getFunctionCalls();
for (std::list<DSCallSite>::iterator CI = Calls.begin(), E = Calls.end();
CI != E;) {
DSCallSite &CurCall = *CI++;
// Loop over the called functions, eliminating as many as possible...
std::vector<Function*> CallTargets;
if (CurCall.isDirectCall())
CallTargets.push_back(CurCall.getCalleeFunc());
else
CurCall.getCalleeNode()->addFullFunctionList(CallTargets);
for (unsigned c = 0; c != CallTargets.size(); ) {
// If we can eliminate this function call, do so!
Function *F = CallTargets[c];
if (!F->isExternal()) {
ResolveFunctionCall(F, CurCall, ResultGraph->getReturnNodes()[F]);
CallTargets[c] = CallTargets.back();
CallTargets.pop_back();
} else
++c; // Cannot eliminate this call, skip over it...
}
if (CallTargets.empty()) { // Eliminated all calls?
std::list<DSCallSite>::iterator I = CI;
Calls.erase(--I); // Remove entry
}
}
// Remove our knowledge of what the return values of the functions are, except
// for functions that are externally visible from this module (e.g. main). We
// keep these functions so that their arguments are marked incomplete.
for (DSGraph::ReturnNodesTy::iterator I =
ResultGraph->getReturnNodes().begin(),
E = ResultGraph->getReturnNodes().end(); I != E; )
if (I->first->hasInternalLinkage())
ResultGraph->getReturnNodes().erase(I++);
else
++I;
// Update the "incomplete" markers on the nodes, ignoring unknownness due to
// incoming arguments...
ResultGraph->maskIncompleteMarkers();
ResultGraph->markIncompleteNodes(DSGraph::IgnoreGlobals |
DSGraph::MarkFormalArgs);
// Remove any nodes that are dead after all of the merging we have done...
// FIXME: We should be able to disable the globals graph for steens!
//ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);
DEBUG(print(std::cerr, &M));
return false;
}
AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
assert(ResultGraph && "Result graph has not been computed yet!");
DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
DSGraph::ScalarMapTy::iterator J = GSM.find(const_cast<Value*>(V2));
if (I != GSM.end() && !I->second.isNull() &&
J != GSM.end() && !J->second.isNull()) {
DSNodeHandle &V1H = I->second;
DSNodeHandle &V2H = J->second;
// If at least one of the nodes is complete, we can say something about
// this. If one is complete and the other isn't, then they are obviously
// different nodes. If they are both complete, we can't say anything
// useful.
if (I->second.getNode()->isComplete() ||
J->second.getNode()->isComplete()) {
// If the two pointers point to different data structure graph nodes, they
// cannot alias!
if (V1H.getNode() != V2H.getNode())
return NoAlias;
// See if they point to different offsets... if so, we may be able to
// determine that they do not alias...
unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
if (O1 != O2) {
if (O2 < O1) { // Ensure that O1 <= O2
std::swap(V1, V2);
std::swap(O1, O2);
std::swap(V1Size, V2Size);
}
if (O1+V1Size <= O2)
return NoAlias;
}
}
}
// If we cannot determine alias properties based on our graph, fall back on
// some other AA implementation.
//
return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
}
AliasAnalysis::ModRefResult
Steens::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
AliasAnalysis::ModRefResult Result = ModRef;
// Find the node in question.
DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
DSGraph::ScalarMapTy::iterator I = GSM.find(P);
if (I != GSM.end() && !I->second.isNull()) {
DSNode *N = I->second.getNode();
if (N->isComplete()) {
// If this is a direct call to an external function, and if the pointer
// points to a complete node, the external function cannot modify or read
// the value (we know it's not passed out of the program!).
if (Function *F = CS.getCalledFunction())
if (F->isExternal())
return NoModRef;
// Otherwise, if the node is complete, but it is only M or R, return this.
// This can be useful for globals that should be marked const but are not.
if (!N->isModified())
Result = (ModRefResult)(Result & ~Mod);
if (!N->isRead())
Result = (ModRefResult)(Result & ~Ref);
}
}
return (ModRefResult)(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
}
AliasAnalysis::ModRefResult
Steens::getModRefInfo(CallSite CS1, CallSite CS2)
{
return AliasAnalysis::getModRefInfo(CS1,CS2);
}