llvm-6502/lib/Analysis/DataStructure/DataStructureAA.cpp
Misha Brukman 2b37d7cf28 Remove trailing whitespace
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21416 91177308-0d34-0410-b5e6-96231b3b80d8
2005-04-21 21:13:18 +00:00

301 lines
11 KiB
C++

//===- DataStructureAA.cpp - Data Structure Based 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 top-down data structure graphs to implement a simple
// context sensitive alias analysis.
//
//===----------------------------------------------------------------------===//
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/DataStructure/DataStructure.h"
#include "llvm/Analysis/DataStructure/DSGraph.h"
using namespace llvm;
namespace {
class DSAA : public ModulePass, public AliasAnalysis {
TDDataStructures *TD;
BUDataStructures *BU;
// These members are used to cache mod/ref information to make us return
// results faster, particularly for aa-eval. On the first request of
// mod/ref information for a particular call site, we compute and store the
// calculated nodemap for the call site. Any time DSA info is updated we
// free this information, and when we move onto a new call site, this
// information is also freed.
CallSite MapCS;
std::multimap<DSNode*, const DSNode*> CallerCalleeMap;
public:
DSAA() : TD(0) {}
~DSAA() {
InvalidateCache();
}
void InvalidateCache() {
MapCS = CallSite();
CallerCalleeMap.clear();
}
//------------------------------------------------
// Implement the Pass API
//
// run - Build up the result graph, representing the pointer graph for the
// program.
//
bool runOnModule(Module &M) {
InitializeAliasAnalysis(this);
TD = &getAnalysis<TDDataStructures>();
BU = &getAnalysis<BUDataStructures>();
return false;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AliasAnalysis::getAnalysisUsage(AU);
AU.setPreservesAll(); // Does not transform code
AU.addRequiredTransitive<TDDataStructures>(); // Uses TD Datastructures
AU.addRequiredTransitive<BUDataStructures>(); // Uses BU Datastructures
}
//------------------------------------------------
// Implement the AliasAnalysis API
//
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
return AliasAnalysis::getModRefInfo(CS1,CS2);
}
virtual void deleteValue(Value *V) {
InvalidateCache();
BU->deleteValue(V);
TD->deleteValue(V);
}
virtual void copyValue(Value *From, Value *To) {
if (From == To) return;
InvalidateCache();
BU->copyValue(From, To);
TD->copyValue(From, To);
}
private:
DSGraph *getGraphForValue(const Value *V);
};
// Register the pass...
RegisterOpt<DSAA> X("ds-aa", "Data Structure Graph Based Alias Analysis");
// Register as an implementation of AliasAnalysis
RegisterAnalysisGroup<AliasAnalysis, DSAA> Y;
}
ModulePass *llvm::createDSAAPass() { return new DSAA(); }
// getGraphForValue - Return the DSGraph to use for queries about the specified
// value...
//
DSGraph *DSAA::getGraphForValue(const Value *V) {
if (const Instruction *I = dyn_cast<Instruction>(V))
return &TD->getDSGraph(*I->getParent()->getParent());
else if (const Argument *A = dyn_cast<Argument>(V))
return &TD->getDSGraph(*A->getParent());
else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
return &TD->getDSGraph(*BB->getParent());
return 0;
}
AliasAnalysis::AliasResult DSAA::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
if (V1 == V2) return MustAlias;
DSGraph *G1 = getGraphForValue(V1);
DSGraph *G2 = getGraphForValue(V2);
assert((!G1 || !G2 || G1 == G2) && "Alias query for 2 different functions?");
// Get the graph to use...
DSGraph &G = *(G1 ? G1 : (G2 ? G2 : &TD->getGlobalsGraph()));
const DSGraph::ScalarMapTy &GSM = G.getScalarMap();
DSGraph::ScalarMapTy::const_iterator I = GSM.find((Value*)V1);
if (I == GSM.end()) return NoAlias;
DSGraph::ScalarMapTy::const_iterator J = GSM.find((Value*)V2);
if (J == GSM.end()) return NoAlias;
DSNode *N1 = I->second.getNode(), *N2 = J->second.getNode();
unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
if (N1 == 0 || N2 == 0)
// Can't tell whether anything aliases null.
return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
// We can only make a judgment if one of the nodes is complete.
if (N1->isComplete() || N2->isComplete()) {
if (N1 != N2)
return NoAlias; // Completely different nodes.
// See if they point to different offsets... if so, we may be able to
// determine that they do not alias...
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;
}
}
// FIXME: we could improve on this by checking the globals graph for aliased
// global queries...
return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
}
/// getModRefInfo - does a callsite modify or reference a value?
///
AliasAnalysis::ModRefResult
DSAA::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
DSNode *N = 0;
// First step, check our cache.
if (CS.getInstruction() == MapCS.getInstruction()) {
{
const Function *Caller = CS.getInstruction()->getParent()->getParent();
DSGraph &CallerTDGraph = TD->getDSGraph(*Caller);
// Figure out which node in the TD graph this pointer corresponds to.
DSScalarMap &CallerSM = CallerTDGraph.getScalarMap();
DSScalarMap::iterator NI = CallerSM.find(P);
if (NI == CallerSM.end()) {
InvalidateCache();
return DSAA::getModRefInfo(CS, P, Size);
}
N = NI->second.getNode();
}
HaveMappingInfo:
assert(N && "Null pointer in scalar map??");
typedef std::multimap<DSNode*, const DSNode*>::iterator NodeMapIt;
std::pair<NodeMapIt, NodeMapIt> Range = CallerCalleeMap.equal_range(N);
// Loop over all of the nodes in the callee that correspond to "N", keeping
// track of aggregate mod/ref info.
bool NeverReads = true, NeverWrites = true;
for (; Range.first != Range.second; ++Range.first) {
if (Range.first->second->isModified())
NeverWrites = false;
if (Range.first->second->isRead())
NeverReads = false;
if (NeverReads == false && NeverWrites == false)
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
ModRefResult Result = ModRef;
if (NeverWrites) // We proved it was not modified.
Result = ModRefResult(Result & ~Mod);
if (NeverReads) // We proved it was not read.
Result = ModRefResult(Result & ~Ref);
return ModRefResult(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
}
// Any cached info we have is for the wrong function.
InvalidateCache();
Function *F = CS.getCalledFunction();
if (!F) return AliasAnalysis::getModRefInfo(CS, P, Size);
if (F->isExternal()) {
// If we are calling an external function, and if this global doesn't escape
// the portion of the program we have analyzed, we can draw conclusions
// based on whether the global escapes the program.
Function *Caller = CS.getInstruction()->getParent()->getParent();
DSGraph *G = &TD->getDSGraph(*Caller);
DSScalarMap::iterator NI = G->getScalarMap().find(P);
if (NI == G->getScalarMap().end()) {
// If it wasn't in the local function graph, check the global graph. This
// can occur for globals who are locally reference but hoisted out to the
// globals graph despite that.
G = G->getGlobalsGraph();
NI = G->getScalarMap().find(P);
if (NI == G->getScalarMap().end())
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
// If we found a node and it's complete, it cannot be passed out to the
// called function.
if (NI->second.getNode()->isComplete())
return NoModRef;
return AliasAnalysis::getModRefInfo(CS, P, Size);
}
// Get the graphs for the callee and caller. Note that we want the BU graph
// for the callee because we don't want all caller's effects incorporated!
const Function *Caller = CS.getInstruction()->getParent()->getParent();
DSGraph &CallerTDGraph = TD->getDSGraph(*Caller);
DSGraph &CalleeBUGraph = BU->getDSGraph(*F);
// Figure out which node in the TD graph this pointer corresponds to.
DSScalarMap &CallerSM = CallerTDGraph.getScalarMap();
DSScalarMap::iterator NI = CallerSM.find(P);
if (NI == CallerSM.end()) {
ModRefResult Result = ModRef;
if (isa<ConstantPointerNull>(P) || isa<UndefValue>(P))
return NoModRef; // null is never modified :)
else {
assert(isa<GlobalVariable>(P) &&
cast<GlobalVariable>(P)->getType()->getElementType()->isFirstClassType() &&
"This isn't a global that DSA inconsiderately dropped "
"from the graph?");
DSGraph &GG = *CallerTDGraph.getGlobalsGraph();
DSScalarMap::iterator NI = GG.getScalarMap().find(P);
if (NI != GG.getScalarMap().end() && !NI->second.isNull()) {
// Otherwise, if the node is only M or R, return this. This can be
// useful for globals that should be marked const but are not.
DSNode *N = NI->second.getNode();
if (!N->isModified())
Result = (ModRefResult)(Result & ~Mod);
if (!N->isRead())
Result = (ModRefResult)(Result & ~Ref);
}
}
if (Result == NoModRef) return Result;
return ModRefResult(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
}
// Compute the mapping from nodes in the callee graph to the nodes in the
// caller graph for this call site.
DSGraph::NodeMapTy CalleeCallerMap;
DSCallSite DSCS = CallerTDGraph.getDSCallSiteForCallSite(CS);
CallerTDGraph.computeCalleeCallerMapping(DSCS, *F, CalleeBUGraph,
CalleeCallerMap);
// Remember the mapping and the call site for future queries.
MapCS = CS;
// Invert the mapping into CalleeCallerInvMap.
for (DSGraph::NodeMapTy::iterator I = CalleeCallerMap.begin(),
E = CalleeCallerMap.end(); I != E; ++I)
CallerCalleeMap.insert(std::make_pair(I->second.getNode(), I->first));
N = NI->second.getNode();
goto HaveMappingInfo;
}