CFLAliasAnalysis.cpp [plain text]
#include "llvm/Analysis/CFLAliasAnalysis.h"
#include "StratifiedSets.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <memory>
#include <tuple>
using namespace llvm;
#define DEBUG_TYPE "cfl-aa"
CFLAAResult::CFLAAResult() : AAResultBase() {}
CFLAAResult::CFLAAResult(CFLAAResult &&Arg) : AAResultBase(std::move(Arg)) {}
struct CFLAAResult::FunctionInfo {
StratifiedSets<Value *> Sets;
SmallVector<Value *, 4> ReturnedValues;
FunctionInfo(StratifiedSets<Value *> &&S, SmallVector<Value *, 4> &&RV)
: Sets(std::move(S)), ReturnedValues(std::move(RV)) {}
};
static Optional<Function *> parentFunctionOfValue(Value *);
template <typename Inst>
static bool getPossibleTargets(Inst *, SmallVectorImpl<Function *> &);
static Optional<Value *> getTargetValue(Instruction *);
static bool hasUsefulEdges(Instruction *);
const StratifiedIndex StratifiedLink::SetSentinel =
std::numeric_limits<StratifiedIndex>::max();
namespace {
typedef unsigned StratifiedAttr;
LLVM_CONSTEXPR unsigned MaxStratifiedAttrIndex = NumStratifiedAttrs;
LLVM_CONSTEXPR unsigned AttrAllIndex = 0;
LLVM_CONSTEXPR unsigned AttrGlobalIndex = 1;
LLVM_CONSTEXPR unsigned AttrUnknownIndex = 2;
LLVM_CONSTEXPR unsigned AttrFirstArgIndex = 3;
LLVM_CONSTEXPR unsigned AttrLastArgIndex = MaxStratifiedAttrIndex;
LLVM_CONSTEXPR unsigned AttrMaxNumArgs = AttrLastArgIndex - AttrFirstArgIndex;
LLVM_CONSTEXPR StratifiedAttr AttrNone = 0;
LLVM_CONSTEXPR StratifiedAttr AttrUnknown = 1 << AttrUnknownIndex;
LLVM_CONSTEXPR StratifiedAttr AttrAll = ~AttrNone;
enum class Level { Same, Above, Below };
enum class EdgeType {
Assign,
Dereference,
Reference
};
struct Edge {
Value *From;
Value *To;
EdgeType Weight;
StratifiedAttrs AdditionalAttrs;
Edge(Value *From, Value *To, EdgeType W, StratifiedAttrs A)
: From(From), To(To), Weight(W), AdditionalAttrs(A) {}
};
class GetEdgesVisitor : public InstVisitor<GetEdgesVisitor, void> {
CFLAAResult &AA;
SmallVectorImpl<Edge> &Output;
public:
GetEdgesVisitor(CFLAAResult &AA, SmallVectorImpl<Edge> &Output)
: AA(AA), Output(Output) {}
void visitInstruction(Instruction &) {
llvm_unreachable("Unsupported instruction encountered");
}
void visitPtrToIntInst(PtrToIntInst &Inst) {
auto *Ptr = Inst.getOperand(0);
Output.push_back(Edge(Ptr, Ptr, EdgeType::Assign, AttrUnknown));
}
void visitIntToPtrInst(IntToPtrInst &Inst) {
auto *Ptr = &Inst;
Output.push_back(Edge(Ptr, Ptr, EdgeType::Assign, AttrUnknown));
}
void visitCastInst(CastInst &Inst) {
Output.push_back(
Edge(&Inst, Inst.getOperand(0), EdgeType::Assign, AttrNone));
}
void visitBinaryOperator(BinaryOperator &Inst) {
auto *Op1 = Inst.getOperand(0);
auto *Op2 = Inst.getOperand(1);
Output.push_back(Edge(&Inst, Op1, EdgeType::Assign, AttrNone));
Output.push_back(Edge(&Inst, Op2, EdgeType::Assign, AttrNone));
}
void visitAtomicCmpXchgInst(AtomicCmpXchgInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getNewValOperand();
Output.push_back(Edge(Ptr, Val, EdgeType::Dereference, AttrNone));
}
void visitAtomicRMWInst(AtomicRMWInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValOperand();
Output.push_back(Edge(Ptr, Val, EdgeType::Dereference, AttrNone));
}
void visitPHINode(PHINode &Inst) {
for (Value *Val : Inst.incoming_values()) {
Output.push_back(Edge(&Inst, Val, EdgeType::Assign, AttrNone));
}
}
void visitGetElementPtrInst(GetElementPtrInst &Inst) {
auto *Op = Inst.getPointerOperand();
Output.push_back(Edge(&Inst, Op, EdgeType::Assign, AttrNone));
for (auto I = Inst.idx_begin(), E = Inst.idx_end(); I != E; ++I)
Output.push_back(Edge(&Inst, *I, EdgeType::Assign, AttrNone));
}
void visitSelectInst(SelectInst &Inst) {
auto *TrueVal = Inst.getTrueValue();
Output.push_back(Edge(&Inst, TrueVal, EdgeType::Assign, AttrNone));
auto *FalseVal = Inst.getFalseValue();
Output.push_back(Edge(&Inst, FalseVal, EdgeType::Assign, AttrNone));
}
void visitAllocaInst(AllocaInst &) {}
void visitLoadInst(LoadInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = &Inst;
Output.push_back(Edge(Val, Ptr, EdgeType::Reference, AttrNone));
}
void visitStoreInst(StoreInst &Inst) {
auto *Ptr = Inst.getPointerOperand();
auto *Val = Inst.getValueOperand();
Output.push_back(Edge(Ptr, Val, EdgeType::Dereference, AttrNone));
}
void visitVAArgInst(VAArgInst &Inst) {
auto *Val = &Inst;
Output.push_back(Edge(Val, Val, EdgeType::Assign, AttrAll));
}
static bool isFunctionExternal(Function *Fn) {
return Fn->isDeclaration() || !Fn->hasLocalLinkage();
}
static Optional<Level> getIndexRelation(const StratifiedSets<Value *> &Sets,
StratifiedIndex Index1,
StratifiedIndex Index2) {
if (Index1 == Index2)
return Level::Same;
const auto *Current = &Sets.getLink(Index1);
while (Current->hasBelow()) {
if (Current->Below == Index2)
return Level::Below;
Current = &Sets.getLink(Current->Below);
}
Current = &Sets.getLink(Index1);
while (Current->hasAbove()) {
if (Current->Above == Index2)
return Level::Above;
Current = &Sets.getLink(Current->Above);
}
return NoneType();
}
bool
tryInterproceduralAnalysis(const SmallVectorImpl<Function *> &Fns,
Value *FuncValue,
const iterator_range<User::op_iterator> &Args) {
const unsigned ExpectedMaxArgs = 8;
const unsigned MaxSupportedArgs = 50;
assert(Fns.size() > 0);
if (std::distance(Args.begin(), Args.end()) > (int)MaxSupportedArgs)
return false;
for (auto *Fn : Fns) {
if (isFunctionExternal(Fn) || Fn->isVarArg())
return false;
auto &MaybeInfo = AA.ensureCached(Fn);
if (!MaybeInfo.hasValue())
return false;
}
SmallVector<Value *, ExpectedMaxArgs> Arguments(Args.begin(), Args.end());
SmallVector<StratifiedInfo, ExpectedMaxArgs> Parameters;
for (auto *Fn : Fns) {
auto &Info = *AA.ensureCached(Fn);
auto &Sets = Info.Sets;
auto &RetVals = Info.ReturnedValues;
Parameters.clear();
for (auto &Param : Fn->args()) {
auto MaybeInfo = Sets.find(&Param);
if (!MaybeInfo.hasValue())
return false;
Parameters.push_back(*MaybeInfo);
}
for (unsigned I = 0, E = Parameters.size(); I != E; ++I) {
auto &ParamInfo = Parameters[I];
auto &ArgVal = Arguments[I];
bool AddEdge = false;
StratifiedAttrs Externals;
for (unsigned X = 0, XE = RetVals.size(); X != XE; ++X) {
auto MaybeInfo = Sets.find(RetVals[X]);
if (!MaybeInfo.hasValue())
return false;
auto &RetInfo = *MaybeInfo;
auto RetAttrs = Sets.getLink(RetInfo.Index).Attrs;
auto ParamAttrs = Sets.getLink(ParamInfo.Index).Attrs;
auto MaybeRelation =
getIndexRelation(Sets, ParamInfo.Index, RetInfo.Index);
if (MaybeRelation.hasValue()) {
AddEdge = true;
Externals |= RetAttrs | ParamAttrs;
}
}
if (AddEdge)
Output.push_back(Edge(FuncValue, ArgVal, EdgeType::Assign,
StratifiedAttrs().flip()));
}
if (Parameters.size() != Arguments.size())
return false;
for (unsigned I = 0, E = Arguments.size(); I != E; ++I) {
auto &MainVal = Arguments[I];
auto &MainInfo = Parameters[I];
auto &MainAttrs = Sets.getLink(MainInfo.Index).Attrs;
for (unsigned X = I + 1; X != E; ++X) {
auto &SubInfo = Parameters[X];
auto &SubVal = Arguments[X];
auto &SubAttrs = Sets.getLink(SubInfo.Index).Attrs;
auto MaybeRelation =
getIndexRelation(Sets, MainInfo.Index, SubInfo.Index);
if (!MaybeRelation.hasValue())
continue;
auto NewAttrs = SubAttrs | MainAttrs;
Output.push_back(Edge(MainVal, SubVal, EdgeType::Assign, NewAttrs));
}
}
}
return true;
}
template <typename InstT> void visitCallLikeInst(InstT &Inst) {
SmallVector<Function *, 4> Targets;
if (getPossibleTargets(&Inst, Targets)) {
if (tryInterproceduralAnalysis(Targets, &Inst, Inst.arg_operands()))
return;
Output.clear();
}
for (Value *V : Inst.arg_operands())
Output.push_back(Edge(&Inst, V, EdgeType::Assign, AttrAll));
if (Inst.getNumArgOperands() == 0 &&
Inst.getType() != Type::getVoidTy(Inst.getContext()))
Output.push_back(Edge(&Inst, &Inst, EdgeType::Assign, AttrAll));
}
void visitCallInst(CallInst &Inst) { visitCallLikeInst(Inst); }
void visitInvokeInst(InvokeInst &Inst) { visitCallLikeInst(Inst); }
void visitExtractElementInst(ExtractElementInst &Inst) {
auto *Ptr = Inst.getVectorOperand();
auto *Val = &Inst;
Output.push_back(Edge(Val, Ptr, EdgeType::Reference, AttrNone));
}
void visitInsertElementInst(InsertElementInst &Inst) {
auto *Vec = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
Output.push_back(Edge(&Inst, Vec, EdgeType::Assign, AttrNone));
Output.push_back(Edge(&Inst, Val, EdgeType::Dereference, AttrNone));
}
void visitLandingPadInst(LandingPadInst &Inst) {
Output.push_back(Edge(&Inst, &Inst, EdgeType::Assign, AttrAll));
}
void visitInsertValueInst(InsertValueInst &Inst) {
auto *Agg = Inst.getOperand(0);
auto *Val = Inst.getOperand(1);
Output.push_back(Edge(&Inst, Agg, EdgeType::Assign, AttrNone));
Output.push_back(Edge(&Inst, Val, EdgeType::Dereference, AttrNone));
}
void visitExtractValueInst(ExtractValueInst &Inst) {
auto *Ptr = Inst.getAggregateOperand();
Output.push_back(Edge(&Inst, Ptr, EdgeType::Reference, AttrNone));
}
void visitShuffleVectorInst(ShuffleVectorInst &Inst) {
auto *From1 = Inst.getOperand(0);
auto *From2 = Inst.getOperand(1);
Output.push_back(Edge(&Inst, From1, EdgeType::Assign, AttrNone));
Output.push_back(Edge(&Inst, From2, EdgeType::Assign, AttrNone));
}
void visitConstantExpr(ConstantExpr *CE) {
switch (CE->getOpcode()) {
default:
llvm_unreachable("Unknown instruction type encountered!");
#define HANDLE_INST(NUM, OPCODE, CLASS) \
case Instruction::OPCODE: \
visit##OPCODE(*(CLASS *)CE); \
break;
#include "llvm/IR/Instruction.def"
}
}
};
class GetTargetValueVisitor
: public InstVisitor<GetTargetValueVisitor, Value *> {
public:
Value *visitInstruction(Instruction &Inst) { return &Inst; }
Value *visitStoreInst(StoreInst &Inst) { return Inst.getPointerOperand(); }
Value *visitAtomicCmpXchgInst(AtomicCmpXchgInst &Inst) {
return Inst.getPointerOperand();
}
Value *visitAtomicRMWInst(AtomicRMWInst &Inst) {
return Inst.getPointerOperand();
}
Value *visitInsertElementInst(InsertElementInst &Inst) {
return Inst.getOperand(0);
}
Value *visitInsertValueInst(InsertValueInst &Inst) {
return Inst.getAggregateOperand();
}
};
template <typename EdgeTypeT> class WeightedBidirectionalGraph {
public:
typedef std::size_t Node;
private:
const static Node StartNode = Node(0);
struct Edge {
EdgeTypeT Weight;
Node Other;
Edge(const EdgeTypeT &W, const Node &N) : Weight(W), Other(N) {}
bool operator==(const Edge &E) const {
return Weight == E.Weight && Other == E.Other;
}
bool operator!=(const Edge &E) const { return !operator==(E); }
};
struct NodeImpl {
std::vector<Edge> Edges;
};
std::vector<NodeImpl> NodeImpls;
bool inbounds(Node NodeIndex) const { return NodeIndex < NodeImpls.size(); }
const NodeImpl &getNode(Node N) const { return NodeImpls[N]; }
NodeImpl &getNode(Node N) { return NodeImpls[N]; }
public:
struct EdgeIterator : public std::iterator<std::forward_iterator_tag,
std::tuple<EdgeTypeT, Node *>> {
EdgeIterator(const typename std::vector<Edge>::const_iterator &Iter)
: Current(Iter) {}
EdgeIterator(NodeImpl &Impl) : Current(Impl.begin()) {}
EdgeIterator &operator++() {
++Current;
return *this;
}
EdgeIterator operator++(int) {
EdgeIterator Copy(Current);
operator++();
return Copy;
}
std::tuple<EdgeTypeT, Node> &operator*() {
Store = std::make_tuple(Current->Weight, Current->Other);
return Store;
}
bool operator==(const EdgeIterator &Other) const {
return Current == Other.Current;
}
bool operator!=(const EdgeIterator &Other) const {
return !operator==(Other);
}
private:
typename std::vector<Edge>::const_iterator Current;
std::tuple<EdgeTypeT, Node> Store;
};
struct EdgeIterable {
EdgeIterable(const std::vector<Edge> &Edges)
: BeginIter(Edges.begin()), EndIter(Edges.end()) {}
EdgeIterator begin() { return EdgeIterator(BeginIter); }
EdgeIterator end() { return EdgeIterator(EndIter); }
private:
typename std::vector<Edge>::const_iterator BeginIter;
typename std::vector<Edge>::const_iterator EndIter;
};
WeightedBidirectionalGraph() {}
WeightedBidirectionalGraph(WeightedBidirectionalGraph<EdgeTypeT> &&Other)
: NodeImpls(std::move(Other.NodeImpls)) {}
WeightedBidirectionalGraph<EdgeTypeT> &
operator=(WeightedBidirectionalGraph<EdgeTypeT> &&Other) {
NodeImpls = std::move(Other.NodeImpls);
return *this;
}
Node addNode() {
auto Index = NodeImpls.size();
auto NewNode = Node(Index);
NodeImpls.push_back(NodeImpl());
return NewNode;
}
void addEdge(Node From, Node To, const EdgeTypeT &Weight,
const EdgeTypeT &ReverseWeight) {
assert(inbounds(From));
assert(inbounds(To));
auto &FromNode = getNode(From);
auto &ToNode = getNode(To);
FromNode.Edges.push_back(Edge(Weight, To));
ToNode.Edges.push_back(Edge(ReverseWeight, From));
}
EdgeIterable edgesFor(const Node &N) const {
const auto &Node = getNode(N);
return EdgeIterable(Node.Edges);
}
bool empty() const { return NodeImpls.empty(); }
std::size_t size() const { return NodeImpls.size(); }
Node getEntryNode() {
assert(inbounds(StartNode));
return StartNode;
}
};
typedef WeightedBidirectionalGraph<std::pair<EdgeType, StratifiedAttrs>> GraphT;
typedef DenseMap<Value *, GraphT::Node> NodeMapT;
}
static StratifiedAttr argNumberToAttrIndex(StratifiedAttr);
static Optional<StratifiedAttr> valueToAttrIndex(Value *Val);
static EdgeType flipWeight(EdgeType);
static void argsToEdges(CFLAAResult &, Instruction *, SmallVectorImpl<Edge> &);
static void argsToEdges(CFLAAResult &, ConstantExpr *, SmallVectorImpl<Edge> &);
static Level directionOfEdgeType(EdgeType);
static void buildGraphFrom(CFLAAResult &, Function *,
SmallVectorImpl<Value *> &, NodeMapT &, GraphT &);
static void constexprToEdges(CFLAAResult &, ConstantExpr &,
SmallVectorImpl<Edge> &);
static void addInstructionToGraph(CFLAAResult &, Instruction &,
SmallVectorImpl<Value *> &, NodeMapT &,
GraphT &);
static bool canSkipAddingToSets(Value *Val);
static Optional<Function *> parentFunctionOfValue(Value *Val) {
if (auto *Inst = dyn_cast<Instruction>(Val)) {
auto *Bb = Inst->getParent();
return Bb->getParent();
}
if (auto *Arg = dyn_cast<Argument>(Val))
return Arg->getParent();
return NoneType();
}
template <typename Inst>
static bool getPossibleTargets(Inst *Call,
SmallVectorImpl<Function *> &Output) {
if (auto *Fn = Call->getCalledFunction()) {
Output.push_back(Fn);
return true;
}
return false;
}
static Optional<Value *> getTargetValue(Instruction *Inst) {
GetTargetValueVisitor V;
return V.visit(Inst);
}
static bool hasUsefulEdges(Instruction *Inst) {
bool IsNonInvokeTerminator =
isa<TerminatorInst>(Inst) && !isa<InvokeInst>(Inst);
return !isa<CmpInst>(Inst) && !isa<FenceInst>(Inst) && !IsNonInvokeTerminator;
}
static bool hasUsefulEdges(ConstantExpr *CE) {
return CE->getOpcode() != Instruction::ICmp &&
CE->getOpcode() != Instruction::FCmp;
}
static Optional<StratifiedAttr> valueToAttrIndex(Value *Val) {
if (isa<GlobalValue>(Val))
return AttrGlobalIndex;
if (auto *Arg = dyn_cast<Argument>(Val))
if (!Arg->hasNoAliasAttr() && Arg->getType()->isPointerTy())
return argNumberToAttrIndex(Arg->getArgNo());
return NoneType();
}
static StratifiedAttr argNumberToAttrIndex(unsigned ArgNum) {
if (ArgNum >= AttrMaxNumArgs)
return AttrAllIndex;
return ArgNum + AttrFirstArgIndex;
}
static EdgeType flipWeight(EdgeType Initial) {
switch (Initial) {
case EdgeType::Assign:
return EdgeType::Assign;
case EdgeType::Dereference:
return EdgeType::Reference;
case EdgeType::Reference:
return EdgeType::Dereference;
}
llvm_unreachable("Incomplete coverage of EdgeType enum");
}
static void argsToEdges(CFLAAResult &Analysis, Instruction *Inst,
SmallVectorImpl<Edge> &Output) {
assert(hasUsefulEdges(Inst) &&
"Expected instructions to have 'useful' edges");
GetEdgesVisitor v(Analysis, Output);
v.visit(Inst);
}
static void argsToEdges(CFLAAResult &Analysis, ConstantExpr *CE,
SmallVectorImpl<Edge> &Output) {
assert(hasUsefulEdges(CE) && "Expected constant expr to have 'useful' edges");
GetEdgesVisitor v(Analysis, Output);
v.visitConstantExpr(CE);
}
static Level directionOfEdgeType(EdgeType Weight) {
switch (Weight) {
case EdgeType::Reference:
return Level::Above;
case EdgeType::Dereference:
return Level::Below;
case EdgeType::Assign:
return Level::Same;
}
llvm_unreachable("Incomplete switch coverage");
}
static void constexprToEdges(CFLAAResult &Analysis,
ConstantExpr &CExprToCollapse,
SmallVectorImpl<Edge> &Results) {
SmallVector<ConstantExpr *, 4> Worklist;
Worklist.push_back(&CExprToCollapse);
SmallVector<Edge, 8> ConstexprEdges;
SmallPtrSet<ConstantExpr *, 4> Visited;
while (!Worklist.empty()) {
auto *CExpr = Worklist.pop_back_val();
if (!hasUsefulEdges(CExpr))
continue;
ConstexprEdges.clear();
argsToEdges(Analysis, CExpr, ConstexprEdges);
for (auto &Edge : ConstexprEdges) {
if (auto *Nested = dyn_cast<ConstantExpr>(Edge.From))
if (Visited.insert(Nested).second)
Worklist.push_back(Nested);
if (auto *Nested = dyn_cast<ConstantExpr>(Edge.To))
if (Visited.insert(Nested).second)
Worklist.push_back(Nested);
}
Results.append(ConstexprEdges.begin(), ConstexprEdges.end());
}
}
static void addInstructionToGraph(CFLAAResult &Analysis, Instruction &Inst,
SmallVectorImpl<Value *> &ReturnedValues,
NodeMapT &Map, GraphT &Graph) {
const auto findOrInsertNode = [&Map, &Graph](Value *Val) {
auto Pair = Map.insert(std::make_pair(Val, GraphT::Node()));
auto &Iter = Pair.first;
if (Pair.second) {
auto NewNode = Graph.addNode();
Iter->second = NewNode;
}
return Iter->second;
};
if (isa<ReturnInst>(&Inst))
ReturnedValues.push_back(&Inst);
if (!hasUsefulEdges(&Inst))
return;
SmallVector<Edge, 8> Edges;
argsToEdges(Analysis, &Inst, Edges);
if (Edges.empty()) {
auto MaybeVal = getTargetValue(&Inst);
assert(MaybeVal.hasValue());
auto *Target = *MaybeVal;
findOrInsertNode(Target);
return;
}
const auto addEdgeToGraph = [&Graph, &findOrInsertNode](const Edge &E) {
auto To = findOrInsertNode(E.To);
auto From = findOrInsertNode(E.From);
auto FlippedWeight = flipWeight(E.Weight);
auto Attrs = E.AdditionalAttrs;
Graph.addEdge(From, To, std::make_pair(E.Weight, Attrs),
std::make_pair(FlippedWeight, Attrs));
};
SmallVector<ConstantExpr *, 4> ConstantExprs;
for (const Edge &E : Edges) {
addEdgeToGraph(E);
if (auto *Constexpr = dyn_cast<ConstantExpr>(E.To))
ConstantExprs.push_back(Constexpr);
if (auto *Constexpr = dyn_cast<ConstantExpr>(E.From))
ConstantExprs.push_back(Constexpr);
}
for (ConstantExpr *CE : ConstantExprs) {
Edges.clear();
constexprToEdges(Analysis, *CE, Edges);
std::for_each(Edges.begin(), Edges.end(), addEdgeToGraph);
}
}
static void buildGraphFrom(CFLAAResult &Analysis, Function *Fn,
SmallVectorImpl<Value *> &ReturnedValues,
NodeMapT &Map, GraphT &Graph) {
for (auto &Bb : Fn->getBasicBlockList())
for (auto &Inst : Bb.getInstList())
addInstructionToGraph(Analysis, Inst, ReturnedValues, Map, Graph);
}
static bool canSkipAddingToSets(Value *Val) {
if (isa<Constant>(Val)) {
bool Container = isa<ConstantVector>(Val) || isa<ConstantArray>(Val) ||
isa<ConstantStruct>(Val);
bool CanStoreMutableData =
isa<GlobalValue>(Val) || isa<ConstantExpr>(Val) || Container;
return !CanStoreMutableData;
}
return false;
}
CFLAAResult::FunctionInfo CFLAAResult::buildSetsFrom(Function *Fn) {
NodeMapT Map;
GraphT Graph;
SmallVector<Value *, 4> ReturnedValues;
buildGraphFrom(*this, Fn, ReturnedValues, Map, Graph);
DenseMap<GraphT::Node, Value *> NodeValueMap;
NodeValueMap.reserve(Map.size());
for (const auto &Pair : Map)
NodeValueMap.insert(std::make_pair(Pair.second, Pair.first));
const auto findValueOrDie = [&NodeValueMap](GraphT::Node Node) {
auto ValIter = NodeValueMap.find(Node);
assert(ValIter != NodeValueMap.end());
return ValIter->second;
};
StratifiedSetsBuilder<Value *> Builder;
SmallVector<GraphT::Node, 16> Worklist;
for (auto &Pair : Map) {
Worklist.clear();
auto *Value = Pair.first;
Builder.add(Value);
auto InitialNode = Pair.second;
Worklist.push_back(InitialNode);
while (!Worklist.empty()) {
auto Node = Worklist.pop_back_val();
auto *CurValue = findValueOrDie(Node);
if (canSkipAddingToSets(CurValue))
continue;
Optional<StratifiedAttr> MaybeCurIndex = valueToAttrIndex(CurValue);
if (MaybeCurIndex)
Builder.noteAttributes(CurValue, *MaybeCurIndex);
for (const auto &EdgeTuple : Graph.edgesFor(Node)) {
auto Weight = std::get<0>(EdgeTuple);
auto Label = Weight.first;
auto &OtherNode = std::get<1>(EdgeTuple);
auto *OtherValue = findValueOrDie(OtherNode);
if (canSkipAddingToSets(OtherValue))
continue;
bool Added;
switch (directionOfEdgeType(Label)) {
case Level::Above:
Added = Builder.addAbove(CurValue, OtherValue);
break;
case Level::Below:
Added = Builder.addBelow(CurValue, OtherValue);
break;
case Level::Same:
Added = Builder.addWith(CurValue, OtherValue);
break;
}
auto Aliasing = Weight.second;
if (MaybeCurIndex)
Aliasing.set(*MaybeCurIndex);
if (auto MaybeOtherIndex = valueToAttrIndex(OtherValue))
Aliasing.set(*MaybeOtherIndex);
Builder.noteAttributes(CurValue, Aliasing);
Builder.noteAttributes(OtherValue, Aliasing);
if (Added)
Worklist.push_back(OtherNode);
}
}
}
for (auto &Arg : Fn->args()) {
if (!Builder.add(&Arg))
continue;
auto Attrs = valueToAttrIndex(&Arg);
if (Attrs.hasValue())
Builder.noteAttributes(&Arg, *Attrs);
}
return FunctionInfo(Builder.build(), std::move(ReturnedValues));
}
void CFLAAResult::scan(Function *Fn) {
auto InsertPair = Cache.insert(std::make_pair(Fn, Optional<FunctionInfo>()));
(void)InsertPair;
assert(InsertPair.second &&
"Trying to scan a function that has already been cached");
FunctionInfo Info(buildSetsFrom(Fn));
Cache[Fn] = std::move(Info);
Handles.push_front(FunctionHandle(Fn, this));
}
void CFLAAResult::evict(Function *Fn) { Cache.erase(Fn); }
const Optional<CFLAAResult::FunctionInfo> &
CFLAAResult::ensureCached(Function *Fn) {
auto Iter = Cache.find(Fn);
if (Iter == Cache.end()) {
scan(Fn);
Iter = Cache.find(Fn);
assert(Iter != Cache.end());
assert(Iter->second.hasValue());
}
return Iter->second;
}
AliasResult CFLAAResult::query(const MemoryLocation &LocA,
const MemoryLocation &LocB) {
auto *ValA = const_cast<Value *>(LocA.Ptr);
auto *ValB = const_cast<Value *>(LocB.Ptr);
Function *Fn = nullptr;
auto MaybeFnA = parentFunctionOfValue(ValA);
auto MaybeFnB = parentFunctionOfValue(ValB);
if (!MaybeFnA.hasValue() && !MaybeFnB.hasValue()) {
DEBUG(dbgs() << "CFLAA: could not extract parent function information.\n");
return MayAlias;
}
if (MaybeFnA.hasValue()) {
Fn = *MaybeFnA;
assert((!MaybeFnB.hasValue() || *MaybeFnB == *MaybeFnA) &&
"Interprocedural queries not supported");
} else {
Fn = *MaybeFnB;
}
assert(Fn != nullptr);
auto &MaybeInfo = ensureCached(Fn);
assert(MaybeInfo.hasValue());
auto &Sets = MaybeInfo->Sets;
auto MaybeA = Sets.find(ValA);
if (!MaybeA.hasValue())
return MayAlias;
auto MaybeB = Sets.find(ValB);
if (!MaybeB.hasValue())
return MayAlias;
auto SetA = *MaybeA;
auto SetB = *MaybeB;
auto AttrsA = Sets.getLink(SetA.Index).Attrs;
auto AttrsB = Sets.getLink(SetB.Index).Attrs;
if (AttrsA.any() && AttrsB.any())
return MayAlias;
if (SetA.Index == SetB.Index)
return MayAlias;
return NoAlias;
}
CFLAAResult CFLAA::run(Function &F, AnalysisManager<Function> *AM) {
return CFLAAResult();
}
char CFLAA::PassID;
char CFLAAWrapperPass::ID = 0;
INITIALIZE_PASS(CFLAAWrapperPass, "cfl-aa", "CFL-Based Alias Analysis", false,
true)
ImmutablePass *llvm::createCFLAAWrapperPass() { return new CFLAAWrapperPass(); }
CFLAAWrapperPass::CFLAAWrapperPass() : ImmutablePass(ID) {
initializeCFLAAWrapperPassPass(*PassRegistry::getPassRegistry());
}
bool CFLAAWrapperPass::doInitialization(Module &M) {
Result.reset(new CFLAAResult());
return false;
}
bool CFLAAWrapperPass::doFinalization(Module &M) {
Result.reset();
return false;
}
void CFLAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}