[CFLAA] Move the graph builder out from CFLSteens. NFC.
Patch by Jia Chen.
Differential Revision: http://reviews.llvm.org/D22022
llvm-svn: 274958
diff --git a/llvm/lib/Analysis/CFLGraph.h b/llvm/lib/Analysis/CFLGraph.h
index cbc37f3..cfa5f54 100644
--- a/llvm/lib/Analysis/CFLGraph.h
+++ b/llvm/lib/Analysis/CFLGraph.h
@@ -17,6 +17,9 @@
#include "AliasAnalysisSummary.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/Instructions.h"
namespace llvm {
namespace cflaa {
@@ -144,6 +147,412 @@
bool empty() const { return NodeImpls.empty(); }
std::size_t size() const { return NodeImpls.size(); }
};
+
+///\brief A builder class used to create CFLGraph instance from a given function
+/// The CFL-AA that uses this builder must provide its own type as a template
+/// argument. This is necessary for interprocedural processing: CFLGraphBuilder
+/// needs a way of obtaining the summary of other functions when callinsts are
+/// encountered.
+/// As a result, we expect the said CFL-AA to expose a getAliasSummary() public
+/// member function that takes a Function& and returns the corresponding summary
+/// as a const AliasSummary*.
+template <typename CFLAA> class CFLGraphBuilder {
+ // Input of the builder
+ CFLAA &Analysis;
+ const TargetLibraryInfo &TLI;
+
+ // Output of the builder
+ CFLGraph Graph;
+ SmallVector<Value *, 4> ReturnedValues;
+
+ // Auxiliary structures used by the builder
+ SmallVector<InstantiatedRelation, 8> InstantiatedRelations;
+ SmallVector<InstantiatedAttr, 8> InstantiatedAttrs;
+
+ // Helper class
+ /// Gets the edges our graph should have, based on an Instruction*
+ class GetEdgesVisitor : public InstVisitor<GetEdgesVisitor, void> {
+ CFLAA &AA;
+ const TargetLibraryInfo &TLI;
+
+ CFLGraph &Graph;
+ SmallVectorImpl<Value *> &ReturnValues;
+ SmallVectorImpl<InstantiatedRelation> &InstantiatedRelations;
+ SmallVectorImpl<InstantiatedAttr> &InstantiatedAttrs;
+
+ static bool hasUsefulEdges(ConstantExpr *CE) {
+ // ConstantExpr doesn't have terminators, invokes, or fences, so only
+ // needs
+ // to check for compares.
+ return CE->getOpcode() != Instruction::ICmp &&
+ CE->getOpcode() != Instruction::FCmp;
+ }
+
+ // Returns possible functions called by CS into the given SmallVectorImpl.
+ // Returns true if targets found, false otherwise.
+ static bool getPossibleTargets(CallSite CS,
+ SmallVectorImpl<Function *> &Output) {
+ if (auto *Fn = CS.getCalledFunction()) {
+ Output.push_back(Fn);
+ return true;
+ }
+
+ // TODO: If the call is indirect, we might be able to enumerate all
+ // potential
+ // targets of the call and return them, rather than just failing.
+ return false;
+ }
+
+ void addNode(Value *Val) {
+ assert(Val != nullptr);
+ if (!Graph.addNode(Val))
+ return;
+
+ if (isa<GlobalValue>(Val)) {
+ Graph.addAttr(Val, getGlobalOrArgAttrFromValue(*Val));
+ // Currently we do not attempt to be smart on globals
+ InstantiatedAttrs.push_back(
+ InstantiatedAttr{InstantiatedValue{Val, 1}, getAttrUnknown()});
+ } else if (auto CExpr = dyn_cast<ConstantExpr>(Val))
+ if (hasUsefulEdges(CExpr))
+ visitConstantExpr(CExpr);
+ }
+
+ void addNodeWithAttr(Value *Val, AliasAttrs Attr) {
+ addNode(Val);
+ Graph.addAttr(Val, Attr);
+ }
+
+ void addEdge(Value *From, Value *To, EdgeType Type) {
+ assert(From != nullptr && To != nullptr);
+ if (!From->getType()->isPointerTy() || !To->getType()->isPointerTy())
+ return;
+ addNode(From);
+ if (To != From)
+ addNode(To);
+ Graph.addEdge(From, To, Type);
+ }
+
+ public:
+ GetEdgesVisitor(CFLGraphBuilder &Builder)
+ : AA(Builder.Analysis), TLI(Builder.TLI), Graph(Builder.Graph),
+ ReturnValues(Builder.ReturnedValues),
+ InstantiatedRelations(Builder.InstantiatedRelations),
+ InstantiatedAttrs(Builder.InstantiatedAttrs) {}
+
+ void visitInstruction(Instruction &) {
+ llvm_unreachable("Unsupported instruction encountered");
+ }
+
+ void visitReturnInst(ReturnInst &Inst) {
+ if (auto RetVal = Inst.getReturnValue()) {
+ if (RetVal->getType()->isPointerTy()) {
+ addNode(RetVal);
+ ReturnValues.push_back(RetVal);
+ }
+ }
+ }
+
+ void visitPtrToIntInst(PtrToIntInst &Inst) {
+ auto *Ptr = Inst.getOperand(0);
+ addNodeWithAttr(Ptr, getAttrEscaped());
+ }
+
+ void visitIntToPtrInst(IntToPtrInst &Inst) {
+ auto *Ptr = &Inst;
+ addNodeWithAttr(Ptr, getAttrUnknown());
+ }
+
+ void visitCastInst(CastInst &Inst) {
+ auto *Src = Inst.getOperand(0);
+ addEdge(Src, &Inst, EdgeType::Assign);
+ }
+
+ void visitBinaryOperator(BinaryOperator &Inst) {
+ auto *Op1 = Inst.getOperand(0);
+ auto *Op2 = Inst.getOperand(1);
+ addEdge(Op1, &Inst, EdgeType::Assign);
+ addEdge(Op2, &Inst, EdgeType::Assign);
+ }
+
+ void visitAtomicCmpXchgInst(AtomicCmpXchgInst &Inst) {
+ auto *Ptr = Inst.getPointerOperand();
+ auto *Val = Inst.getNewValOperand();
+ addEdge(Ptr, Val, EdgeType::Dereference);
+ }
+
+ void visitAtomicRMWInst(AtomicRMWInst &Inst) {
+ auto *Ptr = Inst.getPointerOperand();
+ auto *Val = Inst.getValOperand();
+ addEdge(Ptr, Val, EdgeType::Dereference);
+ }
+
+ void visitPHINode(PHINode &Inst) {
+ for (Value *Val : Inst.incoming_values())
+ addEdge(Val, &Inst, EdgeType::Assign);
+ }
+
+ void visitGetElementPtrInst(GetElementPtrInst &Inst) {
+ auto *Op = Inst.getPointerOperand();
+ addEdge(Op, &Inst, EdgeType::Assign);
+ }
+
+ void visitSelectInst(SelectInst &Inst) {
+ // Condition is not processed here (The actual statement producing
+ // the condition result is processed elsewhere). For select, the
+ // condition is evaluated, but not loaded, stored, or assigned
+ // simply as a result of being the condition of a select.
+
+ auto *TrueVal = Inst.getTrueValue();
+ auto *FalseVal = Inst.getFalseValue();
+ addEdge(TrueVal, &Inst, EdgeType::Assign);
+ addEdge(FalseVal, &Inst, EdgeType::Assign);
+ }
+
+ void visitAllocaInst(AllocaInst &Inst) { Graph.addNode(&Inst); }
+
+ void visitLoadInst(LoadInst &Inst) {
+ auto *Ptr = Inst.getPointerOperand();
+ auto *Val = &Inst;
+ addEdge(Val, Ptr, EdgeType::Reference);
+ }
+
+ void visitStoreInst(StoreInst &Inst) {
+ auto *Ptr = Inst.getPointerOperand();
+ auto *Val = Inst.getValueOperand();
+ addEdge(Ptr, Val, EdgeType::Dereference);
+ }
+
+ void visitVAArgInst(VAArgInst &Inst) {
+ // We can't fully model va_arg here. For *Ptr = Inst.getOperand(0), it
+ // does
+ // two things:
+ // 1. Loads a value from *((T*)*Ptr).
+ // 2. Increments (stores to) *Ptr by some target-specific amount.
+ // For now, we'll handle this like a landingpad instruction (by placing
+ // the
+ // result in its own group, and having that group alias externals).
+ addNodeWithAttr(&Inst, getAttrUnknown());
+ }
+
+ static bool isFunctionExternal(Function *Fn) {
+ return !Fn->hasExactDefinition();
+ }
+
+ bool tryInterproceduralAnalysis(CallSite CS,
+ const SmallVectorImpl<Function *> &Fns) {
+ assert(Fns.size() > 0);
+
+ if (CS.arg_size() > MaxSupportedArgsInSummary)
+ return false;
+
+ // Exit early if we'll fail anyway
+ for (auto *Fn : Fns) {
+ if (isFunctionExternal(Fn) || Fn->isVarArg())
+ return false;
+ // Fail if the caller does not provide enough arguments
+ assert(Fn->arg_size() <= CS.arg_size());
+ if (!AA.getAliasSummary(*Fn))
+ return false;
+ }
+
+ for (auto *Fn : Fns) {
+ auto Summary = AA.getAliasSummary(*Fn);
+ assert(Summary != nullptr);
+
+ auto &RetParamRelations = Summary->RetParamRelations;
+ for (auto &Relation : RetParamRelations) {
+ auto IRelation = instantiateExternalRelation(Relation, CS);
+ if (IRelation.hasValue())
+ InstantiatedRelations.push_back(*IRelation);
+ }
+
+ auto &RetParamAttributes = Summary->RetParamAttributes;
+ for (auto &Attribute : RetParamAttributes) {
+ auto IAttr = instantiateExternalAttribute(Attribute, CS);
+ if (IAttr.hasValue())
+ InstantiatedAttrs.push_back(*IAttr);
+ }
+ }
+
+ return true;
+ }
+
+ void visitCallSite(CallSite CS) {
+ auto Inst = CS.getInstruction();
+
+ // Make sure all arguments and return value are added to the graph first
+ for (Value *V : CS.args())
+ addNode(V);
+ if (Inst->getType()->isPointerTy())
+ addNode(Inst);
+
+ // Check if Inst is a call to a library function that
+ // allocates/deallocates
+ // on the heap. Those kinds of functions do not introduce any aliases.
+ // TODO: address other common library functions such as realloc(),
+ // strdup(),
+ // etc.
+ if (isMallocLikeFn(Inst, &TLI) || isCallocLikeFn(Inst, &TLI) ||
+ isFreeCall(Inst, &TLI))
+ return;
+
+ // TODO: Add support for noalias args/all the other fun function
+ // attributes
+ // that we can tack on.
+ SmallVector<Function *, 4> Targets;
+ if (getPossibleTargets(CS, Targets))
+ if (tryInterproceduralAnalysis(CS, Targets))
+ return;
+
+ // Because the function is opaque, we need to note that anything
+ // could have happened to the arguments (unless the function is marked
+ // readonly or readnone), and that the result could alias just about
+ // anything, too (unless the result is marked noalias).
+ if (!CS.onlyReadsMemory())
+ for (Value *V : CS.args()) {
+ if (V->getType()->isPointerTy()) {
+ // The argument itself escapes.
+ addNodeWithAttr(V, getAttrEscaped());
+ // The fate of argument memory is unknown. Note that since
+ // AliasAttrs
+ // is transitive with respect to dereference, we only need to
+ // specify
+ // it for the first-level memory.
+ InstantiatedAttrs.push_back(
+ InstantiatedAttr{InstantiatedValue{V, 1}, getAttrUnknown()});
+ }
+ }
+
+ if (Inst->getType()->isPointerTy()) {
+ auto *Fn = CS.getCalledFunction();
+ if (Fn == nullptr || !Fn->doesNotAlias(0))
+ // No need to call addNodeWithAttr() since we've added Inst at the
+ // beginning of this function and we know it is not a global.
+ Graph.addAttr(Inst, getAttrUnknown());
+ }
+ }
+
+ /// Because vectors/aggregates are immutable and unaddressable, there's
+ /// nothing we can do to coax a value out of them, other than calling
+ /// Extract{Element,Value}. We can effectively treat them as pointers to
+ /// arbitrary memory locations we can store in and load from.
+ void visitExtractElementInst(ExtractElementInst &Inst) {
+ auto *Ptr = Inst.getVectorOperand();
+ auto *Val = &Inst;
+ addEdge(Val, Ptr, EdgeType::Reference);
+ }
+
+ void visitInsertElementInst(InsertElementInst &Inst) {
+ auto *Vec = Inst.getOperand(0);
+ auto *Val = Inst.getOperand(1);
+ addEdge(Vec, &Inst, EdgeType::Assign);
+ addEdge(&Inst, Val, EdgeType::Dereference);
+ }
+
+ void visitLandingPadInst(LandingPadInst &Inst) {
+ // Exceptions come from "nowhere", from our analysis' perspective.
+ // So we place the instruction its own group, noting that said group may
+ // alias externals
+ addNodeWithAttr(&Inst, getAttrUnknown());
+ }
+
+ void visitInsertValueInst(InsertValueInst &Inst) {
+ auto *Agg = Inst.getOperand(0);
+ auto *Val = Inst.getOperand(1);
+ addEdge(Agg, &Inst, EdgeType::Assign);
+ addEdge(&Inst, Val, EdgeType::Dereference);
+ }
+
+ void visitExtractValueInst(ExtractValueInst &Inst) {
+ auto *Ptr = Inst.getAggregateOperand();
+ addEdge(&Inst, Ptr, EdgeType::Reference);
+ }
+
+ void visitShuffleVectorInst(ShuffleVectorInst &Inst) {
+ auto *From1 = Inst.getOperand(0);
+ auto *From2 = Inst.getOperand(1);
+ addEdge(From1, &Inst, EdgeType::Assign);
+ addEdge(From2, &Inst, EdgeType::Assign);
+ }
+
+ void visitConstantExpr(ConstantExpr *CE) {
+ switch (CE->getOpcode()) {
+ default:
+ llvm_unreachable("Unknown instruction type encountered!");
+// Build the switch statement using the Instruction.def file.
+#define HANDLE_INST(NUM, OPCODE, CLASS) \
+ case Instruction::OPCODE: \
+ this->visit##OPCODE(*(CLASS *)CE); \
+ break;
+#include "llvm/IR/Instruction.def"
+ }
+ }
+ };
+
+ // Helper functions
+
+ // Determines whether or not we an instruction is useless to us (e.g.
+ // FenceInst)
+ static bool hasUsefulEdges(Instruction *Inst) {
+ bool IsNonInvokeRetTerminator = isa<TerminatorInst>(Inst) &&
+ !isa<InvokeInst>(Inst) &&
+ !isa<ReturnInst>(Inst);
+ return !isa<CmpInst>(Inst) && !isa<FenceInst>(Inst) &&
+ !IsNonInvokeRetTerminator;
+ }
+
+ void addArgumentToGraph(Argument &Arg) {
+ if (Arg.getType()->isPointerTy()) {
+ Graph.addNode(&Arg);
+ Graph.addAttr(&Arg, getGlobalOrArgAttrFromValue(Arg));
+ // Pointees of a formal parameter is known to the caller
+ InstantiatedAttrs.push_back(
+ InstantiatedAttr{InstantiatedValue{&Arg, 1}, getAttrCaller()});
+ }
+ }
+
+ // Given an Instruction, this will add it to the graph, along with any
+ // Instructions that are potentially only available from said Instruction
+ // For example, given the following line:
+ // %0 = load i16* getelementptr ([1 x i16]* @a, 0, 0), align 2
+ // addInstructionToGraph would add both the `load` and `getelementptr`
+ // instructions to the graph appropriately.
+ void addInstructionToGraph(Instruction &Inst) {
+ if (!hasUsefulEdges(&Inst))
+ return;
+
+ GetEdgesVisitor(*this).visit(Inst);
+ }
+
+ // Builds the graph needed for constructing the StratifiedSets for the given
+ // function
+ void buildGraphFrom(Function &Fn) {
+ for (auto &Bb : Fn.getBasicBlockList())
+ for (auto &Inst : Bb.getInstList())
+ addInstructionToGraph(Inst);
+
+ for (auto &Arg : Fn.args())
+ addArgumentToGraph(Arg);
+ }
+
+public:
+ CFLGraphBuilder(CFLAA &Analysis, const TargetLibraryInfo &TLI, Function &Fn)
+ : Analysis(Analysis), TLI(TLI) {
+ buildGraphFrom(Fn);
+ }
+
+ const CFLGraph &getCFLGraph() const { return Graph; }
+ const SmallVector<Value *, 4> &getReturnValues() const {
+ return ReturnedValues;
+ }
+ const SmallVector<InstantiatedRelation, 8> &getInstantiatedRelations() const {
+ return InstantiatedRelations;
+ }
+ const SmallVector<InstantiatedAttr, 8> &getInstantiatedAttrs() const {
+ return InstantiatedAttrs;
+ }
+};
}
}