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//===-- Arena.h -------------------------------*- C++ -------------------*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H
#define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H
#include "clang/Analysis/FlowSensitive/Formula.h"
#include "clang/Analysis/FlowSensitive/StorageLocation.h"
#include "clang/Analysis/FlowSensitive/Value.h"
#include "llvm/ADT/StringRef.h"
#include <vector>
namespace clang::dataflow {
/// The Arena owns the objects that model data within an analysis.
/// For example, `Value`, `StorageLocation`, `Atom`, and `Formula`.
class Arena {
public:
Arena()
: True(Formula::create(Alloc, Formula::Literal, {}, 1)),
False(Formula::create(Alloc, Formula::Literal, {}, 0)) {}
Arena(const Arena &) = delete;
Arena &operator=(const Arena &) = delete;
/// Creates a `T` (some subclass of `StorageLocation`), forwarding `args` to
/// the constructor, and returns a reference to it.
///
/// The `Arena` takes ownership of the created object. The object will be
/// destroyed when the `Arena` is destroyed.
template <typename T, typename... Args>
std::enable_if_t<std::is_base_of<StorageLocation, T>::value, T &>
create(Args &&...args) {
// Note: If allocation of individual `StorageLocation`s turns out to be
// costly, consider creating specializations of `create<T>` for commonly
// used `StorageLocation` subclasses and make them use a `BumpPtrAllocator`.
return *cast<T>(
Locs.emplace_back(std::make_unique<T>(std::forward<Args>(args)...))
.get());
}
/// Creates a `T` (some subclass of `Value`), forwarding `args` to the
/// constructor, and returns a reference to it.
///
/// The `Arena` takes ownership of the created object. The object will be
/// destroyed when the `Arena` is destroyed.
template <typename T, typename... Args>
std::enable_if_t<std::is_base_of<Value, T>::value, T &>
create(Args &&...args) {
// Note: If allocation of individual `Value`s turns out to be costly,
// consider creating specializations of `create<T>` for commonly used
// `Value` subclasses and make them use a `BumpPtrAllocator`.
return *cast<T>(
Vals.emplace_back(std::make_unique<T>(std::forward<Args>(args)...))
.get());
}
/// Creates a BoolValue wrapping a particular formula.
///
/// Passing in the same formula will result in the same BoolValue.
/// FIXME: Interning BoolValues but not other Values is inconsistent.
/// Decide whether we want Value interning or not.
BoolValue &makeBoolValue(const Formula &);
/// Creates a fresh atom and wraps in in an AtomicBoolValue.
/// FIXME: For now, identical-address AtomicBoolValue <=> identical atom.
/// Stop relying on pointer identity and remove this guarantee.
AtomicBoolValue &makeAtomValue() {
return cast<AtomicBoolValue>(makeBoolValue(makeAtomRef(makeAtom())));
}
/// Creates a fresh Top boolean value.
TopBoolValue &makeTopValue() {
// No need for deduplicating: there's no way to create aliasing Tops.
return create<TopBoolValue>(makeAtomRef(makeAtom()));
}
/// Returns a symbolic integer value that models an integer literal equal to
/// `Value`. These literals are the same every time.
/// Integer literals are not typed; the type is determined by the `Expr` that
/// an integer literal is associated with.
IntegerValue &makeIntLiteral(llvm::APInt Value);
// Factories for boolean formulas.
// Formulas are interned: passing the same arguments return the same result.
// For commutative operations like And/Or, interning ignores order.
// Simplifications are applied: makeOr(X, X) => X, etc.
/// Returns a formula for the conjunction of `LHS` and `RHS`.
const Formula &makeAnd(const Formula &LHS, const Formula &RHS);
/// Returns a formula for the disjunction of `LHS` and `RHS`.
const Formula &makeOr(const Formula &LHS, const Formula &RHS);
/// Returns a formula for the negation of `Val`.
const Formula &makeNot(const Formula &Val);
/// Returns a formula for `LHS => RHS`.
const Formula &makeImplies(const Formula &LHS, const Formula &RHS);
/// Returns a formula for `LHS <=> RHS`.
const Formula &makeEquals(const Formula &LHS, const Formula &RHS);
/// Returns a formula for the variable A.
const Formula &makeAtomRef(Atom A);
/// Returns a formula for a literal true/false.
const Formula &makeLiteral(bool Value) { return Value ? True : False; }
// Parses a formula from its textual representation.
// This may refer to atoms that were not produced by makeAtom() yet!
llvm::Expected<const Formula &> parseFormula(llvm::StringRef);
/// Returns a new atomic boolean variable, distinct from any other.
Atom makeAtom() { return static_cast<Atom>(NextAtom++); };
/// Creates a fresh flow condition and returns a token that identifies it. The
/// token can be used to perform various operations on the flow condition such
/// as adding constraints to it, forking it, joining it with another flow
/// condition, or checking implications.
Atom makeFlowConditionToken() { return makeAtom(); }
private:
llvm::BumpPtrAllocator Alloc;
// Storage for the state of a program.
std::vector<std::unique_ptr<StorageLocation>> Locs;
std::vector<std::unique_ptr<Value>> Vals;
// Indices that are used to avoid recreating the same integer literals and
// composite boolean values.
llvm::DenseMap<llvm::APInt, IntegerValue *> IntegerLiterals;
using FormulaPair = std::pair<const Formula *, const Formula *>;
llvm::DenseMap<FormulaPair, const Formula *> Ands;
llvm::DenseMap<FormulaPair, const Formula *> Ors;
llvm::DenseMap<const Formula *, const Formula *> Nots;
llvm::DenseMap<FormulaPair, const Formula *> Implies;
llvm::DenseMap<FormulaPair, const Formula *> Equals;
llvm::DenseMap<Atom, const Formula *> AtomRefs;
llvm::DenseMap<const Formula *, BoolValue *> FormulaValues;
unsigned NextAtom = 0;
const Formula &True, &False;
};
} // namespace clang::dataflow
#endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H
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