//===- CFG.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
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file provides various utilities for inspecting and working with the
/// control flow graph in LLVM IR. This includes generic facilities for
/// iterating successors and predecessors of basic blocks, the successors of
/// specific terminator instructions, etc. It also defines specializations of
/// GraphTraits that allow Function and BasicBlock graphs to be treated as
/// proper graphs for generic algorithms.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_CFG_H
#define LLVM_IR_CFG_H
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Value.h"
#include <cassert>
#include <cstddef>
#include <iterator>
namespace llvm {
class Instruction;
class Use;
//===----------------------------------------------------------------------===//
// BasicBlock pred_iterator definition
//===----------------------------------------------------------------------===//
template <class Ptr, class USE_iterator> // Predecessor Iterator
class PredIterator {
public:
using iterator_category = std::forward_iterator_tag;
using value_type = Ptr;
using difference_type = std::ptrdiff_t;
using pointer = Ptr *;
using reference = Ptr *;
protected:
using Self = PredIterator<Ptr, USE_iterator>;
USE_iterator It;
inline void advancePastNonTerminators() {
// Loop to ignore non-terminator uses (for example BlockAddresses).
while (!It.atEnd()) {
if (auto *Inst = dyn_cast<Instruction>(*It))
if (Inst->isTerminator())
break;
++It;
}
}
public:
PredIterator() = default;
explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
advancePastNonTerminators();
}
inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}
inline bool operator==(const Self& x) const { return It == x.It; }
inline bool operator!=(const Self& x) const { return !operator==(x); }
inline reference operator*() const {
assert(!It.atEnd() && "pred_iterator out of range!");
return cast<Instruction>(*It)->getParent();
}
inline pointer *operator->() const { return &operator*(); }
inline Self& operator++() { // Preincrement
assert(!It.atEnd() && "pred_iterator out of range!");
++It; advancePastNonTerminators();
return *this;
}
inline Self operator++(int) { // Postincrement
Self tmp = *this; ++*this; return tmp;
}
/// getOperandNo - Return the operand number in the predecessor's
/// terminator of the successor.
unsigned getOperandNo() const {
return It.getOperandNo();
}
/// getUse - Return the operand Use in the predecessor's terminator
/// of the successor.
Use &getUse() const {
return It.getUse();
}
};
using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>;
using const_pred_iterator =
PredIterator<const BasicBlock, Value::const_user_iterator>;
using pred_range = iterator_range<pred_iterator>;
using const_pred_range = iterator_range<const_pred_iterator>;
inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); }
inline const_pred_iterator pred_begin(const BasicBlock *BB) {
return const_pred_iterator(BB);
}
inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);}
inline const_pred_iterator pred_end(const BasicBlock *BB) {
return const_pred_iterator(BB, true);
}
inline bool pred_empty(const BasicBlock *BB) {
return pred_begin(BB) == pred_end(BB);
}
/// Get the number of predecessors of \p BB. This is a linear time operation.
/// Use \ref BasicBlock::hasNPredecessors() or hasNPredecessorsOrMore if able.
inline unsigned pred_size(const BasicBlock *BB) {
return std::distance(pred_begin(BB), pred_end(BB));
}
inline pred_range predecessors(BasicBlock *BB) {
return pred_range(pred_begin(BB), pred_end(BB));
}
inline const_pred_range predecessors(const BasicBlock *BB) {
return const_pred_range(pred_begin(BB), pred_end(BB));
}
//===----------------------------------------------------------------------===//
// Instruction and BasicBlock succ_iterator helpers
//===----------------------------------------------------------------------===//
template <class InstructionT, class BlockT>
class SuccIterator
: public iterator_facade_base<SuccIterator<InstructionT, BlockT>,
std::random_access_iterator_tag, BlockT, int,
BlockT *, BlockT *> {
public:
using difference_type = int;
using pointer = BlockT *;
using reference = BlockT *;
private:
InstructionT *Inst;
int Idx;
using Self = SuccIterator<InstructionT, BlockT>;
inline bool index_is_valid(int Idx) {
// Note that we specially support the index of zero being valid even in the
// face of a null instruction.
return Idx >= 0 && (Idx == 0 || Idx <= (int)Inst->getNumSuccessors());
}
/// Proxy object to allow write access in operator[]
class SuccessorProxy {
Self It;
public:
explicit SuccessorProxy(const Self &It) : It(It) {}
SuccessorProxy(const SuccessorProxy &) = default;
SuccessorProxy &operator=(SuccessorProxy RHS) {
*this = reference(RHS);
return *this;
}
SuccessorProxy &operator=(reference RHS) {
It.Inst->setSuccessor(It.Idx, RHS);
return *this;
}
operator reference() const { return *It; }
};
public:
// begin iterator
explicit inline SuccIterator(InstructionT *Inst) : Inst(Inst), Idx(0) {}
// end iterator
inline SuccIterator(InstructionT *Inst, bool) : Inst(Inst) {
if (Inst)
Idx = Inst->getNumSuccessors();
else
// Inst == NULL happens, if a basic block is not fully constructed and
// consequently getTerminator() returns NULL. In this case we construct
// a SuccIterator which describes a basic block that has zero
// successors.
// Defining SuccIterator for incomplete and malformed CFGs is especially
// useful for debugging.
Idx = 0;
}
/// This is used to interface between code that wants to
/// operate on terminator instructions directly.
int getSuccessorIndex() const { return Idx; }
inline bool operator==(const Self &x) const { return Idx == x.Idx; }
inline BlockT *operator*() const { return Inst->getSuccessor(Idx); }
// We use the basic block pointer directly for operator->.
inline BlockT *operator->() const { return operator*(); }
inline bool operator<(const Self &RHS) const {
assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
return Idx < RHS.Idx;
}
int operator-(const Self &RHS) const {
assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
return Idx - RHS.Idx;
}
inline Self &operator+=(int RHS) {
int NewIdx = Idx + RHS;
assert(index_is_valid(NewIdx) && "Iterator index out of bound");
Idx = NewIdx;
return *this;
}
inline Self &operator-=(int RHS) { return operator+=(-RHS); }
// Specially implement the [] operation using a proxy object to support
// assignment.
inline SuccessorProxy operator[](int Offset) {
Self TmpIt = *this;
TmpIt += Offset;
return SuccessorProxy(TmpIt);
}
/// Get the source BlockT of this iterator.
inline BlockT *getSource() {
assert(Inst && "Source not available, if basic block was malformed");
return Inst->getParent();
}
};
using succ_iterator = SuccIterator<Instruction, BasicBlock>;
using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>;
using succ_range = iterator_range<succ_iterator>;
using const_succ_range = iterator_range<const_succ_iterator>;
inline succ_iterator succ_begin(Instruction *I) { return succ_iterator(I); }
inline const_succ_iterator succ_begin(const Instruction *I) {
return const_succ_iterator(I);
}
inline succ_iterator succ_end(Instruction *I) { return succ_iterator(I, true); }
inline const_succ_iterator succ_end(const Instruction *I) {
return const_succ_iterator(I, true);
}
inline bool succ_empty(const Instruction *I) {
return succ_begin(I) == succ_end(I);
}
inline unsigned succ_size(const Instruction *I) {
return std::distance(succ_begin(I), succ_end(I));
}
inline succ_range successors(Instruction *I) {
return succ_range(succ_begin(I), succ_end(I));
}
inline const_succ_range successors(const Instruction *I) {
return const_succ_range(succ_begin(I), succ_end(I));
}
inline succ_iterator succ_begin(BasicBlock *BB) {
return succ_iterator(BB->getTerminator());
}
inline const_succ_iterator succ_begin(const BasicBlock *BB) {
return const_succ_iterator(BB->getTerminator());
}
inline succ_iterator succ_end(BasicBlock *BB) {
return succ_iterator(BB->getTerminator(), true);
}
inline const_succ_iterator succ_end(const BasicBlock *BB) {
return const_succ_iterator(BB->getTerminator(), true);
}
inline bool succ_empty(const BasicBlock *BB) {
return succ_begin(BB) == succ_end(BB);
}
inline unsigned succ_size(const BasicBlock *BB) {
return std::distance(succ_begin(BB), succ_end(BB));
}
inline succ_range successors(BasicBlock *BB) {
return succ_range(succ_begin(BB), succ_end(BB));
}
inline const_succ_range successors(const BasicBlock *BB) {
return const_succ_range(succ_begin(BB), succ_end(BB));
}
//===--------------------------------------------------------------------===//
// GraphTraits specializations for basic block graphs (CFGs)
//===--------------------------------------------------------------------===//
// Provide specializations of GraphTraits to be able to treat a function as a
// graph of basic blocks...
template <> struct GraphTraits<BasicBlock*> {
using NodeRef = BasicBlock *;
using ChildIteratorType = succ_iterator;
static NodeRef getEntryNode(BasicBlock *BB) { return BB; }
static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
};
template <> struct GraphTraits<const BasicBlock*> {
using NodeRef = const BasicBlock *;
using ChildIteratorType = const_succ_iterator;
static NodeRef getEntryNode(const BasicBlock *BB) { return BB; }
static ChildIteratorType child_begin(NodeRef N) { return succ_begin(N); }
static ChildIteratorType child_end(NodeRef N) { return succ_end(N); }
};
// Provide specializations of GraphTraits to be able to treat a function as a
// graph of basic blocks... and to walk it in inverse order. Inverse order for
// a function is considered to be when traversing the predecessor edges of a BB
// instead of the successor edges.
//
template <> struct GraphTraits<Inverse<BasicBlock*>> {
using NodeRef = BasicBlock *;
using ChildIteratorType = pred_iterator;
static NodeRef getEntryNode(Inverse<BasicBlock *> G) { return G.Graph; }
static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
};
template <> struct GraphTraits<Inverse<const BasicBlock*>> {
using NodeRef = const BasicBlock *;
using ChildIteratorType = const_pred_iterator;
static NodeRef getEntryNode(Inverse<const BasicBlock *> G) { return G.Graph; }
static ChildIteratorType child_begin(NodeRef N) { return pred_begin(N); }
static ChildIteratorType child_end(NodeRef N) { return pred_end(N); }
};
//===--------------------------------------------------------------------===//
// GraphTraits specializations for function basic block graphs (CFGs)
//===--------------------------------------------------------------------===//
// Provide specializations of GraphTraits to be able to treat a function as a
// graph of basic blocks... these are the same as the basic block iterators,
// except that the root node is implicitly the first node of the function.
//
template <> struct GraphTraits<Function*> : public GraphTraits<BasicBlock*> {
static NodeRef getEntryNode(Function *F) { return &F->getEntryBlock(); }
// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
using nodes_iterator = pointer_iterator<Function::iterator>;
static nodes_iterator nodes_begin(Function *F) {
return nodes_iterator(F->begin());
}
static nodes_iterator nodes_end(Function *F) {
return nodes_iterator(F->end());
}
static size_t size(Function *F) { return F->size(); }
};
template <> struct GraphTraits<const Function*> :
public GraphTraits<const BasicBlock*> {
static NodeRef getEntryNode(const Function *F) { return &F->getEntryBlock(); }
// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
using nodes_iterator = pointer_iterator<Function::const_iterator>;
static nodes_iterator nodes_begin(const Function *F) {
return nodes_iterator(F->begin());
}
static nodes_iterator nodes_end(const Function *F) {
return nodes_iterator(F->end());
}
static size_t size(const Function *F) { return F->size(); }
};
// Provide specializations of GraphTraits to be able to treat a function as a
// graph of basic blocks... and to walk it in inverse order. Inverse order for
// a function is considered to be when traversing the predecessor edges of a BB
// instead of the successor edges.
//
template <> struct GraphTraits<Inverse<Function*>> :
public GraphTraits<Inverse<BasicBlock*>> {
static NodeRef getEntryNode(Inverse<Function *> G) {
return &G.Graph->getEntryBlock();
}
};
template <> struct GraphTraits<Inverse<const Function*>> :
public GraphTraits<Inverse<const BasicBlock*>> {
static NodeRef getEntryNode(Inverse<const Function *> G) {
return &G.Graph->getEntryBlock();
}
};
} // end namespace llvm
#endif // LLVM_IR_CFG_H