//===- IntervalIterator.h - Interval Iterator Declaration -------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines an iterator that enumerates the intervals in a control flow
// graph of some sort. This iterator is parametric, allowing iterator over the
// following types of graphs:
//
// 1. A Function* object, composed of BasicBlock nodes.
// 2. An IntervalPartition& object, composed of Interval nodes.
//
// This iterator is defined to walk the control flow graph, returning intervals
// in depth first order. These intervals are completely filled in except for
// the predecessor fields (the successor information is filled in however).
//
// By default, the intervals created by this iterator are deleted after they
// are no longer any use to the iterator. This behavior can be changed by
// passing a false value into the intervals_begin() function. This causes the
// IOwnMem member to be set, and the intervals to not be deleted.
//
// It is only safe to use this if all of the intervals are deleted by the caller
// and all of the intervals are processed. However, the user of the iterator is
// not allowed to modify or delete the intervals until after the iterator has
// been used completely. The IntervalPartition class uses this functionality.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_INTERVALITERATOR_H
#define LLVM_ANALYSIS_INTERVALITERATOR_H
#include "llvm/ADT/GraphTraits.h"
#include "llvm/Analysis/Interval.h"
#include "llvm/Analysis/IntervalPartition.h"
#include "llvm/IR/CFG.h"
#include <algorithm>
#include <cassert>
#include <iterator>
#include <set>
#include <utility>
#include <vector>
namespace llvm {
class BasicBlock;
class Function;
// getNodeHeader - Given a source graph node and the source graph, return the
// BasicBlock that is the header node. This is the opposite of
// getSourceGraphNode.
inline BasicBlock *getNodeHeader(BasicBlock *BB) { return BB; }
inline BasicBlock *getNodeHeader(Interval *I) { return I->getHeaderNode(); }
// getSourceGraphNode - Given a BasicBlock and the source graph, return the
// source graph node that corresponds to the BasicBlock. This is the opposite
// of getNodeHeader.
inline BasicBlock *getSourceGraphNode(Function *, BasicBlock *BB) {
return BB;
}
inline Interval *getSourceGraphNode(IntervalPartition *IP, BasicBlock *BB) {
return IP->getBlockInterval(BB);
}
// addNodeToInterval - This method exists to assist the generic ProcessNode
// with the task of adding a node to the new interval, depending on the
// type of the source node. In the case of a CFG source graph (BasicBlock
// case), the BasicBlock itself is added to the interval.
inline void addNodeToInterval(Interval *Int, BasicBlock *BB) {
Int->Nodes.push_back(BB);
}
// addNodeToInterval - This method exists to assist the generic ProcessNode
// with the task of adding a node to the new interval, depending on the
// type of the source node. In the case of a CFG source graph (BasicBlock
// case), the BasicBlock itself is added to the interval. In the case of
// an IntervalPartition source graph (Interval case), all of the member
// BasicBlocks are added to the interval.
inline void addNodeToInterval(Interval *Int, Interval *I) {
// Add all of the nodes in I as new nodes in Int.
llvm::append_range(Int->Nodes, I->Nodes);
}
template<class NodeTy, class OrigContainer_t, class GT = GraphTraits<NodeTy *>,
class IGT = GraphTraits<Inverse<NodeTy *>>>
class IntervalIterator {
std::vector<std::pair<Interval *, typename Interval::succ_iterator>> IntStack;
std::set<BasicBlock *> Visited;
OrigContainer_t *OrigContainer;
bool IOwnMem; // If True, delete intervals when done with them
// See file header for conditions of use
public:
using iterator_category = std::forward_iterator_tag;
IntervalIterator() = default; // End iterator, empty stack
IntervalIterator(Function *M, bool OwnMemory) : IOwnMem(OwnMemory) {
OrigContainer = M;
if (!ProcessInterval(&M->front())) {
llvm_unreachable("ProcessInterval should never fail for first interval!");
}
}
IntervalIterator(IntervalIterator &&x)
: IntStack(std::move(x.IntStack)), Visited(std::move(x.Visited)),
OrigContainer(x.OrigContainer), IOwnMem(x.IOwnMem) {
x.IOwnMem = false;
}
IntervalIterator(IntervalPartition &IP, bool OwnMemory) : IOwnMem(OwnMemory) {
OrigContainer = &IP;
if (!ProcessInterval(IP.getRootInterval())) {
llvm_unreachable("ProcessInterval should never fail for first interval!");
}
}
~IntervalIterator() {
if (IOwnMem)
while (!IntStack.empty()) {
delete operator*();
IntStack.pop_back();
}
}
bool operator==(const IntervalIterator &x) const {
return IntStack == x.IntStack;
}
bool operator!=(const IntervalIterator &x) const { return !(*this == x); }
const Interval *operator*() const { return IntStack.back().first; }
Interval *operator*() { return IntStack.back().first; }
const Interval *operator->() const { return operator*(); }
Interval *operator->() { return operator*(); }
IntervalIterator &operator++() { // Preincrement
assert(!IntStack.empty() && "Attempting to use interval iterator at end!");
do {
// All of the intervals on the stack have been visited. Try visiting
// their successors now.
Interval::succ_iterator &SuccIt = IntStack.back().second,
EndIt = succ_end(IntStack.back().first);
while (SuccIt != EndIt) { // Loop over all interval succs
bool Done = ProcessInterval(getSourceGraphNode(OrigContainer, *SuccIt));
++SuccIt; // Increment iterator
if (Done) return *this; // Found a new interval! Use it!
}
// Free interval memory... if necessary
if (IOwnMem) delete IntStack.back().first;
// We ran out of successors for this interval... pop off the stack
IntStack.pop_back();
} while (!IntStack.empty());
return *this;
}
IntervalIterator operator++(int) { // Postincrement
IntervalIterator tmp = *this;
++*this;
return tmp;
}
private:
// ProcessInterval - This method is used during the construction of the
// interval graph. It walks through the source graph, recursively creating
// an interval per invocation until the entire graph is covered. This uses
// the ProcessNode method to add all of the nodes to the interval.
//
// This method is templated because it may operate on two different source
// graphs: a basic block graph, or a preexisting interval graph.
bool ProcessInterval(NodeTy *Node) {
BasicBlock *Header = getNodeHeader(Node);
if (!Visited.insert(Header).second)
return false;
Interval *Int = new Interval(Header);
// Check all of our successors to see if they are in the interval...
for (typename GT::ChildIteratorType I = GT::child_begin(Node),
E = GT::child_end(Node); I != E; ++I)
ProcessNode(Int, getSourceGraphNode(OrigContainer, *I));
IntStack.push_back(std::make_pair(Int, succ_begin(Int)));
return true;
}
// ProcessNode - This method is called by ProcessInterval to add nodes to the
// interval being constructed, and it is also called recursively as it walks
// the source graph. A node is added to the current interval only if all of
// its predecessors are already in the graph. This also takes care of keeping
// the successor set of an interval up to date.
//
// This method is templated because it may operate on two different source
// graphs: a basic block graph, or a preexisting interval graph.
void ProcessNode(Interval *Int, NodeTy *Node) {
assert(Int && "Null interval == bad!");
assert(Node && "Null Node == bad!");
BasicBlock *NodeHeader = getNodeHeader(Node);
if (Visited.count(NodeHeader)) { // Node already been visited?
if (Int->contains(NodeHeader)) { // Already in this interval...
return;
} else { // In other interval, add as successor
if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
Int->Successors.push_back(NodeHeader);
}
} else { // Otherwise, not in interval yet
for (typename IGT::ChildIteratorType I = IGT::child_begin(Node),
E = IGT::child_end(Node); I != E; ++I) {
if (!Int->contains(*I)) { // If pred not in interval, we can't be
if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
Int->Successors.push_back(NodeHeader);
return; // See you later
}
}
// If we get here, then all of the predecessors of BB are in the interval
// already. In this case, we must add BB to the interval!
addNodeToInterval(Int, Node);
Visited.insert(NodeHeader); // The node has now been visited!
if (Int->isSuccessor(NodeHeader)) {
// If we were in the successor list from before... remove from succ list
llvm::erase_value(Int->Successors, NodeHeader);
}
// Now that we have discovered that Node is in the interval, perhaps some
// of its successors are as well?
for (typename GT::ChildIteratorType It = GT::child_begin(Node),
End = GT::child_end(Node); It != End; ++It)
ProcessNode(Int, getSourceGraphNode(OrigContainer, *It));
}
}
};
using function_interval_iterator = IntervalIterator<BasicBlock, Function>;
using interval_part_interval_iterator =
IntervalIterator<Interval, IntervalPartition>;
inline function_interval_iterator intervals_begin(Function *F,
bool DeleteInts = true) {
return function_interval_iterator(F, DeleteInts);
}
inline function_interval_iterator intervals_end(Function *) {
return function_interval_iterator();
}
inline interval_part_interval_iterator
intervals_begin(IntervalPartition &IP, bool DeleteIntervals = true) {
return interval_part_interval_iterator(IP, DeleteIntervals);
}
inline interval_part_interval_iterator intervals_end(IntervalPartition &IP) {
return interval_part_interval_iterator();
}
} // end namespace llvm
#endif // LLVM_ANALYSIS_INTERVALITERATOR_H