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//===- IntervalPartition.h - Interval partition Calculation -----*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file contains the declaration of the IntervalPartition class, which
// calculates and represents the interval partition of a function, or a
// preexisting interval partition.
// In this way, the interval partition may be used to reduce a flow graph down
// to its degenerate single node interval partition (unless it is irreducible).
// TODO: The IntervalPartition class should take a bool parameter that tells
// whether it should add the "tails" of an interval to an interval itself or if
// they should be represented as distinct intervals.
#include "llvm/Pass.h"
#include <map>
#include <vector>
namespace llvm {
class BasicBlock;
class Interval;
// IntervalPartition - This class builds and holds an "interval partition" for
// a function. This partition divides the control flow graph into a set of
// maximal intervals, as defined with the properties above. Intuitively, an
// interval is a (possibly nonexistent) loop with a "tail" of non-looping
// nodes following it.
class IntervalPartition : public FunctionPass {
using IntervalMapTy = std::map<BasicBlock *, Interval *>;
IntervalMapTy IntervalMap;
using IntervalListTy = std::vector<Interval *>;
Interval *RootInterval = nullptr;
std::vector<Interval *> Intervals;
static char ID; // Pass identification, replacement for typeid
IntervalPartition() : FunctionPass(ID) {
// run - Calculate the interval partition for this function
bool runOnFunction(Function &F) override;
// IntervalPartition ctor - Build a reduced interval partition from an
// existing interval graph. This takes an additional boolean parameter to
// distinguish it from a copy constructor. Always pass in false for now.
IntervalPartition(IntervalPartition &I, bool);
// print - Show contents in human readable format...
void print(raw_ostream &O, const Module* = nullptr) const override;
// getRootInterval() - Return the root interval that contains the starting
// block of the function.
inline Interval *getRootInterval() { return RootInterval; }
// isDegeneratePartition() - Returns true if the interval partition contains
// a single interval, and thus cannot be simplified anymore.
bool isDegeneratePartition() { return Intervals.size() == 1; }
// TODO: isIrreducible - look for triangle graph.
// getBlockInterval - Return the interval that a basic block exists in.
inline Interval *getBlockInterval(BasicBlock *BB) {
IntervalMapTy::iterator I = IntervalMap.find(BB);
return I != IntervalMap.end() ? I->second : nullptr;
// getAnalysisUsage - Implement the Pass API
void getAnalysisUsage(AnalysisUsage &AU) const override {
// Interface to Intervals vector...
const std::vector<Interval*> &getIntervals() const { return Intervals; }
// releaseMemory - Reset state back to before function was analyzed
void releaseMemory() override;
// addIntervalToPartition - Add an interval to the internal list of intervals,
// and then add mappings from all of the basic blocks in the interval to the
// interval itself (in the IntervalMap).
void addIntervalToPartition(Interval *I);
// updatePredecessors - Interval generation only sets the successor fields of
// the interval data structures. After interval generation is complete,
// run through all of the intervals and propagate successor info as
// predecessor info.
void updatePredecessors(Interval *Int);
} // end namespace llvm