include/llvm/Analysis/IntervalPartition.h

   1 //===- IntervalPartition.h - Interval partition Calculation -----*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains the declaration of the IntervalPartition class, which
  10 // calculates and represents the interval partition of a function, or a
  11 // preexisting interval partition.
  12 //
  13 // In this way, the interval partition may be used to reduce a flow graph down
  14 // to its degenerate single node interval partition (unless it is irreducible).
  15 //
  16 // TODO: The IntervalPartition class should take a bool parameter that tells
  17 // whether it should add the "tails" of an interval to an interval itself or if
  18 // they should be represented as distinct intervals.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #ifndef LLVM_ANALYSIS_INTERVALPARTITION_H
  23 #define LLVM_ANALYSIS_INTERVALPARTITION_H
  24
  25 #include "llvm/Pass.h"
  26 #include <map>
  27 #include <vector>
  28
  29 namespace llvm {
  30
  31 class BasicBlock;
  32 class Interval;
  33
  34 //===----------------------------------------------------------------------===//
  35 //
  36 // IntervalPartition - This class builds and holds an "interval partition" for
  37 // a function.  This partition divides the control flow graph into a set of
  38 // maximal intervals, as defined with the properties above.  Intuitively, an
  39 // interval is a (possibly nonexistent) loop with a "tail" of non-looping
  40 // nodes following it.
  41 //
  42 class IntervalPartition : public FunctionPass {
  43   using IntervalMapTy = std::map<BasicBlock *, Interval *>;
  44   IntervalMapTy IntervalMap;
  45
  46   using IntervalListTy = std::vector<Interval *>;
  47   Interval *RootInterval = nullptr;
  48   std::vector<Interval *> Intervals;
  49
  50 public:
  51   static char ID; // Pass identification, replacement for typeid
  52
  53   IntervalPartition() : FunctionPass(ID) {
  54     initializeIntervalPartitionPass(*PassRegistry::getPassRegistry());
  55   }
  56
  57   // run - Calculate the interval partition for this function
  58   bool runOnFunction(Function &F) override;
  59
  60   // IntervalPartition ctor - Build a reduced interval partition from an
  61   // existing interval graph.  This takes an additional boolean parameter to
  62   // distinguish it from a copy constructor.  Always pass in false for now.
  63   IntervalPartition(IntervalPartition &I, bool);
  64
  65   // print - Show contents in human readable format...
  66   void print(raw_ostream &O, const Module* = nullptr) const override;
  67
  68   // getRootInterval() - Return the root interval that contains the starting
  69   // block of the function.
  70   inline Interval *getRootInterval() { return RootInterval; }
  71
  72   // isDegeneratePartition() - Returns true if the interval partition contains
  73   // a single interval, and thus cannot be simplified anymore.
  74   bool isDegeneratePartition() { return Intervals.size() == 1; }
  75
  76   // TODO: isIrreducible - look for triangle graph.
  77
  78   // getBlockInterval - Return the interval that a basic block exists in.
  79   inline Interval *getBlockInterval(BasicBlock *BB) {
  80     IntervalMapTy::iterator I = IntervalMap.find(BB);
  81     return I != IntervalMap.end() ? I->second : nullptr;
  82   }
  83
  84   // getAnalysisUsage - Implement the Pass API
  85   void getAnalysisUsage(AnalysisUsage &AU) const override {
  86     AU.setPreservesAll();
  87   }
  88
  89   // Interface to Intervals vector...
  90   const std::vector<Interval*> &getIntervals() const { return Intervals; }
  91
  92   // releaseMemory - Reset state back to before function was analyzed
  93   void releaseMemory() override;
  94
  95 private:
  96   // addIntervalToPartition - Add an interval to the internal list of intervals,
  97   // and then add mappings from all of the basic blocks in the interval to the
  98   // interval itself (in the IntervalMap).
  99   void addIntervalToPartition(Interval *I);
 100
 101   // updatePredecessors - Interval generation only sets the successor fields of
 102   // the interval data structures.  After interval generation is complete,
 103   // run through all of the intervals and propagate successor info as
 104   // predecessor info.
 105   void updatePredecessors(Interval *Int);
 106 };
 107
 108 } // end namespace llvm
 109
 110 #endif // LLVM_ANALYSIS_INTERVALPARTITION_H