1//===- GISelWorkList.h - Worklist for GISel passes ----*- 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#ifndef LLVM_GISEL_WORKLIST_H
10#define LLVM_GISEL_WORKLIST_H
11
12#include "llvm/ADT/DenseMap.h"
13#include "llvm/ADT/SmallVector.h"
14#include "llvm/CodeGen/MachineBasicBlock.h"
15#include "llvm/CodeGen/MachineInstr.h"
16#include "llvm/Support/Debug.h"
17
18namespace llvm {
19
20class MachineInstr;
21class MachineFunction;
22
23// Worklist which mostly works similar to InstCombineWorkList, but on
24// MachineInstrs. The main difference with something like a SetVector is that
25// erasing an element doesn't move all elements over one place - instead just
26// nulls out the element of the vector.
27//
28// FIXME: Does it make sense to factor out common code with the
29// instcombinerWorkList?
30template<unsigned N>
31class GISelWorkList {
32  SmallVector<MachineInstr *, N> Worklist;
33  DenseMap<MachineInstr *, unsigned> WorklistMap;
34
35#ifndef NDEBUG
36  bool Finalized = true;
37#endif
38
39public:
40  GISelWorkList() : WorklistMap(N) {}
41
42  bool empty() const { return WorklistMap.empty(); }
43
44  unsigned size() const { return WorklistMap.size(); }
45
46  // Since we don't know ahead of time how many instructions we're going to add
47  // to the worklist, and migrating densemap's elements is quite expensive
48  // everytime we resize, only insert to the smallvector (typically during the
49  // initial phase of populating lists). Before the worklist can be used,
50  // finalize should be called. Also assert with NDEBUG if list is ever used
51  // without finalizing. Note that unlike insert, we won't check for duplicates
52  // - so the ideal place to use this is during the initial prepopulating phase
53  // of most passes.
54  void deferred_insert(MachineInstr *I) {
55    Worklist.push_back(I);
56#ifndef NDEBUG
57    Finalized = false;
58#endif
59  }
60
61  // This should only be called when using deferred_insert.
62  // This asserts that the WorklistMap is empty, and then
63  // inserts all the elements in the Worklist into the map.
64  // It also asserts if there are any duplicate elements found.
65  void finalize() {
66    assert(WorklistMap.empty() && "Expecting empty worklistmap");
67    if (Worklist.size() > N)
68      WorklistMap.reserve(Worklist.size());
69    for (unsigned i = 0; i < Worklist.size(); ++i)
70      if (!WorklistMap.try_emplace(Worklist[i], i).second)
71        llvm_unreachable("Duplicate elements in the list");
72#ifndef NDEBUG
73    Finalized = true;
74#endif
75  }
76
77  /// Add the specified instruction to the worklist if it isn't already in it.
78  void insert(MachineInstr *I) {
79    assert(Finalized && "GISelWorkList used without finalizing");
80    if (WorklistMap.try_emplace(I, Worklist.size()).second)
81      Worklist.push_back(I);
82  }
83
84  /// Remove I from the worklist if it exists.
85  void remove(const MachineInstr *I) {
86    assert((Finalized || WorklistMap.empty()) && "Neither finalized nor empty");
87    auto It = WorklistMap.find(I);
88    if (It == WorklistMap.end())
89      return; // Not in worklist.
90
91    // Don't bother moving everything down, just null out the slot.
92    Worklist[It->second] = nullptr;
93
94    WorklistMap.erase(It);
95  }
96
97  void clear() {
98    Worklist.clear();
99    WorklistMap.clear();
100  }
101
102  MachineInstr *pop_back_val() {
103    assert(Finalized && "GISelWorkList used without finalizing");
104    MachineInstr *I;
105    do {
106      I = Worklist.pop_back_val();
107    } while(!I);
108    assert(I && "Pop back on empty worklist");
109    WorklistMap.erase(I);
110    return I;
111  }
112};
113
114} // end namespace llvm.
115
116#endif
117