1//=== InstructionWorklist.h - Worklist for InstCombine & others -*- 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_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H
10#define LLVM_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H
11
12#include "llvm/ADT/DenseMap.h"
13#include "llvm/ADT/STLExtras.h"
14#include "llvm/ADT/SetVector.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/IR/Instruction.h"
17#include "llvm/Support/Compiler.h"
18#include "llvm/Support/Debug.h"
19#include "llvm/Support/raw_ostream.h"
20
21namespace llvm {
22
23/// InstructionWorklist - This is the worklist management logic for
24/// InstCombine and other simplification passes.
25class InstructionWorklist {
26 SmallVector<Instruction *, 256> Worklist;
27 DenseMap<Instruction *, unsigned> WorklistMap;
28 /// These instructions will be added in reverse order after the current
29 /// combine has finished. This means that these instructions will be visited
30 /// in the order they have been added.
31 SmallSetVector<Instruction *, 16> Deferred;
32
33public:
34 InstructionWorklist() = default;
35
36 InstructionWorklist(InstructionWorklist &&) = default;
37 InstructionWorklist &operator=(InstructionWorklist &&) = default;
38
39 bool isEmpty() const { return Worklist.empty() && Deferred.empty(); }
40
41 /// Add instruction to the worklist.
42 /// Instructions will be visited in the order they are added.
43 /// You likely want to use this method.
44 void add(Instruction *I) {
45 if (Deferred.insert(X: I))
46 LLVM_DEBUG(dbgs() << "ADD DEFERRED: " << *I << '\n');
47 }
48
49 /// Add value to the worklist if it is an instruction.
50 /// Instructions will be visited in the order they are added.
51 void addValue(Value *V) {
52 if (Instruction *I = dyn_cast<Instruction>(Val: V))
53 add(I);
54 }
55
56 /// Push the instruction onto the worklist stack.
57 /// Instructions that have been added first will be visited last.
58 void push(Instruction *I) {
59 assert(I);
60 assert(I->getParent() && "Instruction not inserted yet?");
61
62 if (WorklistMap.insert(KV: std::make_pair(x&: I, y: Worklist.size())).second) {
63 LLVM_DEBUG(dbgs() << "ADD: " << *I << '\n');
64 Worklist.push_back(Elt: I);
65 }
66 }
67
68 void pushValue(Value *V) {
69 if (Instruction *I = dyn_cast<Instruction>(Val: V))
70 push(I);
71 }
72
73 Instruction *popDeferred() {
74 if (Deferred.empty())
75 return nullptr;
76 return Deferred.pop_back_val();
77 }
78
79 void reserve(size_t Size) {
80 Worklist.reserve(N: Size + 16);
81 WorklistMap.reserve(NumEntries: Size);
82 }
83
84 /// Remove I from the worklist if it exists.
85 void remove(Instruction *I) {
86 DenseMap<Instruction *, unsigned>::iterator It = WorklistMap.find(Val: I);
87 if (It != WorklistMap.end()) {
88 // Don't bother moving everything down, just null out the slot.
89 Worklist[It->second] = nullptr;
90 WorklistMap.erase(I: It);
91 }
92
93 Deferred.remove(X: I);
94 }
95
96 Instruction *removeOne() {
97 if (Worklist.empty())
98 return nullptr;
99 Instruction *I = Worklist.pop_back_val();
100 WorklistMap.erase(Val: I);
101 return I;
102 }
103
104 /// When an instruction is simplified, add all users of the instruction
105 /// to the work lists because they might get more simplified now.
106 void pushUsersToWorkList(Instruction &I) {
107 for (User *U : I.users())
108 push(I: cast<Instruction>(Val: U));
109 }
110
111 /// Should be called *after* decrementing the use-count on V.
112 void handleUseCountDecrement(Value *V) {
113 if (auto *I = dyn_cast<Instruction>(Val: V)) {
114 add(I);
115 // Many folds have one-use limitations. If there's only one use left,
116 // revisit that use.
117 if (I->hasOneUse())
118 add(I: cast<Instruction>(Val: *I->user_begin()));
119 }
120 }
121
122 /// Check that the worklist is empty and nuke the backing store for the map.
123 void zap() {
124 assert(WorklistMap.empty() && "Worklist empty, but map not?");
125 assert(Deferred.empty() && "Deferred instructions left over");
126
127 // Do an explicit clear, this shrinks the map if needed.
128 WorklistMap.clear();
129 }
130};
131
132} // end namespace llvm.
133
134#endif
135