summaryrefslogtreecommitdiffstats
path: root/js/src/frontend/OptionalEmitter.cpp
blob: 6fe5924099b73cbbe41cafe06ba90df56d547b76 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "frontend/OptionalEmitter.h"

#include "frontend/BytecodeEmitter.h"
#include "frontend/IfEmitter.h"  // IfEmitter, InternalIfEmitter, CondEmitter
#include "vm/Opcodes.h"

using namespace js;
using namespace js::frontend;

OptionalEmitter::OptionalEmitter(BytecodeEmitter* bce, int32_t initialDepth)
    : bce_(bce), tdzCache_(bce), initialDepth_(initialDepth) {}

bool OptionalEmitter::emitJumpShortCircuit() {
  MOZ_ASSERT(state_ == State::Start || state_ == State::ShortCircuit ||
             state_ == State::ShortCircuitForCall);
  MOZ_ASSERT(initialDepth_ + 1 == bce_->bytecodeSection().stackDepth());

  if (!bce_->emit1(JSOp::IsNullOrUndefined)) {
    //              [stack] OBJ NULL-OR-UNDEF
    return false;
  }
  if (!bce_->emitJump(JSOp::JumpIfTrue, &jumpShortCircuit_)) {
    //              [stack] OBJ
    return false;
  }

#ifdef DEBUG
  state_ = State::ShortCircuit;
#endif
  return true;
}

bool OptionalEmitter::emitJumpShortCircuitForCall() {
  MOZ_ASSERT(state_ == State::Start || state_ == State::ShortCircuit ||
             state_ == State::ShortCircuitForCall);
  int32_t depth = bce_->bytecodeSection().stackDepth();
  MOZ_ASSERT(initialDepth_ + 2 == depth);
  if (!bce_->emit1(JSOp::Swap)) {
    //              [stack] THIS CALLEE
    return false;
  }

  InternalIfEmitter ifEmitter(bce_);
  if (!bce_->emit1(JSOp::IsNullOrUndefined)) {
    //              [stack] THIS CALLEE NULL-OR-UNDEF
    return false;
  }

  if (!ifEmitter.emitThen()) {
    //              [stack] THIS CALLEE
    return false;
  }

  if (!bce_->emit1(JSOp::Pop)) {
    //              [stack] THIS
    return false;
  }

  if (!bce_->emitJump(JSOp::Goto, &jumpShortCircuit_)) {
    //              [stack] THIS
    return false;
  }

  if (!ifEmitter.emitEnd()) {
    return false;
  }

  bce_->bytecodeSection().setStackDepth(depth);

  if (!bce_->emit1(JSOp::Swap)) {
    //              [stack] THIS CALLEE
    return false;
  }
#ifdef DEBUG
  state_ = State::ShortCircuitForCall;
#endif
  return true;
}

bool OptionalEmitter::emitOptionalJumpTarget(JSOp op,
                                             Kind kind /* = Kind::Other */) {
#ifdef DEBUG
  int32_t depth = bce_->bytecodeSection().stackDepth();
#endif
  MOZ_ASSERT(state_ == State::ShortCircuit ||
             state_ == State::ShortCircuitForCall);

  // if we get to this point, it means that the optional chain did not short
  // circuit, so we should skip the short circuiting bytecode.
  if (!bce_->emitJump(JSOp::Goto, &jumpFinish_)) {
    //              [stack] RESULT
    return false;
  }

  if (!bce_->emitJumpTargetAndPatch(jumpShortCircuit_)) {
    //              [stack] # if call
    //              [stack] THIS
    //              [stack] # otherwise
    //              [stack] OBJ
    return false;
  }

  // reset stack depth to the depth when we jumped
  bce_->bytecodeSection().setStackDepth(initialDepth_ + 1);

  if (!bce_->emit1(JSOp::Pop)) {
    //              [stack]
    return false;
  }

  if (!bce_->emit1(op)) {
    //              [stack] JSOP
    return false;
  }

  if (kind == Kind::Reference) {
    if (!bce_->emit1(op)) {
      //            [stack] JSOP JSOP
      return false;
    }
  }

  MOZ_ASSERT(depth == bce_->bytecodeSection().stackDepth());

  if (!bce_->emitJumpTargetAndPatch(jumpFinish_)) {
    //              [stack] # if call
    //              [stack] CALLEE THIS
    //              [stack] # otherwise
    //              [stack] VAL
    return false;
  }
#ifdef DEBUG
  state_ = State::JumpEnd;
#endif
  return true;
}