1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 * vim: set ts=8 sts=2 et sw=2 tw=80:
3 * This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6
7 #include "frontend/OptionalEmitter.h"
8
9 #include "frontend/BytecodeEmitter.h"
10 #include "frontend/IfEmitter.h" // IfEmitter, InternalIfEmitter, CondEmitter
11 #include "frontend/SharedContext.h"
12 #include "vm/Opcodes.h"
13 #include "vm/StringType.h"
14
15 using namespace js;
16 using namespace js::frontend;
17
OptionalEmitter(BytecodeEmitter * bce,int32_t initialDepth)18 OptionalEmitter::OptionalEmitter(BytecodeEmitter* bce, int32_t initialDepth)
19 : bce_(bce), tdzCache_(bce), initialDepth_(initialDepth) {}
20
emitJumpShortCircuit()21 bool OptionalEmitter::emitJumpShortCircuit() {
22 MOZ_ASSERT(state_ == State::Start || state_ == State::ShortCircuit ||
23 state_ == State::ShortCircuitForCall);
24 MOZ_ASSERT(initialDepth_ + 1 == bce_->bytecodeSection().stackDepth());
25 InternalIfEmitter ifEmitter(bce_);
26 if (!bce_->emitPushNotUndefinedOrNull()) {
27 // [stack] OBJ NOT-UNDEFINED-OR-NULL
28 return false;
29 }
30
31 if (!bce_->emit1(JSOp::Not)) {
32 // [stack] OBJ UNDEFINED-OR-NULL
33 return false;
34 }
35
36 if (!ifEmitter.emitThen()) {
37 return false;
38 }
39
40 if (!bce_->emitJump(JSOp::Goto, &jumpShortCircuit_)) {
41 // [stack] UNDEFINED-OR-NULL
42 return false;
43 }
44
45 if (!ifEmitter.emitEnd()) {
46 return false;
47 }
48 #ifdef DEBUG
49 state_ = State::ShortCircuit;
50 #endif
51 return true;
52 }
53
emitJumpShortCircuitForCall()54 bool OptionalEmitter::emitJumpShortCircuitForCall() {
55 MOZ_ASSERT(state_ == State::Start || state_ == State::ShortCircuit ||
56 state_ == State::ShortCircuitForCall);
57 int32_t depth = bce_->bytecodeSection().stackDepth();
58 MOZ_ASSERT(initialDepth_ + 2 == depth);
59 if (!bce_->emit1(JSOp::Swap)) {
60 // [stack] THIS CALLEE
61 return false;
62 }
63
64 InternalIfEmitter ifEmitter(bce_);
65 if (!bce_->emitPushNotUndefinedOrNull()) {
66 // [stack] THIS CALLEE NOT-UNDEFINED-OR-NULL
67 return false;
68 }
69
70 if (!bce_->emit1(JSOp::Not)) {
71 // [stack] THIS CALLEE UNDEFINED-OR-NULL
72 return false;
73 }
74
75 if (!ifEmitter.emitThen()) {
76 return false;
77 }
78
79 if (!bce_->emit1(JSOp::Pop)) {
80 // [stack] THIS
81 return false;
82 }
83
84 if (!bce_->emitJump(JSOp::Goto, &jumpShortCircuit_)) {
85 // [stack] UNDEFINED-OR-NULL
86 return false;
87 }
88
89 if (!ifEmitter.emitEnd()) {
90 return false;
91 }
92
93 bce_->bytecodeSection().setStackDepth(depth);
94
95 if (!bce_->emit1(JSOp::Swap)) {
96 // [stack] THIS CALLEE
97 return false;
98 }
99 #ifdef DEBUG
100 state_ = State::ShortCircuitForCall;
101 #endif
102 return true;
103 }
104
emitOptionalJumpTarget(JSOp op,Kind kind)105 bool OptionalEmitter::emitOptionalJumpTarget(JSOp op,
106 Kind kind /* = Kind::Other */) {
107 #ifdef DEBUG
108 int32_t depth = bce_->bytecodeSection().stackDepth();
109 #endif
110 MOZ_ASSERT(state_ == State::ShortCircuit ||
111 state_ == State::ShortCircuitForCall);
112
113 // if we get to this point, it means that the optional chain did not short
114 // circuit, so we should skip the short circuiting bytecode.
115 if (!bce_->emitJump(JSOp::Goto, &jumpFinish_)) {
116 // [stack] # if call
117 // [stack] CALLEE THIS
118 // [stack] # otherwise, if defined
119 // [stack] VAL
120 // [stack] # otherwise
121 // [stack] UNDEFINED-OR-NULL
122 return false;
123 }
124
125 if (!bce_->emitJumpTargetAndPatch(jumpShortCircuit_)) {
126 // [stack] UNDEFINED-OR-NULL
127 return false;
128 }
129
130 // reset stack depth to the depth when we jumped
131 bce_->bytecodeSection().setStackDepth(initialDepth_ + 1);
132
133 if (!bce_->emit1(JSOp::Pop)) {
134 // [stack]
135 return false;
136 }
137
138 if (!bce_->emit1(op)) {
139 // [stack] JSOP
140 return false;
141 }
142
143 if (kind == Kind::Reference) {
144 if (!bce_->emit1(op)) {
145 // [stack] JSOP JSOP
146 return false;
147 }
148 }
149
150 MOZ_ASSERT(depth == bce_->bytecodeSection().stackDepth());
151
152 if (!bce_->emitJumpTargetAndPatch(jumpFinish_)) {
153 // [stack] # if call
154 // [stack] CALLEE THIS
155 // [stack] # otherwise
156 // [stack] VAL
157 return false;
158 }
159 #ifdef DEBUG
160 state_ = State::JumpEnd;
161 #endif
162 return true;
163 }
164