js/src/frontend/WhileEmitter.cpp

   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/WhileEmitter.h"
   8
   9 #include "frontend/BytecodeEmitter.h"
  10 #include "vm/Opcodes.h"
  11 #include "vm/StencilEnums.h"  // TryNoteKind
  12
  13 using namespace js;
  14 using namespace js::frontend;
  15
  16 WhileEmitter::WhileEmitter(BytecodeEmitter* bce) : bce_(bce) {}
  17
  18 bool WhileEmitter::emitCond(uint32_t whilePos, uint32_t condPos,
  19                             uint32_t endPos) {
  20   MOZ_ASSERT(state_ == State::Start);
  21
  22   // If we have a single-line while, like "while (x) ;", we want to emit the
  23   // line note before the loop, so that the debugger sees a single entry point.
  24   // This way, if there is a breakpoint on the line, it will only fire once; and
  25   // "next"ing will skip the whole loop. However, for the multi-line case we
  26   // want to emit the line note for the JSOp::LoopHead, so that "cont" stops on
  27   // each iteration -- but without a stop before the first iteration.
  28   if (bce_->errorReporter().lineAt(whilePos) ==
  29       bce_->errorReporter().lineAt(endPos)) {
  30     if (!bce_->updateSourceCoordNotes(whilePos)) {
  31       return false;
  32     }
  33     // Emit a Nop to ensure the source position is not part of the loop.
  34     if (!bce_->emit1(JSOp::Nop)) {
  35       return false;
  36     }
  37   }
  38
  39   loopInfo_.emplace(bce_, StatementKind::WhileLoop);
  40
  41   if (!loopInfo_->emitLoopHead(bce_, mozilla::Some(condPos))) {
  42     return false;
  43   }
  44
  45 #ifdef DEBUG
  46   state_ = State::Cond;
  47 #endif
  48   return true;
  49 }
  50
  51 bool WhileEmitter::emitBody() {
  52   MOZ_ASSERT(state_ == State::Cond);
  53
  54   if (!bce_->emitJump(JSOp::JumpIfFalse, &loopInfo_->breaks)) {
  55     return false;
  56   }
  57
  58   tdzCacheForBody_.emplace(bce_);
  59
  60 #ifdef DEBUG
  61   state_ = State::Body;
  62 #endif
  63   return true;
  64 }
  65
  66 bool WhileEmitter::emitEnd() {
  67   MOZ_ASSERT(state_ == State::Body);
  68
  69   tdzCacheForBody_.reset();
  70
  71   if (!loopInfo_->emitContinueTarget(bce_)) {
  72     return false;
  73   }
  74
  75   if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::Loop)) {
  76     return false;
  77   }
  78
  79   loopInfo_.reset();
  80
  81 #ifdef DEBUG
  82   state_ = State::End;
  83 #endif
  84   return true;
  85 }
  86
  87 #ifdef ENABLE_DECORATORS
  88 bool InternalWhileEmitter::emitCond() {
  89   MOZ_ASSERT(state_ == State::Start);
  90
  91   loopInfo_.emplace(bce_, StatementKind::WhileLoop);
  92
  93   if (!loopInfo_->emitLoopHead(bce_, mozilla::Nothing())) {
  94     return false;
  95   }
  96
  97 #  ifdef DEBUG
  98   state_ = State::Cond;
  99 #  endif
 100   return true;
 101 }
 102 #endif