1 files changed, 85 insertions, 0 deletions
diff --git a/js/src/frontend/WhileEmitter.cpp b/js/src/frontend/WhileEmitter.cpp
new file mode 100644
index 0000000000..bc002b2ea6
--- /dev/null
+++ b/js/src/frontend/WhileEmitter.cpp
@@ -0,0 +1,85 @@
+/* -*- 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/WhileEmitter.h"
+
+#include "frontend/BytecodeEmitter.h"
+#include "vm/Opcodes.h"
+#include "vm/StencilEnums.h"  // TryNoteKind
+
+using namespace js;
+using namespace js::frontend;
+
+WhileEmitter::WhileEmitter(BytecodeEmitter* bce) : bce_(bce) {}
+
+bool WhileEmitter::emitCond(uint32_t whilePos, uint32_t condPos,
+                            uint32_t endPos) {
+  MOZ_ASSERT(state_ == State::Start);
+
+  // If we have a single-line while, like "while (x) ;", we want to emit the
+  // line note before the loop, so that the debugger sees a single entry point.
+  // This way, if there is a breakpoint on the line, it will only fire once; and
+  // "next"ing will skip the whole loop. However, for the multi-line case we
+  // want to emit the line note for the JSOp::LoopHead, so that "cont" stops on
+  // each iteration -- but without a stop before the first iteration.
+  if (bce_->errorReporter().lineAt(whilePos) ==
+      bce_->errorReporter().lineAt(endPos)) {
+    if (!bce_->updateSourceCoordNotes(whilePos)) {
+      return false;
+    }
+    // Emit a Nop to ensure the source position is not part of the loop.
+    if (!bce_->emit1(JSOp::Nop)) {
+      return false;
+    }
+  }
+
+  loopInfo_.emplace(bce_, StatementKind::WhileLoop);
+
+  if (!loopInfo_->emitLoopHead(bce_, mozilla::Some(condPos))) {
+    return false;
+  }
+
+#ifdef DEBUG
+  state_ = State::Cond;
+#endif
+  return true;
+}
+
+bool WhileEmitter::emitBody() {
+  MOZ_ASSERT(state_ == State::Cond);
+
+  if (!bce_->emitJump(JSOp::JumpIfFalse, &loopInfo_->breaks)) {
+    return false;
+  }
+
+  tdzCacheForBody_.emplace(bce_);
+
+#ifdef DEBUG
+  state_ = State::Body;
+#endif
+  return true;
+}
+
+bool WhileEmitter::emitEnd() {
+  MOZ_ASSERT(state_ == State::Body);
+
+  tdzCacheForBody_.reset();
+
+  if (!loopInfo_->emitContinueTarget(bce_)) {
+    return false;
+  }
+
+  if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::Loop)) {
+    return false;
+  }
+
+  loopInfo_.reset();
+
+#ifdef DEBUG
+  state_ = State::End;
+#endif
+  return true;
+}