1 files changed, 48 insertions, 0 deletions
diff --git a/js/src/frontend/JumpList.cpp b/js/src/frontend/JumpList.cpp
new file mode 100644
index 0000000000..a5cb4ef6ad
--- /dev/null
+++ b/js/src/frontend/JumpList.cpp
@@ -0,0 +1,48 @@
+/* -*- 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/JumpList.h"
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+
+#include <stddef.h>  // ptrdiff_t
+
+#include "vm/BytecodeUtil.h"  // GET_JUMP_OFFSET, SET_JUMP_OFFSET, IsJumpOpcode
+
+using namespace js;
+using namespace js::frontend;
+
+void JumpList::push(jsbytecode* code, BytecodeOffset jumpOffset) {
+  if (!offset.valid()) {
+    SET_JUMP_OFFSET(&code[jumpOffset.value()], END_OF_LIST_DELTA);
+  } else {
+    SET_JUMP_OFFSET(&code[jumpOffset.value()], (offset - jumpOffset).value());
+  }
+  offset = jumpOffset;
+}
+
+void JumpList::patchAll(jsbytecode* code, JumpTarget target) {
+  if (!offset.valid()) {
+    // This list is not used. Nothing to do.
+    return;
+  }
+
+  BytecodeOffsetDiff delta;
+  BytecodeOffset jumpOffset = offset;
+  while (true) {
+    jsbytecode* pc = &code[jumpOffset.value()];
+    MOZ_ASSERT(IsJumpOpcode(JSOp(*pc)));
+    delta = BytecodeOffsetDiff(GET_JUMP_OFFSET(pc));
+    MOZ_ASSERT(delta.value() == END_OF_LIST_DELTA || delta.value() < 0);
+    BytecodeOffsetDiff span = target.offset - jumpOffset;
+    SET_JUMP_OFFSET(pc, span.value());
+
+    if (delta.value() == END_OF_LIST_DELTA) {
+      break;
+    }
+    jumpOffset += delta;
+  }
+}