[tools] add lldbinit

The goal of this commit is to add the equivalent to gdbinit but
for lldb. I've tried to replicate the commands as close as possible
but I'm unsure about the jss command and hoping to get some feedback
on it in addition to the bta command which I'm not sure how/when this
could be used. This is probably just inexperience on my part.

The lldbinit file can be placed into a directory prefixed with dot
(.lldbinit) and the python script is currently expected to be in the
same directory. The path to the script can be changed manually if needed
as well.

NOTRY=true

Review-Url: https://codereview.chromium.org/2758373002
Cr-Commit-Position: refs/heads/master@{#44136}

tools/lldb_commands.py

+# Copyright 2017 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import lldb
+import re
+
+def jst(debugger, *args):
+  """Print the current JavaScript stack trace"""
+  target = debugger.GetSelectedTarget()
+  process = target.GetProcess()
+  thread = process.GetSelectedThread()
+  frame = thread.GetSelectedFrame()
+  frame.EvaluateExpression("_v8_internal_Print_StackTrace();")
+  print("")
+
+def jss(debugger, *args):
+  """Skip the jitted stack on x64 to where we entered JS last"""
+  target = debugger.GetSelectedTarget()
+  process = target.GetProcess()
+  thread = process.GetSelectedThread()
+  frame = thread.GetSelectedFrame()
+  js_entry_sp = frame.EvaluateExpression(
+      "v8::internal::Isolate::Current()->thread_local_top()->js_entry_sp_;") \
+       .GetValue()
+  sizeof_void = frame.EvaluateExpression("sizeof(void*)").GetValue()
+  rbp = frame.FindRegister("rbp")
+  rsp = frame.FindRegister("rsp")
+  pc = frame.FindRegister("pc")
+  rbp = js_entry_sp
+  rsp = js_entry_sp + 2 *sizeof_void
+  pc.value = js_entry_sp + sizeof_void
+
+def bta(debugger, *args):
+  """Print stack trace with assertion scopes"""
+  func_name_re = re.compile("([^(<]+)(?:\(.+\))?")
+  assert_re = re.compile(
+      "^v8::internal::Per\w+AssertType::(\w+)_ASSERT, (false|true)>")
+  target = debugger.GetSelectedTarget()
+  process = target.GetProcess()
+  thread = process.GetSelectedThread()
+  frame = thread.GetSelectedFrame()
+  for frame in thread:
+    functionSignature = frame.GetDisplayFunctionName()
+    if functionSignature is None:
+      continue
+    functionName = func_name_re.match(functionSignature)
+    line = frame.GetLineEntry().GetLine()
+    sourceFile = frame.GetLineEntry().GetFileSpec().GetFilename()
+    if line:
+      sourceFile = sourceFile + ":" + str(line)
+
+    if sourceFile is None:
+      sourceFile = ""
+    print("[%-2s] %-60s %-40s" % (frame.GetFrameID(),
+                                  functionName.group(1),
+                                  sourceFile))
+    match = assert_re.match(str(functionSignature))
+    if match:
+      if match.group(3) == "false":
+        prefix = "Disallow"
+        color = "\033[91m"
+      else:
+        prefix = "Allow"
+        color = "\033[92m"
+      print("%s -> %s %s (%s)\033[0m" % (
+          color, prefix, match.group(2), match.group(1)))
+
+def __lldb_init_module (debugger, dict):
+  debugger.HandleCommand('command script add -f lldb_commands.jst jst')
+  debugger.HandleCommand('command script add -f lldb_commands.jss jss')
+  debugger.HandleCommand('command script add -f lldb_commands.bta bta')

tools/lldbinit

+# Copyright 2017 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Print HeapObjects.
+command regex -h 'Print a v8 JavaScript object' job 's/(.+)/expr -- '_v8_internal_Print_Object((void*)(%1))/'
+
+# Print v8::Local handle value.
+command regex -h 'Print content of a v8::Local handle' jlh 's/(.+)/expr -- '_v8_internal_Print_Object(*(v8::internal::Object**)(*%1))/'
+
+# Print Code objects containing given PC.
+command regex -h 'Print a v8 Code object from an internal code address' jco 's/(.+)/expr -- '_v8_internal_Print_Code((void*)(*%1))/'
+
+# Print FeedbackVector
+command regex -h 'Print a v8 FeedbackVector object' jfv 's/(.+)/expr -- '_v8_internal_Print_FeedbackVector((void*)(%1))/'
+
+# Print FeedbackMetadata
+command regex -h 'Print a v8 FeedbackMetadata object' jfm 's/(.+)/expr -- '_v8_internal_Print_FeedbackMetadata((void*)(%1))/'
+
+# Print DescriptorArray.
+command regex -h 'Print a v8 DescriptorArray object' jda 's/(.+)/expr -- '_v8_internal_Print_DescriptorArray((void*)(%1))/'
+
+# Print LayoutDescriptor.
+command regex -h 'Print a v8 LayoutDescriptor object' jld 's/(.+)/expr -- '_v8_internal_Print_LayoutDescriptor((void*)(%1))/'
+
+# Print TransitionArray.
+command regex -h 'Print a v8 TransitionArray object' jta 's/(.+)/expr -- '_v8_internal_Print_TransitionArray((void*)(%1))/'
+
+command script import ~/lldb_commands.py