Fix the stack limits setting API so it is usable.

src/execution.cc

Index: src/execution.cc
===================================================================
--- src/execution.cc	(revision 2982)
+++ src/execution.cc	(working copy)
@@ -61,9 +61,6 @@
   // Entering JavaScript.
   VMState state(JS);
 
-  // Guard the stack against too much recursion.
-  StackGuard guard;
-
   // Placeholder for return value.
   Object* value = reinterpret_cast<Object*>(kZapValue);
 
@@ -217,55 +214,6 @@
 StackGuard::ThreadLocal StackGuard::thread_local_;
 
 
-StackGuard::StackGuard() {
-  // NOTE: Overall the StackGuard code assumes that the stack grows towards
-  // lower addresses.
-  ExecutionAccess access;
-  if (thread_local_.nesting_++ == 0) {
-    // Initial StackGuard is being set. We will set the stack limits based on
-    // the current stack pointer allowing the stack to grow kLimitSize from
-    // here.
-
-    // Ensure that either the stack limits are unset (kIllegalLimit) or that
-    // they indicate a pending interruption. The interrupt limit will be
-    // temporarily reset through the code below and reestablished if the
-    // interrupt flags indicate that an interrupt is pending.
-    ASSERT(thread_local_.jslimit_ == kIllegalLimit ||
-           (thread_local_.jslimit_ == kInterruptLimit &&
-            thread_local_.interrupt_flags_ != 0));
-    ASSERT(thread_local_.climit_ == kIllegalLimit ||
-           (thread_local_.climit_ == kInterruptLimit &&
-            thread_local_.interrupt_flags_ != 0));
-
-    uintptr_t limit = GENERATED_CODE_STACK_LIMIT(kLimitSize);
-    thread_local_.initial_jslimit_ = thread_local_.jslimit_ = limit;
-    Heap::SetStackLimit(limit);
-    // NOTE: The check for overflow is not safe as there is no guarantee that
-    // the running thread has its stack in all memory up to address 0x00000000.
-    thread_local_.initial_climit_ = thread_local_.climit_ =
-        reinterpret_cast<uintptr_t>(this) >= kLimitSize ?
-            reinterpret_cast<uintptr_t>(this) - kLimitSize : 0;
-
-    if (thread_local_.interrupt_flags_ != 0) {
-      set_limits(kInterruptLimit, access);
-    }
-  }
-  // Ensure that proper limits have been set.
-  ASSERT(thread_local_.jslimit_ != kIllegalLimit &&
-         thread_local_.climit_ != kIllegalLimit);
-  ASSERT(thread_local_.initial_jslimit_ != kIllegalLimit &&
-         thread_local_.initial_climit_ != kIllegalLimit);
-}
-
-
-StackGuard::~StackGuard() {
-  ExecutionAccess access;
-  if (--thread_local_.nesting_ == 0) {
-    set_limits(kIllegalLimit, access);
-  }
-}
-
-
 bool StackGuard::IsStackOverflow() {
   ExecutionAccess access;
   return (thread_local_.jslimit_ != kInterruptLimit &&
@@ -285,15 +233,16 @@
   ExecutionAccess access;
   // If the current limits are special (eg due to a pending interrupt) then
   // leave them alone.
+  uintptr_t jslimit = SimulatorStack::JsLimitFromCLimit(limit);
   if (thread_local_.jslimit_ == thread_local_.initial_jslimit_) {
-    thread_local_.jslimit_ = limit;
-    Heap::SetStackLimit(limit);
+    thread_local_.jslimit_ = jslimit;
+    Heap::SetStackLimit(jslimit);
   }
   if (thread_local_.climit_ == thread_local_.initial_climit_) {
     thread_local_.climit_ = limit;
   }
   thread_local_.initial_climit_ = limit;
-  thread_local_.initial_jslimit_ = limit;
+  thread_local_.initial_jslimit_ = jslimit;
 }
 
 
@@ -407,10 +356,61 @@
 }
 
 
+static internal::Thread::LocalStorageKey stack_limit_key =
+    internal::Thread::CreateThreadLocalKey();
+
+
 void StackGuard::FreeThreadResources() {
+  Thread::SetThreadLocal(
+      stack_limit_key,
+      reinterpret_cast<void*>(thread_local_.initial_climit_));
 }
 
 
+void StackGuard::ThreadLocal::Clear() {
+  initial_jslimit_ = kIllegalLimit;
+  jslimit_ = kIllegalLimit;
+  initial_climit_ = kIllegalLimit;
+  climit_ = kIllegalLimit;
+  nesting_ = 0;
+  postpone_interrupts_nesting_ = 0;
+  interrupt_flags_ = 0;
+  Heap::SetStackLimit(kIllegalLimit);
+}
+
+
+void StackGuard::ThreadLocal::Initialize() {
+  if (initial_climit_ == kIllegalLimit) {
+    // Takes the address of the limit variable in order to find out where
+    // the top of stack is right now.
+    intptr_t limit = reinterpret_cast<intptr_t>(&limit) - kLimitSize;
+    initial_jslimit_ = SimulatorStack::JsLimitFromCLimit(limit);
+    jslimit_ = SimulatorStack::JsLimitFromCLimit(limit);
+    initial_climit_ = limit;
+    climit_ = limit;
+    Heap::SetStackLimit(SimulatorStack::JsLimitFromCLimit(limit));
+  }
+  nesting_ = 0;
+  postpone_interrupts_nesting_ = 0;
+  interrupt_flags_ = 0;
+}
+
+
+void StackGuard::ClearThread(const ExecutionAccess& lock) {
+  thread_local_.Clear();
+}
+
+
+void StackGuard::InitThread(const ExecutionAccess& lock) {
+  thread_local_.Initialize();
+  void* stored_limit = Thread::GetThreadLocal(stack_limit_key);
+  // You should hold the ExecutionAccess lock when you call this.
+  if (stored_limit != NULL) {
+    StackGuard::SetStackLimit(reinterpret_cast<intptr_t>(stored_limit));
+  }
+}
+
+
 // --- C a l l s   t o   n a t i v e s ---
 
 #define RETURN_NATIVE_CALL(name, argc, argv, has_pending_exception) \