Allow forcing the use of a simulator from the build script

independently of the host architecture.

Fix build issue for the mips simulator.  The mips simulator does not
currently work, but at least this change does not make it worse.

Review URL: http://codereview.chromium.org/4090003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5701 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/globals.h

@@ -94,12 +94,16 @@ namespace internal {
 #endif
 
 // Determine whether we are running in a simulated environment.
+// Setting USE_SIMULATOR explicitly from the build script will force
+// the use of a simulated environment.
+#if !defined(USE_SIMULATOR)
 #if (defined(V8_TARGET_ARCH_ARM) && !defined(V8_HOST_ARCH_ARM))
 #define USE_SIMULATOR 1
 #endif
 #if (defined(V8_TARGET_ARCH_MIPS) && !defined(V8_HOST_ARCH_MIPS))
 #define USE_SIMULATOR 1
 #endif
+#endif
 
 // Define unaligned read for the target architectures supporting it.
 #if defined(V8_TARGET_ARCH_X64) || defined(V8_TARGET_ARCH_IA32)

src/top.cc

@@ -67,8 +67,12 @@ void ThreadLocalTop::Initialize() {
   c_entry_fp_ = 0;
   handler_ = 0;
 #ifdef USE_SIMULATOR
+#ifdef V8_TARGET_ARCH_ARM
   simulator_ = assembler::arm::Simulator::current();
-#endif  // USE_SIMULATOR
+#elif V8_TARGET_ARCH_MIPS
+  simulator_ = assembler::mips::Simulator::current();
+#endif
+#endif
 #ifdef ENABLE_LOGGING_AND_PROFILING
   js_entry_sp_ = 0;
 #endif
@@ -1066,7 +1070,11 @@ char* Top::RestoreThread(char* from) {
   // This might be just paranoia, but it seems to be needed in case a
   // thread_local_ is restored on a separate OS thread.
 #ifdef USE_SIMULATOR
+#ifdef V8_TARGET_ARCH_ARM
   thread_local_.simulator_ = assembler::arm::Simulator::current();
+#elif V8_TARGET_ARCH_MIPS
+  thread_local_.simulator_ = assembler::mips::Simulator::current();
+#endif
 #endif
   return from + sizeof(thread_local_);
 }

src/v8.cc

@@ -69,7 +69,11 @@ bool V8::Initialize(Deserializer* des) {
 
   // Initialize other runtime facilities
 #if defined(USE_SIMULATOR)
+#if defined(V8_TARGET_ARCH_ARM)
   ::assembler::arm::Simulator::Initialize();
+#elif defined(V8_TARGET_ARCH_MIPS)
+  ::assembler::mips::Simulator::Initialize();
+#endif
 #endif
 
   { // NOLINT