MIPS: Added the stop() instruction with same behavior as on Arm simulator.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 2e10904cb1aa8724618491861fad37bcc8197cf5..6763b7976ed5547ac6ddd114a157ae0e4bf23838 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -1336,13 +1336,37 @@ void Assembler::lui(Register rd, int32_t j) {
 //-------------Misc-instructions--------------
 
 // Break / Trap instructions.
-void Assembler::break_(uint32_t code) {
+void Assembler::break_(uint32_t code, bool break_as_stop) {
   ASSERT((code & ~0xfffff) == 0);
+  // We need to invalidate breaks that could be stops as well because the
+  // simulator expects a char pointer after the stop instruction.
+  // See constants-mips.h for explanation.
+  ASSERT((break_as_stop &&
+          code <= kMaxStopCode &&
+          code > kMaxWatchpointCode) ||
+         (!break_as_stop &&
+          (code > kMaxStopCode ||
+           code <= kMaxWatchpointCode)));
   Instr break_instr = SPECIAL | BREAK | (code << 6);
   emit(break_instr);
 }
 
 
+void Assembler::stop(const char* msg, uint32_t code) {
+  ASSERT(code > kMaxWatchpointCode);
+  ASSERT(code <= kMaxStopCode);
+#if defined(V8_HOST_ARCH_MIPS)
+  break_(0x54321);
+#else  // V8_HOST_ARCH_MIPS
+  BlockTrampolinePoolFor(2);
+  // The Simulator will handle the stop instruction and get the message address.
+  // On MIPS stop() is just a special kind of break_().
+  break_(code, true);
+  emit(reinterpret_cast<Instr>(msg));
+#endif
+}
+
+
 void Assembler::tge(Register rs, Register rt, uint16_t code) {
   ASSERT(is_uint10(code));
   Instr instr = SPECIAL | TGE | rs.code() << kRsShift