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

src/mips/constants-mips.h

Index: src/mips/constants-mips.h
diff --git a/src/mips/constants-mips.h b/src/mips/constants-mips.h
index 25673301331a312c03a9d7de9134efc23e40b944..cb9d429f32389b57ee0ede045554680c4e13b8a6 100644
--- a/src/mips/constants-mips.h
+++ b/src/mips/constants-mips.h
@@ -158,6 +158,18 @@ enum SoftwareInterruptCodes {
   call_rt_redirected = 0xfffff
 };
 
+// On MIPS Simulator breakpoints can have different codes:
+// - Breaks between 0 and kMaxWatchpointCode are treated as simple watchpoints,
+//   the simulator will run through them and print the registers.
+// - Breaks between kMaxWatchpointCode and kMaxStopCode are treated as stop()
+//   instructions (see Assembler::stop()).
+// - Breaks larger than kMaxStopCode are simple breaks, dropping you into the
+//   debugger.
+static const uint32_t kMaxWatchpointCode = 31;
+static const uint32_t kMaxStopCode = 127;
+STATIC_ASSERT(kMaxWatchpointCode < kMaxStopCode);
+
+
 // ----- Fields offset and length.
 static const int kOpcodeShift   = 26;
 static const int kOpcodeBits    = 6;