MIPS: r6 compact branch optimization.

src/mips/simulator-mips.h

Index: src/mips/simulator-mips.h
diff --git a/src/mips/simulator-mips.h b/src/mips/simulator-mips.h
index 796d08fc2700c351465ac26635a1df8fbd231b27..624d4acf8094936fbce5b2ad08eb9a3afe3af18d 100644
--- a/src/mips/simulator-mips.h
+++ b/src/mips/simulator-mips.h
@@ -315,6 +315,7 @@ class Simulator {
   void DecodeTypeRegisterLRsType();
 
   Instruction* currentInstr_;
+
   inline Instruction* get_instr() const { return currentInstr_; }
   inline void set_instr(Instruction* instr) { currentInstr_ = instr; }
 
@@ -346,6 +347,18 @@ class Simulator {
   // Used for breakpoints and traps.
   void SoftwareInterrupt(Instruction* instr);
 
+  // Compact branch guard.
+  void CheckForbiddenSlot(int32_t current_pc) {
+    Instruction* instr_aftter_compact_branch =
+        reinterpret_cast<Instruction*>(current_pc + Instruction::kInstrSize);
+    if (instr_aftter_compact_branch->IsForbiddenInBranchDelay()) {
+      V8_Fatal(__FILE__, __LINE__,
+               "Error: Unexpected instruction 0x%08x immediately after a "
+               "compact branch instruction.",
+               *reinterpret_cast<uint32_t*>(instr_aftter_compact_branch));
+    }
+  }
+
   // Stop helper functions.
   bool IsWatchpoint(uint32_t code);
   void PrintWatchpoint(uint32_t code);