MIPS64: r6 compact branch optimization.

src/mips64/simulator-mips64.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 // Declares a Simulator for MIPS instructions if we are not generating a native
 // MIPS binary. This Simulator allows us to run and debug MIPS code generation
 // on regular desktop machines.
 // V8 calls into generated code by "calling" the CALL_GENERATED_CODE macro,
 // which will start execution in the Simulator or forwards to the real entry
@@ skipping 373 matching lines @@
     set_register(rd_reg, alu_out);
     TraceRegWr(alu_out);
   }
 
   void DecodeTypeImmediate(Instruction* instr);
   void DecodeTypeJump(Instruction* instr);
 
   // Used for breakpoints and traps.
   void SoftwareInterrupt(Instruction* instr);
 
+  // Compact branch guard.
+  void CheckForbiddenSlot(int64_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__,

[balazs.kilvady, 2015/12/18 19:18:05]

I think we should change the function name from 'IsForbiddenInBranchDelay' to
'IsForbiddenAfterBranch' on both 32 and 64 bits. What do you think?

[ivica.bogosavljevic, 2015/12/22 10:22:40]

Agree. Maybe we should have it IsForbiddenAfterBranchCompact if we are
performing the check on BranchCompact instructions.

[balazs.kilvady, 2015/12/22 11:01:56]

We can use the same function for r6 compact branches and for pre-r6 and r6 delay
slots so the 'Compact' word should not be added.

[ivica.bogosavljevic, 2015/12/22 12:23:41]

Acknowledged.

+               "Error: Unexpected instruction 0x%08x immediately after a "
+               "compact branch instruction.",
+               *reinterpret_cast<uint32_t*>(instr_aftter_compact_branch));
+    }
+  }
+
   // Stop helper functions.
   bool IsWatchpoint(uint64_t code);
   void PrintWatchpoint(uint64_t code);
   void HandleStop(uint64_t code, Instruction* instr);
   bool IsStopInstruction(Instruction* instr);
   bool IsEnabledStop(uint64_t code);
   void EnableStop(uint64_t code);
   void DisableStop(uint64_t code);
   void IncreaseStopCounter(uint64_t code);
   void PrintStopInfo(uint64_t code);
@@ skipping 133 matching lines @@
   static inline void UnregisterCTryCatch(Isolate* isolate) {
     Simulator::current(isolate)->PopAddress();
   }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // !defined(USE_SIMULATOR)
 #endif  // V8_MIPS_SIMULATOR_MIPS_H_