MIPS: port Avoid dynamic lookup when initializing let declared variables.

src/mips/full-codegen-mips.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1925 matching lines @@
         break;
     }
 
   } else if (var->mode() != Variable::CONST) {
     // Perform the assignment for non-const variables.  Const assignments
     // are simply skipped.
     Slot* slot = var->rewrite();
     switch (slot->type()) {
       case Slot::PARAMETER:
       case Slot::LOCAL:
+        if (FLAG_debug_code && op == Token::INIT_LET) {
+          // Check for an uninitialized let binding.
+          __ lw(a1, MemOperand(fp, SlotOffset(slot)));
+          __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
+          __ Check(eq, "Let binding re-initialization.", a1, Operand(t0));
+        }
         // Perform the assignment.
         __ sw(result_register(), MemOperand(fp, SlotOffset(slot)));
         break;
 
       case Slot::CONTEXT: {
         MemOperand target = EmitSlotSearch(slot, a1);
+        if (FLAG_debug_code && op == Token::INIT_LET) {
+          // Check for an uninitialized let binding.
+          __ lw(a3, target);
+          __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
+          __ Check(eq, "Let binding re-initialization.", a3, Operand(t0));
+        }
         // Perform the assignment and issue the write barrier.
         __ sw(result_register(), target);
         // RecordWrite may destroy all its register arguments.
         __ mov(a3, result_register());
          int offset = FixedArray::kHeaderSize + slot->index() * kPointerSize;
         __ RecordWrite(a1, Operand(offset), a2, a3);
         break;
       }
 
       case Slot::LOOKUP:
+        ASSERT(op != Token::INIT_LET);
         // Call the runtime for the assignment.
         __ push(v0);  // Value.
         __ li(a1, Operand(slot->var()->name()));
         __ li(a0, Operand(Smi::FromInt(strict_mode_flag())));
         __ Push(cp, a1, a0);  // Context, name, strict mode.
         __ CallRuntime(Runtime::kStoreContextSlot, 4);
         break;
 
       case Slot::GLOBAL:
         UNREACHABLE();
@@ skipping 2354 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS