[turbofan] First step towards sanitizing for-in and making it optimizable.

src/mips/full-codegen-mips.cc

 // Copyright 2012 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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS
 
 // Note on Mips implementation:
 //
@@ skipping 1241 matching lines @@
 
   // For proxies, no filtering is done.
   // TODO(rossberg): What if only a prototype is a proxy? Not specified yet.
   DCHECK_EQ(static_cast<Smi*>(0), Smi::FromInt(0));
   __ Branch(&update_each, eq, a2, Operand(zero_reg));
 
   // Convert the entry to a string or (smi) 0 if it isn't a property
   // any more. If the property has been removed while iterating, we
   // just skip it.
   __ Push(a1, a3);  // Enumerable and current entry.
-  __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION);
+  __ CallRuntime(Runtime::kForInFilter, 2);
   PrepareForBailoutForId(stmt->FilterId(), TOS_REG);
   __ mov(a3, result_register());
-  __ Branch(loop_statement.continue_label(), eq, a3, Operand(zero_reg));
+  __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
+  __ Branch(loop_statement.continue_label(), eq, a3, Operand(at));
 
   // Update the 'each' property or variable from the possibly filtered
   // entry in register a3.
   __ bind(&update_each);
   __ mov(result_register(), a3);
   // Perform the assignment as if via '='.
   { EffectContext context(this);
     EmitAssignment(stmt->each(), stmt->EachFeedbackSlot());
     PrepareForBailoutForId(stmt->AssignmentId(), NO_REGISTERS);
   }
@@ skipping 4241 matching lines @@
       Assembler::target_address_at(pc_immediate_load_address)) ==
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS