Reland "Track field types.".

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 4019 matching lines @@
       LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
       if (chunk_->LookupConstant(operand_value)->HasSmiValue()) {
         DeoptimizeIf(no_condition, instr->environment());
       }
     } else {
       if (!hinstr->value()->type().IsHeapObject()) {
         Register value = ToRegister(instr->value());
         Condition cc = masm()->CheckSmi(value);
         DeoptimizeIf(cc, instr->environment());
 
-        // We know that value is a smi now, so we can omit the check below.
+        // We know now that value is not a smi, so we can omit the check below.
         check_needed = OMIT_SMI_CHECK;
       }
     }
   } else if (representation.IsDouble()) {
     ASSERT(transition.is_null());
     ASSERT(access.IsInobject());
     ASSERT(!hinstr->NeedsWriteBarrier());
     XMMRegister value = ToDoubleRegister(instr->value());
     __ movsd(FieldOperand(object, offset), value);
     return;
@@ skipping 1673 matching lines @@
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64