Reland "Track field types.".

src/arm/lithium-codegen-arm.cc

 // Copyright 2012 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 4093 matching lines @@
 
   ASSERT(!(representation.IsSmi() &&
            instr->value()->IsConstantOperand() &&
            !IsSmi(LConstantOperand::cast(instr->value()))));
   if (representation.IsHeapObject()) {
     Register value = ToRegister(instr->value());
     if (!instr->hydrogen()->value()->type().IsHeapObject()) {
       __ SmiTst(value);
       DeoptimizeIf(eq, 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(!instr->hydrogen()->NeedsWriteBarrier());
     DwVfpRegister value = ToDoubleRegister(instr->value());
     __ vstr(value, FieldMemOperand(object, offset));
     return;
   }
@@ skipping 1739 matching lines @@
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal