Omit redundant smi checks in write barriers.

src/ia32/lithium-codegen-ia32.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 4271 matching lines @@
       __ mov(operand, Immediate(ToInteger32(operand_value)));
     } else {
       Register value = ToRegister(instr->value());
       __ Store(value, operand, representation);
     }
     return;
   }
 
   Register object = ToRegister(instr->object());
   Handle<Map> transition = instr->transition();
+  SmiCheck check_needed =
+      instr->hydrogen()->value()->IsHeapObject()
+          ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
 
   if (FLAG_track_fields && representation.IsSmi()) {
     if (instr->value()->IsConstantOperand()) {
       LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
       if (!IsSmi(operand_value)) {
         DeoptimizeIf(no_condition, instr->environment());
       }
     }
   } else if (FLAG_track_heap_object_fields && representation.IsHeapObject()) {
     if (instr->value()->IsConstantOperand()) {
       LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
       if (IsInteger32(operand_value)) {
         DeoptimizeIf(no_condition, instr->environment());
       }
     } else {
       if (!instr->hydrogen()->value()->type().IsHeapObject()) {
         Register value = ToRegister(instr->value());
         __ test(value, Immediate(kSmiTagMask));
         DeoptimizeIf(zero, instr->environment());
+
+        // We know that value is a smi now, 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());
     if (CpuFeatures::IsSupported(SSE2)) {
       CpuFeatureScope scope(masm(), SSE2);
       XMMRegister value = ToDoubleRegister(instr->value());
       __ movsd(FieldOperand(object, offset), value);
@@ skipping 17 matching lines @@
                           HeapObject::kMapOffset,
                           temp_map,
                           temp,
                           GetSaveFPRegsMode(),
                           OMIT_REMEMBERED_SET,
                           OMIT_SMI_CHECK);
     }
   }
 
   // Do the store.
-  SmiCheck check_needed =
-      instr->hydrogen()->value()->IsHeapObject()
-          ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
-
   Register write_register = object;
   if (!access.IsInobject()) {
     write_register = ToRegister(instr->temp());
     __ mov(write_register, FieldOperand(object, JSObject::kPropertiesOffset));
   }
 
   MemOperand operand = FieldOperand(write_register, offset);
   if (instr->value()->IsConstantOperand()) {
     LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
     if (operand_value->IsRegister()) {
@@ skipping 1904 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32