Initialize tags back to 0 before using it.

vm/object.cc

Index: vm/object.cc
===================================================================
--- vm/object.cc	(revision 6666)
+++ vm/object.cc	(working copy)
@@ -6126,12 +6126,12 @@
 
 
 void ICData::set_function(const Function& value) const {
-  raw_ptr()->function_ = value.raw();
+  StorePointer(&raw_ptr()->function_, value.raw());
 }
 
 
 void ICData::set_target_name(const String& value) const {
-  raw_ptr()->target_name_ = value.raw();
+  StorePointer(&raw_ptr()->target_name_, value.raw());
 }
 
 
@@ -6146,7 +6146,7 @@
 
 
 void ICData::set_ic_data(const Array& value) const {
-  raw_ptr()->ic_data_ = value.raw();
+  StorePointer(&raw_ptr()->ic_data_, value.raw());
 }
 
 
@@ -8536,6 +8536,7 @@
     intptr_t leftover_size = capacity_size - used_size;
 
     uword addr = RawObject::ToAddr(array.raw()) + used_size;
+    tags = 0;

[cshapiro, 2012/04/18 20:52:00]

This seems like a strange idiom but I may not understand what is actually going
on.  Rather than doing this

  tag = 0
  tag = DoSomething(tag)
  raw->ptr()->tags_ = tags

Why not just do

  uword tag = DoSomething(0)
  raw->ptr()->tags_ = tag

It was unclear to me what the effect of the tags = 0 assignment was when I
looked at this code.  Keeping the def and use as close together as possible
would be great.

[siva, 2012/04/18 21:21:17]

This is in preparation for merging the tags fields and the header field into one
word.

The pattern at that point will look as:

header_bits = 0;
header_bits = UpdateTag info...
header_bits = UpdateSize...
header_bits = UpdateClassId ...
raw->ptr()->header_ = header_bits;


On 2012/04/18 20:52:00, cshapiro wrote:

     if (leftover_size >= Array::InstanceSize(0)) {
       // As we have enough space to use an array object, update the leftover
       // space as an Array object.