Give a length field to stack bitmaps.

Give a length field to stack bitmaps.

The bitmaps describing the stack have an explicit length field.  It is now
an assertion failure to read bits outside the length --- they are no longer
assumed to be false.

Also remove an unused method and simplify the implementation of
BitmapBuilder by removing an embedded member that was always referred to via
a pointer.

R=vegorov@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=11138

[Kevin Millikin (Google), 2012-08-21 13:24:07]

http://codereview.chromium.org/10832410/diff/1/runtime/vm/code_descriptors.cc
File runtime/vm/code_descriptors.cc (right):

http://codereview.chromium.org/10832410/diff/1/runtime/vm/code_descriptors.cc...
runtime/vm/code_descriptors.cc:57: bitmap->SetLength(entry_length_);
Long-term, we will not set the length here but earlier (in the register
allocator?) when we finish the bitmap.

[Vyacheslav Egorov (Google), 2012-08-22 11:49:40]

lgtm

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/bitmap.h
File runtime/vm/bitmap.h (right):

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/bitmap.h#ne...
runtime/vm/bitmap.h:63: intptr_t size_in_bytes_;
I would rename size_in_bytes_ and bit_list_ in such a way that connection
between them would become apparent. 

I would also add a comment here that reading bits outside of backing store is
allowed and they are assumed to be false.

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/code_descri...
File runtime/vm/code_descriptors.cc (right):

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/code_descri...
runtime/vm/code_descriptors.cc:57: bitmap->SetLength(entry_length_);
On 2012/08/21 13:24:07, kmillikin wrote:
> Long-term, we will not set the length here but earlier (in the register
> allocator?) when we finish the bitmap.

Add a TODO

[Kevin Millikin (Google), 2012-08-22 11:56:27]

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/bitmap.h
File runtime/vm/bitmap.h (right):

https://chromiumcodereview.appspot.com/10832410/diff/1/runtime/vm/bitmap.h#ne...
runtime/vm/bitmap.h:63: intptr_t size_in_bytes_;
On 2012/08/22 11:49:40, Vyacheslav Egorov (Google) wrote:
> I would rename size_in_bytes_ and bit_list_ in such a way that connection
> between them would become apparent. 
> 
> I would also add a comment here that reading bits outside of backing store is
> allowed and they are assumed to be false.

OK.  (bit_list_, size_in_bytes_) => (data_, data_size_in_bytes_).