Fix for issue 6359 - Make snapshots platform independent.

Fix for issue 6359 - Make snapshots platform independent.
The issue previously was that an instance size was stored a
size in bytes, similarly field offsets were stored as an offset
in bytes. This caused issues when generating the snapshot on
one platform and reading it on another platform.
The VM has been changed to store the instance size as a size in
words and the field offset as an offset in words.
Committed: https://code.google.com/p/dart/source/detail?r=15538

[srdjan, 2012-11-29 00:49:22]

LGTM after clarifying the left/right shift on signed values.

https://codereview.chromium.org/11421117/diff/2003/vm/snapshot.cc
File vm/snapshot.cc (right):

https://codereview.chromium.org/11421117/diff/2003/vm/snapshot.cc#newcode1038
vm/snapshot.cc:1038: const intptr_t kBits = 62;
Should this be kMintBits, defined at similar place as kSmiBits?

https://codereview.chromium.org/11421117/diff/2003/vm/snapshot.cc#newcode1040
vm/snapshot.cc:1040: const int64_t kMin = -(static_cast<int64_t>(1) << kBits);
ditto for min and max (see class Smi).

[siva, 2012-11-29 03:08:20]

Changed shift operations to mul/div.

https://codereview.chromium.org/11421117/diff/2003/vm/snapshot.cc
File vm/snapshot.cc (right):

https://codereview.chromium.org/11421117/diff/2003/vm/snapshot.cc#newcode1038
vm/snapshot.cc:1038: const intptr_t kBits = 62;
Strictly speaking this not kMintBits as you represent
full 64 bit values as Mint values. These are more
SmiBits for 64 bit architectures.

I could rename them to kSmi64Bits and leave them here.

On 2012/11/29 00:49:22, srdjan wrote:
> Should this be kMintBits, defined at similar place as kSmiBits?