Add "has fast elements" bit to maps and use it in inlined keyed loads.

Add "has fast elements" bit to maps and use it in inlined keyed loads.

A potential issue with this change is creating lots of maps when
objects flip between fast/slow elements modes.  We could add special
transitions to avoid this.  Yet testing this on our benchmarks, gmail,
and wave seems to indicate that this is not a real problem.

Committed: http://code.google.com/p/v8/source/detail?r=4941

[Mads Ager (chromium), 2010-06-24 09:22:17]

LGTM

http://codereview.chromium.org/2870018/diff/2001/3014
File src/objects.h (right):

http://codereview.chromium.org/2870018/diff/2001/3014#newcode3027
src/objects.h:3027: // Returns a copy of the map, with all transitions dropped
from the
Please update these comments to state that a copy is only created if the map is
not already the fast/slow map. Reading this comment it seems safe to use this to
copy a map and change it.

[Vitaly Repeshko, 2010-06-24 13:58:55]

I also added nop padding to the Abort macro on ARM to make its size constant (as
discussed with Erik). This is required to make patching of the inlined keyed
load code work.

http://codereview.chromium.org/2870018/diff/2001/3014
File src/objects.h (right):

http://codereview.chromium.org/2870018/diff/2001/3014#newcode3027
src/objects.h:3027: // Returns a copy of the map, with all transitions dropped
from the
On 2010/06/24 09:22:17, Mads Ager wrote:
> Please update these comments to state that a copy is only created if the map
is
> not already the fast/slow map. Reading this comment it seems safe to use this
to
> copy a map and change it.

Done.