Re-enable using push instructions for syncing the virtual frame....

Re-enable using push instructions for syncing the virtual frame.

This change fixes the problem with the original version of this approach
(r3032) that may lead to a corrupted stack if we would invoke spilling during 
syncing a large SMI constant (unsafe SMIs) in the virtual frame.

The new code for storing unsafe SMI constants does not use an extra temporary 
register. This prevents the compiler from ever having to spill during a 
virutal frame sync operation.

For storing a large SMI constant we previously generated:

  mov ecx, (large_smi & 0x0000ffff)
  xor ecx, (large_smi & 0xffff0000)
  push ecx

we now generate:

  push (large_smi & 0x0000ffff)
  or   [esp], (large_smi & 0xffff0000)

Not using a temporary register avoids spilling within an nvocation 
of VirtualFrame::SyncRange.


Committed: http://code.google.com/p/v8/source/detail?r=3313

[Kasper Lund, 2009-11-16 22:09:18]

LGTM, but you need to fix that name...

http://codereview.chromium.org/391079/diff/2003/3003
File src/ia32/codegen-ia32.h (right):

http://codereview.chromium.org/391079/diff/2003/3003#newcode474
Line 474: void LoadUnsafeSmi(int offset, Handle<Object> value);
This seems like pretty unfortunate overloading. Isn't it really more like
StoreUnsafeSmiInLocal?

[fschneider, 2009-11-16 23:08:37]

http://codereview.chromium.org/391079/diff/2003/3003
File src/ia32/codegen-ia32.h (right):

http://codereview.chromium.org/391079/diff/2003/3003#newcode474
Line 474: void LoadUnsafeSmi(int offset, Handle<Object> value);
On 2009/11/16 22:09:18, Kasper Lund wrote:
> This seems like pretty unfortunate overloading. Isn't it really more like
> StoreUnsafeSmiInLocal?

Done.