Remove spills from complex assignments. Some compound assignments now...

Remove spills from complex assignments.  Some compound assignments now
invalidate the target variable's slot while the right-hand-side is
evaluated.

[Kevin Millikin (Chromium), 2009-02-03 09:48:55]

LGTM with some small comments.

http://codereview.chromium.org/19706/diff/1/3
File src/codegen-ia32.cc (right):

http://codereview.chromium.org/19706/diff/1/3#newcode3145
Line 3145: //      VirtualFrame::SpilledScope spilled_scope(this);
Remove code rather than commenting it out.

http://codereview.chromium.org/19706/diff/1/3#newcode3148
Line 3148: if (literal != NULL || (right_var != NULL && right_var != var)) {
This needs a simple comment saying what you are doing and why.

http://codereview.chromium.org/19706/diff/1/2
File src/virtual-frame-ia32.cc (right):

http://codereview.chromium.org/19706/diff/1/2#newcode173
Line 173: if (elements_[index].is_valid()) {
I think there should also be an early exit in RawSyncElementAt for invalid
elements.

[William Hesse, 2009-02-04 14:07:54]

All comments addressed.  Committed as change 1226.