Remove the fcontext field from all contexts.

Remove the fcontext field from all contexts.

Before: every context cached the nearest enclosing function context.  This
assumed that for nested contexts (i.e., with and catch contexts) the
enclosing function had a materialized link in the context chain.

Now: when necessary, we loop up the context chain to find such a context.
This enables catch contexts without forcing the enclosing function to
allocate its own context.

R=ager@chromium.org
BUG=
TEST=

Committed: http://code.google.com/p/v8/source/detail?r=8452

[Kevin Millikin (Chromium), 2011-06-28 14:37:47]

http://codereview.chromium.org/7230047/diff/1/src/arm/full-codegen-arm.cc
File src/arm/full-codegen-arm.cc (right):

http://codereview.chromium.org/7230047/diff/1/src/arm/full-codegen-arm.cc#new...
src/arm/full-codegen-arm.cc:1872: case Slot::CONTEXT:
Const initialization can be nested inside a with or catch, but with our current
semantics they are hoisted.

We could implement the loop up the context chain in generated code (even unroll
the loop once the chain length is known statically), but I've opted to just call
the runtime.

[fschneider, 2011-06-28 15:09:37]

LGTM.

[Mads Ager (chromium), 2011-06-29 05:56:27]

LGTM too

http://codereview.chromium.org/7230047/diff/1/src/arm/full-codegen-arm.cc
File src/arm/full-codegen-arm.cc (right):

http://codereview.chromium.org/7230047/diff/1/src/arm/full-codegen-arm.cc#new...
src/arm/full-codegen-arm.cc:1872: case Slot::CONTEXT:
On 2011/06/28 14:37:48, Kevin Millikin wrote:
> Const initialization can be nested inside a with or catch, but with our
current
> semantics they are hoisted.
> 
> We could implement the loop up the context chain in generated code (even
unroll
> the loop once the chain length is known statically), but I've opted to just
call
> the runtime.

Let's file a bug report (internal cleanup?) about investigating the impact of
native code implementation of this to not forget. Context stores could be quite
frequent and this would slow it down quite a bit.