Infer whether a variable is assigned

Infer whether a variable is assigned in inner functions

R=titzer@chromium.org
BUG=

Committed: https://code.google.com/p/v8/source/detail?r=22039

[titzer, 2014-06-23 13:03:19]

https://codereview.chromium.org/345573002/diff/1/src/variables.h
File src/variables.h (right):

https://codereview.chromium.org/345573002/diff/1/src/variables.h#newcode84
src/variables.h:84: bool is_assigned_in_inner_function() {
may_be_assigned_in_inner_function() ?

https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc
File test/cctest/test-parsing.cc (right):

https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc#...
test/cctest/test-parsing.cc:2615:
factory->NewStringFromUtf8(i::CStrVector("x")).ToHandleChecked();
factory->InternalizeUtf8String()?

[titzer, 2014-06-23 13:04:23]

On 2014/06/23 13:03:19, titzer wrote:
> https://codereview.chromium.org/345573002/diff/1/src/variables.h
> File src/variables.h (right):
> 
> https://codereview.chromium.org/345573002/diff/1/src/variables.h#newcode84
> src/variables.h:84: bool is_assigned_in_inner_function() {
> may_be_assigned_in_inner_function() ?

Actually maybe we want is_not_assigned_in_inner_function(), i.e. the inverse?

> https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc
> File test/cctest/test-parsing.cc (right):
> 
>
https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc#...
> test/cctest/test-parsing.cc:2615:
> factory->NewStringFromUtf8(i::CStrVector("x")).ToHandleChecked();
> factory->InternalizeUtf8String()?

[rossberg, 2014-06-24 13:40:43]

Refined the analysis to work for the general case, not just inner function uses.
However, it's conservative, and marks some stupid cases as possibly-assigned
(e.g., "var x; var x;"). See the test cases.

https://codereview.chromium.org/345573002/diff/1/src/variables.h
File src/variables.h (right):

https://codereview.chromium.org/345573002/diff/1/src/variables.h#newcode84
src/variables.h:84: bool is_assigned_in_inner_function() {
On 2014/06/23 13:03:19, titzer wrote:
> may_be_assigned_in_inner_function() ?

Done.

https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc
File test/cctest/test-parsing.cc (right):

https://codereview.chromium.org/345573002/diff/1/test/cctest/test-parsing.cc#...
test/cctest/test-parsing.cc:2615:
factory->NewStringFromUtf8(i::CStrVector("x")).ToHandleChecked();
On 2014/06/23 13:03:19, titzer wrote:
> factory->InternalizeUtf8String()?

Done (also below).

[titzer, 2014-06-25 12:33:47]

lgtm

[rossberg, 2014-06-26 12:00:15]

Committed patchset #3 manually as r22039.