Implement simple effect typing for variables

Implement simple effect typing for variables

For that, we maintain an abstract store typing of all variables with LOCAL location (i.e., those that do not escape the function's own scope). We treat assignments as sequential effects that modify this store.

When control flow branches, we have to compute the disjunction of possible effects. To that end, we represent the store as a stack of effect sets, such that we can cheaply push and pop "local" effects when control flow has to branch.

In cases of non-local control transfer from an unknown source, we currently erase all knowledge about the store.

The 'switch' statement is still to come.

For a formulation of the typing rules, see:

https://docs.google.com/a/google.com/file/d/0B3wuXSv9YKuKeUNkVXZDemZ0Z1E

;)

R=jkummerow@chromium.org
BUG=

Committed: http://code.google.com/p/v8/source/detail?r=15776

[titzer, 2013-07-11 16:48:46]

Where is this mythical src/effects.h?

[Jakob Kummerow, 2013-07-19 12:09:03]

LGTM with nits.

https://codereview.chromium.org/19054006/diff/13001/src/effects.h
File src/effects.h (right):

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode122
src/effects.h:122: effect = Effect::Seq(locator.value(), effect,
Base::isolate());
nit: {} please

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode135
src/effects.h:135: effect = Effect::Alt(locator.value(), effect,
Base::isolate());
nit: {} please

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode216
src/effects.h:216: typedef ZoneSplayTree<SplayTreeConfig> Map;
We already have a v8::internal::Map. Please use another name here. EffectsMap?

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode248
src/effects.h:248: explicit Effects(Zone* zone) :
nit: ':' goes on the next line. Line break suggestion:

  explicit Effects(Zone* zone)
      : EffectsMixin<Var,
                     EffectsBase<Var, kNoVar>,
                     Effects<Var, kNoVar> >(zone) {}

[rossberg, 2013-07-19 12:54:36]

Committed patchset #3 manually as r15776 (presubmit successful).

[rossberg, 2013-07-19 12:54:41]

https://codereview.chromium.org/19054006/diff/13001/src/effects.h
File src/effects.h (right):

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode122
src/effects.h:122: effect = Effect::Seq(locator.value(), effect,
Base::isolate());
On 2013/07/19 12:09:03, Jakob wrote:
> nit: {} please

Done.

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode135
src/effects.h:135: effect = Effect::Alt(locator.value(), effect,
Base::isolate());
On 2013/07/19 12:09:03, Jakob wrote:
> nit: {} please

Done.

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode216
src/effects.h:216: typedef ZoneSplayTree<SplayTreeConfig> Map;
On 2013/07/19 12:09:03, Jakob wrote:
> We already have a v8::internal::Map. Please use another name here. EffectsMap?

Done.

https://codereview.chromium.org/19054006/diff/13001/src/effects.h#newcode248
src/effects.h:248: explicit Effects(Zone* zone) :
On 2013/07/19 12:09:03, Jakob wrote:
> nit: ':' goes on the next line. Line break suggestion:
> 
>   explicit Effects(Zone* zone)
>       : EffectsMixin<Var,
>                      EffectsBase<Var, kNoVar>,
>                      Effects<Var, kNoVar> >(zone) {}

Done (though with fewer breaks)