[turbofan] Add support for advanced reducers.

[turbofan] Add support for advanced reducers.

An AdvancedReducer is basically a regular Reducer with an editor
that can perform graph editing operations beyond changing or
replacing the node that is currently being reduced. The GraphReducer
is the default implementation of the AdvancedReducer::Editor interface.

The ControlReducerImpl is now just an AdvancedReducer, which
temporarily requires a Finish method in the reducer to implement
the dead node trimming until we move that to the GraphReducer
(which in turn requires that all loops are connected to End).

Committed: https://crrev.com/7b33409ba3fbb7853b854fea68d6a3dcbd387787
Cr-Commit-Position: refs/heads/master@{#28251}

[Benedikt Meurer, 2015-05-06 07:19:13]

bmeurer@chromium.org changed reviewers:
+ titzer@chromium.org

[titzer, 2015-05-06 08:57:40]

https://codereview.chromium.org/1122423003/diff/20001/src/compiler/graph-redu...
File src/compiler/graph-reducer.h (right):

https://codereview.chromium.org/1122423003/diff/20001/src/compiler/graph-redu...
src/compiler/graph-reducer.h:45: class Observer {
As discussed, if we could move this out of the base reducer and only have it in
the AdvancedReducer, then I'm (grumble) OK with this change.

[Benedikt Meurer, 2015-05-06 09:10:32]

PTAL

https://codereview.chromium.org/1122423003/diff/20001/src/compiler/graph-redu...
File src/compiler/graph-reducer.h (right):

https://codereview.chromium.org/1122423003/diff/20001/src/compiler/graph-redu...
src/compiler/graph-reducer.h:45: class Observer {
Done as discussed. However I kept the Finish method in the Reducer to avoid
having the GraphReducer to distinguish Reducer and AdvancedReducer instances.
I'll work on readding Terminate and moving the trimming to GraphReducer, so we
can remove that Finish hack really soonish.

[titzer, 2015-05-06 09:22:08]

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
File src/compiler/graph-reducer.cc (right):

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
src/compiler/graph-reducer.cc:187: void GraphReducer::Replace(Node* node, Node*
replacement) {
I prefer the simplification in my other CL which made this into one method.

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
File src/compiler/graph-reducer.h (right):

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
src/compiler/graph-reducer.h:134: bool Finish() {
Why do we need this in the header?

[Benedikt Meurer, 2015-05-06 09:33:30]

Done.

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
File src/compiler/graph-reducer.cc (right):

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
src/compiler/graph-reducer.cc:187: void GraphReducer::Replace(Node* node, Node*
replacement) {
On 2015/05/06 09:22:08, titzer wrote:
> I prefer the simplification in my other CL which made this into one method.

Done.

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
File src/compiler/graph-reducer.h (right):

https://codereview.chromium.org/1122423003/diff/40001/src/compiler/graph-redu...
src/compiler/graph-reducer.h:134: bool Finish() {
On 2015/05/06 09:22:08, titzer wrote:
> Why do we need this in the header?

Done.

[titzer, 2015-05-06 09:38:44]

lgtm

https://codereview.chromium.org/1122423003/diff/60001/src/compiler/graph-redu...
File src/compiler/graph-reducer.cc (right):

https://codereview.chromium.org/1122423003/diff/60001/src/compiler/graph-redu...
src/compiler/graph-reducer.cc:163: // If {replacement}  is an old node, unlink
{node} and assume that
Move this comment into the branch within the Replace() method below.

[Benedikt Meurer, 2015-05-06 09:42:56]

https://codereview.chromium.org/1122423003/diff/60001/src/compiler/graph-redu...
File src/compiler/graph-reducer.cc (right):

https://codereview.chromium.org/1122423003/diff/60001/src/compiler/graph-redu...
src/compiler/graph-reducer.cc:163: // If {replacement}  is an old node, unlink
{node} and assume that
On 2015/05/06 09:38:44, titzer wrote:
> Move this comment into the branch within the Replace() method below.

Done.

[Benedikt Meurer, 2015-05-06 09:43:00]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-05-06 09:43:01]

The patchset sent to the CQ was uploaded after l-g-t-m from titzer@chromium.org
Link to the patchset: https://codereview.chromium.org/1122423003/#ps80001
(title: "Move comment")

[commit-bot: I haz the power, 2015-05-06 09:43:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1122423003/80001

[commit-bot: I haz the power, 2015-05-06 10:12:52]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-05-06 10:13:03]

Patchset 5 (id:??) landed as
https://crrev.com/7b33409ba3fbb7853b854fea68d6a3dcbd387787
Cr-Commit-Position: refs/heads/master@{#28251}