[turbofan] Cache for reusing value vector nodes in frame states.

[turbofan] Cache for reusing parts of value vector nodes in frame states.

Instead of the current approach of storing flat vectors in frame states (and possibly reusing the last vector in AST graph builder), this change list builds a tree for the values and tries to reuse the nodes for different frame states. At the moment, we only use this for the local variable part of frame state, but nothing prevents us from using this for all parts.

This change provides two new classes: one for creating the tree (StateValuesCache) and one for iterating the trees (StateValuesAccess).

BUG=

Committed: https://crrev.com/cd67e97a7e002811c098b22bfffee44d5db73444
Cr-Commit-Position: refs/heads/master@{#27222}

[Jarin, 2015-03-15 10:07:40]

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

[Jarin, 2015-03-15 10:08:00]

Could you take a look, please?

[Jarin, 2015-03-15 10:09:34]

On 2015/03/15 10:08:00, jarin wrote:
> Could you take a look, please?

(Adding Michi to CC as it is affecting one of his babies.)

[Benedikt Meurer, 2015-03-16 10:18:33]

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
File src/compiler/ast-graph-builder.h (right):

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
src/compiler/ast-graph-builder.h:102: StateValuesCache* state_values_cache_;
Just embed the object at this pointer. There's no need for the pointer
indirection.

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/state-valu...
File src/compiler/state-values-utils.h (right):

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/state-valu...
src/compiler/state-values-utils.h:13: class BitVector;
That seems to be unused in this header.

[Benedikt Meurer, 2015-03-16 10:18:56]

I think this looks good to me. But I need to take another look to be sure.

[Jarin, 2015-03-16 10:26:33]

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
File src/compiler/ast-graph-builder.h (right):

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
src/compiler/ast-graph-builder.h:102: StateValuesCache* state_values_cache_;
On 2015/03/16 10:18:33, Benedikt Meurer wrote:
> Just embed the object at this pointer. There's no need for the pointer
> indirection.

Except that I do not need to include the header if I use the indirection.

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/state-valu...
File src/compiler/state-values-utils.h (right):

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/state-valu...
src/compiler/state-values-utils.h:13: class BitVector;
On 2015/03/16 10:18:33, Benedikt Meurer wrote:
> That seems to be unused in this header.

Removed.

[Benedikt Meurer, 2015-03-16 10:33:35]

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
File src/compiler/ast-graph-builder.h (right):

https://codereview.chromium.org/1008213002/diff/40001/src/compiler/ast-graph-...
src/compiler/ast-graph-builder.h:102: StateValuesCache* state_values_cache_;
"If it would otherwise make sense to use a type as a member by-value, don't
convert it to a pointer just to be able to forward-declare the type."

(http://www.chromium.org/developers/coding-style/cpp-dos-and-donts)

[Benedikt Meurer, 2015-03-16 10:48:46]

LGTM once comment is addressed.

[Jarin, 2015-03-16 13:37:47]

The CQ bit was checked by jarin@chromium.org

[Jarin, 2015-03-16 13:37:48]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/1008213002/#ps80001
(title: "Embed StateValueCache in AstGraphBuilder")

[commit-bot: I haz the power, 2015-03-16 13:37:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1008213002/80001

[commit-bot: I haz the power, 2015-03-16 13:43:07]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-03-16 13:43:24]

Patchset 5 (id:??) landed as
https://crrev.com/cd67e97a7e002811c098b22bfffee44d5db73444
Cr-Commit-Position: refs/heads/master@{#27222}