[heap] Simplify clearing of normalized map caches.

[heap] Simplify clearing of normalized map caches.

Currently the incremental marking visitor treats elements of normalized
map caches weakly by coloring the caches grey without pusing to marking
deque.

The mark-compact prologue then clears all normalized map caches.

We can achieve similar effect by just clearing the caches in the marking
visitor.

BUG=chromium:694255
Review-Url: https://codereview.chromium.org/2745183002
Cr-Commit-Position: refs/heads/master@{#43941}
Committed: https://chromium.googlesource.com/v8/v8/+/3d68306c71b17ebcb306b4e2ed8cae110c52229c

[ulan, 2017-03-13 14:36:00]

ulan@chromium.org changed reviewers:
+ hpayer@chromium.org, verwaest@chromium.org

[ulan, 2017-03-13 14:36:01]

Hannes, ptal.

Toon, fyi.

https://codereview.chromium.org/2745183002/diff/1/src/heap/heap.cc
File src/heap/heap.cc (left):

https://codereview.chromium.org/2745183002/diff/1/src/heap/heap.cc#oldcode1253
src/heap/heap.cc:1253: if (isolate_->bootstrapper()->IsActive() &&
I don't understand the intent of this condition. We don't clear the caches if
the bootstrapper is active and we're doing full GC.

This is going to change to clearing unconditionally.

[Hannes Payer (out of office), 2017-03-20 14:18:31]

lgtm

[ulan, 2017-03-20 14:28:59]

The CQ bit was checked by ulan@chromium.org

[commit-bot: I haz the power, 2017-03-20 14:29:11]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-20 14:55:50]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1490020139386990, "parent_rev":
"dc789377a1a6ef4a50e100830ff83cbc3b98dba4", "commit_rev":
"3d68306c71b17ebcb306b4e2ed8cae110c52229c"}

[commit-bot: I haz the power, 2017-03-20 14:55:55]

Description was changed from

==========
[heap] Simplify clearing of normalized map caches.

Currently the incremental marking visitor treats elements of normalized
map caches weakly by coloring the caches grey without pusing to marking
deque.

The mark-compact prologue then clears all normalized map caches.

We can achieve similar effect by just clearing the caches in the marking
visitor.

BUG=chromium:694255
==========

to

==========
[heap] Simplify clearing of normalized map caches.

Currently the incremental marking visitor treats elements of normalized
map caches weakly by coloring the caches grey without pusing to marking
deque.

The mark-compact prologue then clears all normalized map caches.

We can achieve similar effect by just clearing the caches in the marking
visitor.

BUG=chromium:694255

Review-Url: https://codereview.chromium.org/2745183002
Cr-Commit-Position: refs/heads/master@{#43941}
Committed:
https://chromium.googlesource.com/v8/v8/+/3d68306c71b17ebcb306b4e2ed8cae110c5...
==========

[commit-bot: I haz the power, 2017-03-20 14:55:56]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/v8/v8/+/3d68306c71b17ebcb306b4e2ed8cae110c5...

[ulan, 2017-03-23 08:59:30]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/2771703003/ by ulan@chromium.org.

The reason for reverting is:
https://bugs.chromium.org/p/v8/issues/detail?id=6135.