Vector-ICs - speed towards the monomorphic exit as quickly as possible.

Vector-ICs - speed towards the monomorphic exit as quickly as possible.

Thanks to some careful assumptions, we can examine the object found at
vector[slot] and trust it's a heap object where the second field is
either a map if it's a WeakCell, or definitely not a map if it's a
Symbol, String or FixedArray. Use this to save a memory read.

BUG=

Committed: https://crrev.com/35a67b745d862c5b1f584c2786ebf1369dc4f1ff
Cr-Commit-Position: refs/heads/master@{#27631}

[mvstanton, 2015-04-07 12:55:18]

mvstanton@chromium.org changed reviewers:
+ verwaest@chromium.org

[mvstanton, 2015-04-07 12:55:19]

Hi Toon,
Here is the much-discussed perf. optimization to the vector IC dispatcher.

Note that is not an ia32 port. Ia32 is so register bound that I'd have to offset
any gains with push/pop of some input values. So I don't bother there.

I'll turn off the vector-ic flag before submitting...
--Michael

[Toon Verwaest, 2015-04-07 13:53:28]

lgtm, don't forget to turn if off.

[mvstanton, 2015-04-07 14:28:47]

The CQ bit was checked by mvstanton@chromium.org

[mvstanton, 2015-04-07 14:28:47]

The patchset sent to the CQ was uploaded after l-g-t-m from
verwaest@chromium.org
Link to the patchset: https://codereview.chromium.org/1032163002/#ps80001
(title: "Turn off flag.")

[commit-bot: I haz the power, 2015-04-07 14:28:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1032163002/80001

[commit-bot: I haz the power, 2015-04-07 14:50:04]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-04-07 14:50:23]

Patchset 5 (id:??) landed as
https://crrev.com/35a67b745d862c5b1f584c2786ebf1369dc4f1ff
Cr-Commit-Position: refs/heads/master@{#27631}