Make sure backing store pointer in handles get cleared after use in factory.

BUG=442710
LOG=n

Review URL: https://codereview.chromium.org/813023002

Cr-Commit-Position: refs/heads/master@{#25881}
Monomorphic and polymorphic ICs with cleared maps should not go megamorphic.

BUG=v8:3663
TEST=cctest/test-heap/MonomorphicStaysMonomorphicAfterGC
LOG=N

Review URL: https://codereview.chromium.org/816653002

Cr-Commit-Position: refs/heads/master@{#25882}
Temporarily disable mjsunit/debug-stepframe for GC stress until
crash is fixed.

BUG=v8:3776
LOG=N
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/812283004

Cr-Commit-Position: refs/heads/master@{#25883}
Revert of [turbofan] remove control field from instruction (patchset #1 id:1 of https://codereview.chromium.org/810023002/)

Reason for revert:
Needed to revert https://chromium.googlesource.com/v8/v8/+/70b5eb47b39acbf31746f4a116a9b3ce2730218a

Original issue's description:
> [turbofan] remove control field from instruction
>
> R=titzer@chromium.org
> BUG=
>
> Committed: https://crrev.com/7b9cb2eb3764d0c807c669e397fc3b84fbefb175
> Cr-Commit-Position: refs/heads/master@{#25866}

TBR=titzer@chromium.org,dcarney@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/814043002

Cr-Commit-Position: refs/heads/master@{#25884}
Reduce impact of HParameter inputs on HPhi representation selection

This is a follow-up to r25153.

BUG=v8:3766
LOG=n

Review URL: https://codereview.chromium.org/807273003

Cr-Commit-Position: refs/heads/master@{#25885}
Revert of [turbofan] Skip printing of empty gap moves. (patchset #1 id:1 of https://codereview.chromium.org/812983002/)

Reason for revert:
Needed to revert https://chromium.googlesource.com/v8/v8/+/70b5eb47b39acbf31746f4a116a9b3ce2730218a

Original issue's description:
> [turbofan] Skip printing of empty gap moves.
>
> R=bmeurer@chromium.org
> BUG=

TBR=bmeurer@chromium.org,titzer@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/816703002

Cr-Commit-Position: refs/heads/master@{#25886}
Retain maps for several garbage collections

This keeps dying maps alive for FLAG_retain_maps_for_n_gc garbage collections to increase chances of them being reused for new objects in future.

BUG=v8:3664
LOG=N
TEST=cctest/test-heap/MapRetaining

Review URL: https://codereview.chromium.org/794583003

Cr-Commit-Position: refs/heads/master@{#25887}
Revert of [turbofan] simplify gap ordering (patchset #2 id:20001 of https://codereview.chromium.org/810013002/)

Reason for revert:
Revert for breaking emscripten bullet with turbofan on android arm64.

Original issue's description:
> [turbofan] simplify gap ordering
>
> BUG=
>
> Committed: https://crrev.com/70b5eb47b39acbf31746f4a116a9b3ce2730218a
> Cr-Commit-Position: refs/heads/master@{#25865}

TBR=bmeurer@chromium.org,dcarney@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/815743002

Cr-Commit-Position: refs/heads/master@{#25888}
Phantom references support internal fields

BUG=

Review URL: https://codereview.chromium.org/753553002

Cr-Commit-Position: refs/heads/master@{#25889}
Reland Shrink initial old generation size based on new space survival rate.

I picked a more conservative start value this time of half max old generation size.

BUG=

Review URL: https://codereview.chromium.org/804323004

Cr-Commit-Position: refs/heads/master@{#25890}
ES6 template literals should not use legacy octal strings

Correctly handle SyntaxErrors in escape sequences.

BUG=v8:3736
LOG=Y
R=dslomov@chromium.org, caitpotter88@gmail.com

Review URL: https://codereview.chromium.org/811113002

Cr-Commit-Position: refs/heads/master@{#25891}