This removes:
- CodeBreakIterator for FCG code.
- RelocModes for debug breaks.
- Code generator for debug break slots.
- GC support for debug break slots.
- Code flag to indicate code with debug break slots.
- Builtin type DBG.
- Mechanisms to replace FCG code in the debugger and LiveEdit.
- Runtime entry to the debugger from debug break slots.

R=bmeurer@chromium.org, rmcilroy@chromium.org, ulan@chromium.org

Bug: v8:6409
Change-Id: I5662c8800e3ef1b1584ad107bfe0aae26c9d8abb
Reviewed-on: https://chromium-review.googlesource.com/613263Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47364}

This is a reland of 35c923cc
Original change's description:
> [heap] Add support for atomic access to page flags.
> 
> This patch renames AsAtomicWord to AsAtomicPointer and
> adds new AsAtomicWord that works with intptr_t.
> 
> Slot recording uses atomic page flag accessors.
> 
> BUG=chromium:694255
> 
> Change-Id: I1c692813244b41320182e9eea50462d1802fcd98
> Reviewed-on: https://chromium-review.googlesource.com/597688
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47086}

Bug: chromium:694255
Change-Id: I36780ff4001e068815d4be1e16cd06f1a4f98d13
Reviewed-on: https://chromium-review.googlesource.com/599909Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47131}

This reverts commit 35c923cc.

Reason for revert: speculative revert for GC stress failure

Original change's description:
> [heap] Add support for atomic access to page flags.
> 
> This patch renames AsAtomicWord to AsAtomicPointer and
> adds new AsAtomicWord that works with intptr_t.
> 
> Slot recording uses atomic page flag accessors.
> 
> BUG=chromium:694255
> 
> Change-Id: I1c692813244b41320182e9eea50462d1802fcd98
> Reviewed-on: https://chromium-review.googlesource.com/597688
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47086}

TBR=ulan@chromium.org,mlippautz@chromium.org

Change-Id: Id77ce7970c54a55646c072787e88311f6f3e6e91
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:694255
Reviewed-on: https://chromium-review.googlesource.com/598967Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47094}

This patch renames AsAtomicWord to AsAtomicPointer and
adds new AsAtomicWord that works with intptr_t.

Slot recording uses atomic page flag accessors.

BUG=chromium:694255

Change-Id: I1c692813244b41320182e9eea50462d1802fcd98
Reviewed-on: https://chromium-review.googlesource.com/597688
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47086}

Change-Id: Ida5c537fa94a376a134e60edce889b96b676a8f9
Reviewed-on: https://chromium-review.googlesource.com/584874Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47039}

This will allow us to concurrently allocate buckets during iteration.

Bug: chromium:738865
Change-Id: I88bd1ac152d1ef8b40395f0ba3e55a7c3e82f75d
Reviewed-on: https://chromium-review.googlesource.com/575990
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46737}

Bug: chromium:738865
Change-Id: I4c8aa8c90ba401200222d95d6395c022fc023a71
Reviewed-on: https://chromium-review.googlesource.com/574535
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46715}

A follow up will allow inserting slots during GC without emiting fences

Bug: chromium:651354
Change-Id: Ia1d0f88e3658bca31933bdb013db15a5c2ecd849
Reviewed-on: https://chromium-review.googlesource.com/541400
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46042}

This avoids emitting the costly barriers on arm.

Bug: chromium:651354
Change-Id: Ibb29e58f7c41aab37ed5c4971b2a754b4ecd7155
Reviewed-on: https://chromium-review.googlesource.com/533337
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46011}

This patch makes the SlotSet bucket type non-atomic by default
and explicitly converts buckets to Atomic32/AtomicWord for each
operation.

Change-Id: Ifaa60a53eb68ca579185be23e379995aeeabe343
Reviewed-on: https://chromium-review.googlesource.com/535481
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45971}

BUG=chromium:666046

Review-Url: https://codereview.chromium.org/2539503002
Cr-Commit-Position: refs/heads/master@{#41330}

Additionally, remove all code related to the old-style slots filtering and black area end markers.

BUG=chromium:648568

Review-Url: https://chromiumcodereview.appspot.com/2440683002
Cr-Commit-Position: refs/heads/master@{#40494}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2428493003
Cr-Commit-Position: refs/heads/master@{#40393}

Revert of [heap] Move slot filtering logic into sweeper. (patchset #4 id:60001 of https://codereview.chromium.org/2418773002/ )

Reason for revert:
[Sheriff] Speculative revert for heap corruption on all platforms, e.g.:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20-%20debug/builds/12377
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20-%20debug/builds/12379
https://build.chromium.org/p/client.v8/builders/V8%20Win32/builds/4819
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20nosnap%20-%20shared/builds/16783
https://build.chromium.org/p/client.v8/builders/V8%20Mac64%20-%20debug/builds/10007

Original issue's description:
> [heap] Move slot filtering logic into sweeper.
>
> BUG=chromium:648568
>
> Committed: https://crrev.com/18db69c38c93450c1ae957999fc48c465f111f00
> Cr-Commit-Position: refs/heads/master@{#40267}

TBR=ulan@chromium.org,mlippautz@chromium.org,hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2418053002
Cr-Commit-Position: refs/heads/master@{#40292}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2418773002
Cr-Commit-Position: refs/heads/master@{#40267}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2403423007
Cr-Commit-Position: refs/heads/master@{#40221}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2412453003
Cr-Commit-Position: refs/heads/master@{#40176}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2409163002
Cr-Commit-Position: refs/heads/master@{#40174}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2397373002
Cr-Commit-Position: refs/heads/master@{#40075}

Revert of [heap] Concurrent slot filtering in sweeper threads. (patchset #4 id:60001 of https://codereview.chromium.org/2401563002/ )

Reason for revert:
Crashing.

Original issue's description:
> [heap] Concurrent slot filtering in sweeper threads.
>
> This is an intermediate step for concurrent slot filtering. This CL already makes filtering concurrent, but does not integrate it in the actual sweeping. This will be done in two follow up CLs. One for the regular slot set and one for the typed slot set.
>
> BUG=chromium:648568
>
> Committed: https://crrev.com/1f89d369fc952a2826f9f62901fb84fcf30920d7
> Cr-Commit-Position: refs/heads/master@{#40040}

TBR=ulan@chromium.org,mlippautz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2399003002
Cr-Commit-Position: refs/heads/master@{#40043}

This is an intermediate step for concurrent slot filtering. This CL already makes filtering concurrent, but does not integrate it in the actual sweeping. This will be done in two follow up CLs. One for the regular slot set and one for the typed slot set.

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2401563002
Cr-Commit-Position: refs/heads/master@{#40040}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2397473004
Cr-Commit-Position: refs/heads/master@{#40034}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2390743005
Cr-Commit-Position: refs/heads/master@{#39982}

BUG=chromium:650577,chromium:648568

Review-Url: https://codereview.chromium.org/2372933003
Cr-Commit-Position: refs/heads/master@{#39767}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2366393002
Cr-Commit-Position: refs/heads/master@{#39735}

Revert of [heap] Reland Concurrently free empty typed slot set chunks. (patchset #2 id:20001 of https://codereview.chromium.org/2365603002/ )

Reason for revert:
Leaks and TSAN:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20ASAN/builds/15441
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/11867

Original issue's description:
> [heap] Reland Concurrently free empty typed slot set chunks.
>
> BUG=chromium:648568
>
> Committed: https://crrev.com/ec3835751d678c0b4a3fda47d11ffa107cd27e23
> Cr-Commit-Position: refs/heads/master@{#39630}

TBR=ulan@chromium.org,hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2364603002
Cr-Commit-Position: refs/heads/master@{#39632}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2365603002
Cr-Commit-Position: refs/heads/master@{#39630}

BUG=chromium:648973,chromium:648568

Review-Url: https://codereview.chromium.org/2360233002
Cr-Commit-Position: refs/heads/master@{#39624}

Revert of [heap] Concurrently free empty typed slot set chunks. (patchset #3 id:40001 of https://codereview.chromium.org/2352423002/ )

Reason for revert:
TSAN failures on Linux64:

https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/11850

Also saw various threading-related flakiness on multiple bots.

Original issue's description:
> [heap] Concurrently free empty typed slot set chunks.
>
> BUG=chromium:648568
>
> Committed: https://crrev.com/ff8101d8e8d5e14dfa89de1252c510e6a0775539
> Cr-Commit-Position: refs/heads/master@{#39605}

TBR=ulan@chromium.org,hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2358333002
Cr-Commit-Position: refs/heads/master@{#39607}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2352423002
Cr-Commit-Position: refs/heads/master@{#39605}

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2360513002
Cr-Commit-Position: refs/heads/master@{#39596}

Here we only change the type of the slot set fields to atomic values and use CAS to change the state. There is no change in behavior or semantics of the slot set.

BUG=chromium:648568

Review-Url: https://codereview.chromium.org/2353553003
Cr-Commit-Position: refs/heads/master@{#39557}

V8 doesn't build on Ubuntu 16.04 (with GCC 5.3). Seems to be
a known regression on newer GCC version. It emits incorrect
"error: array subscript is above array bounds" message. Adding
explicit array bound check fixes the issue.

R=hablich@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2256113002
Cr-Commit-Position: refs/heads/master@{#38721}

BUG=chromium:624544
LOG=NO

Review-Url: https://codereview.chromium.org/2110213003
Cr-Commit-Position: refs/heads/master@{#37451}

We need the host address in another CL to clear invalid slots.

R=ulan@chromium.org

Review-Url: https://codereview.chromium.org/2025833002
Cr-Commit-Position: refs/heads/master@{#36696}

Properly records entries individually instead of using the hammer that requires
visiting the whole code object during pointer updating.

BUG=chromium:612847
LOG=N

Review-Url: https://codereview.chromium.org/1994653002
Cr-Commit-Position: refs/heads/master@{#36334}

Reland "Replace slots buffer with remembered set. (patchset #14 id:250001 of https://codereview.chromium.org/1703823002/ )"

This reverts commit 9146bc5e.

This contains a fix for the following crash:
1. We record slots for a fixed array.
2. We trim the fixed array, so that some recorded slots are now in free space.
3. During mark-compact we sweep the page with the fixed array. Now free list items contain memory with recorded slots.
4. We evacuate a byte array using the new free list items.
5. We iterate slots that are now inside the byte array and crash.

BUG=chromium:589413,chromium:578883
LOG=NO

Review URL: https://codereview.chromium.org/1735523002

Cr-Commit-Position: refs/heads/master@{#34302}

Revert of Replace slots buffer with remembered set. (patchset #14 id:250001 of https://codereview.chromium.org/1703823002/ )

Reason for revert:
Revert because of canary crashes: crbug.com/589413

Original issue's description:
> Replace slots buffer with remembered set.
>
> Slots pointing to evacuation candidates are now recorded in the new RememberedSet<OLD_TO_OLD>.
>
> The remembered set is extended to support typed slots.
>
> During parallel evacuation all migration slots are recorded in local slots buffers.
> After evacuation all local slots are added to the remembered set.
>
> BUG=chromium:578883
> LOG=NO
>
> Committed: https://crrev.com/2285a99ef6f7d52f4f0c4d88a7db4224443ee152
> Cr-Commit-Position: refs/heads/master@{#34212}

TBR=jochen@chromium.org,hpayer@chromium.org,mlippautz@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:578883

Review URL: https://codereview.chromium.org/1725073003

Cr-Commit-Position: refs/heads/master@{#34238}

Slots pointing to evacuation candidates are now recorded in the new RememberedSet<OLD_TO_OLD>.

The remembered set is extended to support typed slots.

During parallel evacuation all migration slots are recorded in local slots buffers.
After evacuation all local slots are added to the remembered set.

BUG=chromium:578883
LOG=NO

Review URL: https://codereview.chromium.org/1703823002

Cr-Commit-Position: refs/heads/master@{#34212}

If sweeping is in progress then we need to filter out slots in free space after
array trimming, because the sweeper will add the free space into free list.

This CL also fixes a bug in SlotSet::RemoveRange.

BUG=chromium:587004
LOG=NO
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1701963003

Cr-Commit-Position: refs/heads/master@{#34071}