When assigning a register to a value that is used as a function
argument, we use a hint to suggest the corresponding register. However,
if the argument is also used after the call, the register will not be
free for the entire live range of the value. Hence we need to split the
live range.
To minimize the number of splits, we aim to choose a register with
maxium availability. This heuristic was implemented based on lifetime
positions with sub-instruction precision. In such a model, argument
registers typically have a shorter available time, as they need to
hold a value before a call, whereas all other registers are free until
right after the call, where they have been overwritten by the called
function. Hence, we typically chose a non-argument register, ignoring
the hint and creating an extra move.
This change moves the heuristic to instruction granularity, which
gives argument and other registers the same free time. We also now
prefer hinted registers if they have the same free time.

Change-Id: Ia8dd73b6c086d28859a836c42ea9ff8afce4c371
Reviewed-on: https://chromium-review.googlesource.com/1124852Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54255}

This is a reland of 52a10e50, after
eliminating an invalid assumption about maps.

TBR=jarin@chromium.org
TBR=mstarzinger@chromium.org

Original change's description:
> [turbofan] Rewrite CompilationDependencies
>
> Instead of installing code dependencies during graph reduction,
> install them after code generation.
>
> Bug: v8:7902, v8:7790
> Change-Id: I8a3798254abb5b9ec7c295a1592aeb6b51f24c7a
> Reviewed-on: https://chromium-review.googlesource.com/1119913
> Commit-Queue: Georg Neis <neis@chromium.org>
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54170}

Bug: v8:7902, v8:7790
Change-Id: I9cbaf98980379b9b17464af5952ec0c47e1cdc6f
Reviewed-on: https://chromium-review.googlesource.com/1126999Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54254}

Previously we were getting the code object from the stack, so printed incorrect
position details for interpreted frames.

BUG=v8:7916

Change-Id: I2f87584117d88b7db3f3b9bdbfe793c4d3e33fe9
Reviewed-on: https://chromium-review.googlesource.com/1126313Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54253}

Bug: v8:7754
Change-Id: Id7701375897f6f3cfac7327404751b43cfdb221c
Reviewed-on: https://chromium-review.googlesource.com/1118888Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54252}

This CL is a manual revert of 3e78711c.

Adding the fast path did not result in any performance improvement,
and actually decreased DataView performance in the performance test.

Change-Id: I149670088b07c31e44d93ed65505254ec0caf8ba
Reviewed-on: https://chromium-review.googlesource.com/1126925Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Théotime Grohens <theotime@google.com>
Cr-Commit-Position: refs/heads/master@{#54251}

Change-Id: I4c86e7ff110b4457a4d52b66462b31b62b42473f
Reviewed-on: https://chromium-review.googlesource.com/1126891Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54250}

R=sigurds@chromium.org

Change-Id: I1af61feff81f21792d66af7d9b12fc59ea94aacd

No-Try: true
No-Tree-Checks: true
Change-Id: I1af61feff81f21792d66af7d9b12fc59ea94aacd
Reviewed-on: https://chromium-review.googlesource.com/1126933
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54249}

This is a first set of test cases for sharing an {WasmEngine} and the
contained {WasmCode} between multiple Isolates. Currently this can only
be done using internal API methods on the Isolate, an external API that
is usable by embedders does not exist yet.

R=clemensh@chromium.org
TEST=cctest/test-wasm-shared-engine
BUG=v8:7424

Change-Id: I35541a76b5aceec4519e3a46e6a9ef4d01cad22b
Reviewed-on: https://chromium-review.googlesource.com/1126382Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54248}

MaybeObjectHandle already has an API for making a weak pointer.

BUG=v8:7308

Change-Id: I9f8390e0dffec850a24391e7f50a455b86b217f5
Reviewed-on: https://chromium-review.googlesource.com/1125922Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54247}

In the WebAssembly fuzzers we detect infinite loops with the
interpreter: if the interpreter does not finish after a finite number
of steps, we do not execute the compiled code. However, we cannot
redirect the start function to the interpreter in the fuzzer, and
therefore we cannot detect infinite loops in the start function. With
this CL we avoid the problem completely by not instantiating a module
in the fuzzer which has a start function. Note that the module still
gets compiled.

R=clemensh@chromium.org

Bug: chromium:858914
Change-Id: Icbbe9a003544918d5267cdd1d9405b21bb681133
Reviewed-on: https://chromium-review.googlesource.com/1126766
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54246}

Replace Is<oddball>(GetIsolate()) calls with a no-parameter version
that goes through ReadOnlyRoots, and add a version that takes a
ReadOnlyRoots if that is available in the parent (but Isolate isn't).

Also opportunistically clean up a few places where ReadOnlyRoots are
available but we still pass in an Isolate parameter.

TBR=yangguo@chromium.org

Bug: v8:7786
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: Icc0b8a7d8f9c6b84c0ec8fe771fcfb75c9dc5468
Reviewed-on: https://chromium-review.googlesource.com/1126302Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54245}

Mips and mips64 generate non-position-independent trampolines once code
exceeds 128K in size. This is a quick fix for failing bots, disabling
the ten largest builtins.

TBR=machenbach@chromium.org

Bug: v8:7882, v8:7920
Change-Id: I027ff8452f927f890773210fb99853adf4934bbc
Reviewed-on: https://chromium-review.googlesource.com/1126923
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54244}

This is a port of e5630ea9:
"[builtins,x64] pc-relative builtin-to-builtin calls".

Bug: v8:6666
Change-Id: Id53bf45c6a4fedb1c972ced72984b6673808ee96
Reviewed-on: https://chromium-review.googlesource.com/1126249Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#54243}

Change-Id: Id6163e68877554d67ae447e6607fb6a5944ac8c9
Reviewed-on: https://chromium-review.googlesource.com/1120166Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#54242}

This is a reland of 2265a852

Original change's description:
> [snapshot] Reduce serialization chunk size to 4K.
>
> This change may slow down deserialization of the snapshot but may result in less fragmentation.
>
> Bug: v8:7887
> Change-Id: Id8bb9f1a561b08b7ae0f10b80aa77bc00eb23172
> Reviewed-on: https://chromium-review.googlesource.com/1125722
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Commit-Queue: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54198}

TBR=hpayer@chromium.org

Bug: v8:7887
Change-Id: If03f241a80341cb053190c5bc0451fe9a032e1a8
Reviewed-on: https://chromium-review.googlesource.com/1126899Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54241}

Now that ReadOnlyRoots is used everywhere to access the read-only roots,
this makes the Heap accessors for such roots private.

It also adds tests that the roots reachable from ReadOnlyRoots are all
in RO_SPACE as well as tests that the roots still publicly accessible
from Heap are not in RO_SPACE. There's a white list in the file for
the few roots where the root pointer itself can change. (For instance
materialized_objects points to empty_fixed_array to start with before
before later pointing to a mutable array).

Also fixes up new use of heap->empty_fixed_array() in elements.cc added
since I cleaned it up.

Bug: v8:7786
Change-Id: I9ac7985c9f85910b5b22d2f9f559dfd04d43ed44
Reviewed-on: https://chromium-review.googlesource.com/1126252Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54240}

We can actually prepare everything in the background, all that remains
to do in the finisher task (on the main thread) is actually adding the
code to the {NativeModule}.
As a next step, even that should happen in the background.

R=mstarzinger@chromium.org

Bug: v8:6600
Change-Id: I570f99a9aa7dc7e324046da36cca9b4297f1bc5e
Reviewed-on: https://chromium-review.googlesource.com/1126391
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54239}

The stack of the wasm interpreter was stored in a zone. However, when
the stack grows, the previous memory of the stack cannot be reused.
With this CL we allocate the stack on the C++ heap to remove this memory
leak.

R=clemensh@chromium.org

Bug: chromium:856594
Change-Id: Idce22c5c1732f7097fc4281c73174892c95f49e2
Reviewed-on: https://chromium-review.googlesource.com/1126301
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54238}

Fixes V8 correctness failure when there's a proxy in the global object
prototype chain and unsuccessful attempt is made to access a property.

Bug: chromium:849024
Change-Id: I829e1a6c038982b7c7a77f8bdefb61facb4614f0
Reviewed-on: https://chromium-review.googlesource.com/1124446
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54237}

The code target vector is used by backends whenever initial code
creation uses immediates that cannot hold a code pointer: An index into
the vector is used instead, and the vector contains the corresponding
code object. This CL makes the code target vector available on all
platforms.

Bug: v8:6666
Change-Id: I2026acd6a77a3465fe2285b84d47866c3b794855
Reviewed-on: https://chromium-review.googlesource.com/1118885
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54236}

If the first object in the space already exceeds the target chunk size,
we would leave the first chunk empty. That violates some assumptions
later when we allocate for deserialization.

R=hpayer@chromium.org, jgruber@chromium.org
TBR=hpayer@chromium.org

Bug: v8:7887
Change-Id: Iee8147fe1205bb6b1c893d48acde1099b5032a14
Reviewed-on: https://chromium-review.googlesource.com/1126763Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54235}

Bug: v8:7790
Change-Id: I053eac9c9b49c65a2f751b1b107e32f7603e63a9
Reviewed-on: https://chromium-review.googlesource.com/1126113Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54234}

This just fixes the text for the '--liftoff' and '--trace-liftoff'
flags to avoid calling Liftoff "experimental".

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: Iff9032070fe0e18ee77debf376f5453d1a61480e
Reviewed-on: https://chromium-review.googlesource.com/1126114Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54233}

After a certain number of iterations in the fixpoint
iteration switch to a linear algorithm. This
algorithm uses a key-to-values map for weak collections
contents to avoid checking all EphemeronHashTables
again.

Bug: chromium:844008
Change-Id: I044fede5911e0a780d088d1ba2bb5343317d9b7a
Reviewed-on: https://chromium-review.googlesource.com/1105835
Commit-Queue: Dominik Inführ <dinfuehr@google.com>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54232}

This reverts commit 5f2f418d.

Reason for revert: Speculative revert for LayoutTest timeouts

https://ci.chromium.org/buildbot/client.v8.fyi/V8-Blink%20Linux%2064/24596
https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8-Blink%20Linux%2064%20-%20future/4707
https://ci.chromium.org/buildbot/client.v8.fyi/V8-Blink%20Linux%2064%20(dbg)/12467

Original change's description:
> [scanner] Rewrite character streams by separating underlying bytestreams from buffering.
> 
> Additionally now we only scan over flat heap strings.
> 
> Change-Id: Ic449b19aecd7fc3f283a04a3df6a39772d471565
> Reviewed-on: https://chromium-review.googlesource.com/1125854
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Commit-Queue: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54224}

TBR=marja@chromium.org,verwaest@chromium.org

Change-Id: Ica3026f318a85ec6bb24a38a8cd998f12c146d7e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1126819Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54231}

This is just derived from is_wasm_memory.

Change-Id: I2f77fb5e32e325c51de9af4228ca33313c21abc6
Reviewed-on: https://chromium-review.googlesource.com/1126107Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54230}

Only pass around the unadulterated value identifier in the VisitResult class
until the very last moment before code generation, at which point the
declaration that was used to originally define the value is used to generate the
correct final source code string in the context of a l-value or r-value.

Bug: v8:7793
Change-Id: Ifd0c0d245b2eb65c7f3ddb1ad4c87ee235c54a82
Reviewed-on: https://chromium-review.googlesource.com/1125063
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54229}

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/de0662d..0cc2895

TBR=machenbach@chromium.org,hablich@chromium.org,sergiyb@chromium.org

Change-Id: Ib114c478943e00e4bfb6b688e5471569217e070e
Reviewed-on: https://chromium-review.googlesource.com/1126569
Commit-Queue: V8 Autoroller <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Reviewed-by: V8 Autoroller <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#54228}

Port 34225a6a

Original Commit Message:

    For spread calls with arrays with double elements but zero length,
    we skip the box-as-heapnumber step; so in this corner case the
    Call builtin sees a FixedDoubleArray, which is fine because it
    doesn't read any of the raw double values from it.
    This patch doesn't change the implementation, it only updates the
    assert to match reality.

R=jkummerow@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: Iafa52f21fb0bbee5656fdfd6c5f3a50894ff683f
Reviewed-on: https://chromium-review.googlesource.com/1126212Reviewed-by: Michael Dawson <michael_dawson@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#54227}

This DCHECK does not hold for compaction spaces that may go over the limit
with large semi-spaces and small old generation size maxima.

Bug: chromium:855960
Change-Id: I39eea4c974b94c170e7314471fb1c50f9a1a2b45
Reviewed-on: https://chromium-review.googlesource.com/1126392Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54226}

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/7ac2934..de0662d

Rolling v8/third_party/catapult: https://chromium.googlesource.com/catapult/+log/153acbd..8221306

Rolling v8/third_party/depot_tools: https://chromium.googlesource.com/chromium/tools/depot_tools/+log/605dd31..5484b86

Rolling v8/third_party/fuchsia-sdk: https://chromium.googlesource.com/chromium/src/third_party/fuchsia-sdk/+log/b334665..272de12

Rolling v8/tools/clang: https://chromium.googlesource.com/chromium/src/tools/clang/+log/39163b8..d8cde7f

Rolling v8/tools/luci-go: https://chromium.googlesource.com/chromium/src/tools/luci-go/+log/0e27f88..e3d4003

TBR=machenbach@chromium.org,hablich@chromium.org,sergiyb@chromium.org

Change-Id: Ie71d071d1a3a818a61c4db617b0d09ee41304552
Reviewed-on: https://chromium-review.googlesource.com/1126446
Commit-Queue: V8 Autoroller <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Reviewed-by: V8 Autoroller <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#54225}

Additionally now we only scan over flat heap strings.

Change-Id: Ic449b19aecd7fc3f283a04a3df6a39772d471565
Reviewed-on: https://chromium-review.googlesource.com/1125854Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54224}

In future the RO_SPACE root accessors in Heap will become private, so
instead convert them all to use ReadOnlyRoots.

Bug: v8:7786
Change-Id: I315e63a30ca6f3077f18eb1a5004daefba9bc673
Reviewed-on: https://chromium-review.googlesource.com/1125929
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54223}

R=jarin@chromium.org

Change-Id: I3a6759468f1a21b84ab9a294a2ca41d70b9cec99
Reviewed-on: https://chromium-review.googlesource.com/1123829Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54222}

In future the RO_SPACE root accessors in Heap will become private, so
instead convert them all to use ReadOnlyRoots.

Bug: v8:7786
Change-Id: Ib3c45c1023d76bec5e1f4bc8f971062880b6c53f
Reviewed-on: https://chromium-review.googlesource.com/1126240Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54221}

Changes SharedFunctionInfo to store a function_token_offset, relative
to the start_position, instead of the full function_token_position.
This enables us to reduce both FunctionTokenPosition and
ExpectedNofProperties to 16 bits each, saving 32 bits per SFI.

BUG=chromium:818642,chromium:783853
TBR=yangguo@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I45aefcec605c1da502053c23c73564ceaed6c9b5
Reviewed-on: https://chromium-review.googlesource.com/1122982
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54220}

BUG=chromium:859809

Change-Id: I9ac81585c7f141cb1839ff7de237e0930f44e634
Reviewed-on: https://chromium-review.googlesource.com/1124450Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54219}

This is a reland of ade7f55b

Previously landed as: ade7f55b / 1125679
Previously landed as: 3c4d0316 / 1065818
Previously landed as: 8e0f67be / 1088890

Original change's description:
> Reland ^2 "[async] Expose async hooks to d8"
>
> This is a reland of 8e0f67be
>

Bug: chromium:850530
Change-Id: I536cfb9443d80d62937d9c3dc6a53b52b209d5c7
Reviewed-on: https://chromium-review.googlesource.com/1125683
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54218}

This CL creates a new Operator called LoadDataViewElement, similar to
LoadTypedArray, for DataView getters.

This operator will be used as a wrapper around all the computations
that DataViews need to do when loading values, due to the endianness
parameter of DataView loads.

Change-Id: Ie67d63c9669142e539a5c8d7ae82dc1018ce5858
Reviewed-on: https://chromium-review.googlesource.com/1125928
Commit-Queue: Théotime Grohens <theotime@google.com>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54217}

In future the RO_SPACE root accessors in Heap will become private, so
instead convert them all to use ReadOnlyRoots.

Bug: v8:7786
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I4a5fb4bc70169874d003d9c31f1713f52e2bba93
Reviewed-on: https://chromium-review.googlesource.com/1126118Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54216}