Commit Graph

5868 Commits

Author SHA1 Message Date
neis
457c02573c Make toLocaleString on arrays always call toLocaleString on its elements.
As required by the spec.

BUG=v8:5113

Review-Url: https://codereview.chromium.org/2141603002
Cr-Commit-Position: refs/heads/master@{#37689}
2016-07-12 17:33:36 +00:00
neis
8f1f1cb1c7 Move catch prediction into frontend and make it aware of rethrows.
This solves an issue with throws inside for-of always being marked as caught.

BUG=v8:5183

Review-Url: https://codereview.chromium.org/2146493002
Cr-Commit-Position: refs/heads/master@{#37686}
2016-07-12 15:23:35 +00:00
cbruni
d234118e29 Revert of making heap verification more aggressive (patchset #7 id:120001 of https://codereview.chromium.org/2126613002/ )
Reason for revert:
failing gc stress tests: https://build.chromium.org/p/client.v8/builders/V8%20Mac%20GC%20Stress/builds/7223/steps/Mjsunit/logs/stdio

Original issue's description:
> [runtime] making heap verification more aggressive
>
> - check that packed elements do not contain the_hole (with fix)
> - verify argument objects with elements kind
> - use JSObjectVerifiy in all JSObject "subclasses"
> - change initialization order for ArrayLiteralBoilerplate to simplify verification
>
> BUG=v8:5188
>
> Committed: https://crrev.com/599aa2e106ca8ab79f5cc489d1b93b6a26b19714
> Cr-Commit-Position: refs/heads/master@{#37680}

TBR=ishell@chromium.org,ulan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5188

Review-Url: https://codereview.chromium.org/2140163002
Cr-Commit-Position: refs/heads/master@{#37682}
2016-07-12 14:07:17 +00:00
cbruni
599aa2e106 [runtime] making heap verification more aggressive
- check that packed elements do not contain the_hole (with fix)
- verify argument objects with elements kind
- use JSObjectVerifiy in all JSObject "subclasses"
- change initialization order for ArrayLiteralBoilerplate to simplify verification

BUG=v8:5188

Review-Url: https://codereview.chromium.org/2126613002
Cr-Commit-Position: refs/heads/master@{#37680}
2016-07-12 13:32:03 +00:00
mstarzinger
6e38f4270a [test] Remove NaCl support from test runner harness.
R=machenbach@chromium.org

Review-Url: https://codereview.chromium.org/2141013002
Cr-Commit-Position: refs/heads/master@{#37678}
2016-07-12 13:18:49 +00:00
mstarzinger
88402eccc7 [turbofan] Re-enable tests no longer failing on ARM hardware.
R=machenbach@chromium.org

Review-Url: https://codereview.chromium.org/2141563002
Cr-Commit-Position: refs/heads/master@{#37677}
2016-07-12 12:44:11 +00:00
mstarzinger
f3ca214222 [turbofan] Speed up structural graph verification.
This removes the checking for use-def and def-use chain links from the
graph verification. Presence of such links can only be violated by a bug
in the actual {Node} implementation itself. That container class is also
covered by unit tests.

The verification in question was useful in the early days when the graph
implementation itself was prone to bugs. By now it has stabilized and
spending O(n^2) time during graph verification is too wasteful to still
be considered a reasonable trade-off.

R=jarin@chromium.org
TEST=unittests/NodeTest.*

Review-Url: https://codereview.chromium.org/2140973003
Cr-Commit-Position: refs/heads/master@{#37670}
2016-07-12 09:31:12 +00:00
bmeurer
4e862dd964 [intrinsics] Remove obsolete intrinsics.
Remove obsolete definitions from macros.py, and drop the now obsolete
%_ToPrimitive, %_ToPrimitive_Number, %_ToPrimitive_String, %_ToName
and the %ToPrimitive_String intrinsics/runtime entries.

R=yangguo@chromium.org
BUG=v8:5049

Review-Url: https://codereview.chromium.org/2137203002
Cr-Commit-Position: refs/heads/master@{#37665}
2016-07-12 06:41:23 +00:00
yangguo
bbb2159d4c [regexp] Fix regexp source escaping with preceding backslashes.
R=franzih@chromium.org
BUG=chromium:515897

Review-Url: https://codereview.chromium.org/2137033002
Cr-Commit-Position: refs/heads/master@{#37664}
2016-07-12 05:36:17 +00:00
jochen
992e34c216 Don't compile functions in a context the caller doesn't have access to
Instead just return undefined

A side effect of this is that it's no longer possible to compile
functions in a detached context.

BUG=chromium:541703
R=verwaest@chromium.org,bmeurer@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng

Review-Url: https://codereview.chromium.org/2034083002
Cr-Commit-Position: refs/heads/master@{#37657}
2016-07-11 20:11:51 +00:00
littledan
77cbe27689 Narrowly address async function stack overflow parsing case
This patch just checks for a stack overflow and returns failure
from the cases which Clusterfuzz found. However, there may be
more locations in the parser which need similar treatment.

R=caitpotter88@gmail.com,neis
BUG=v8:4483,chromium:624300

Review-Url: https://codereview.chromium.org/2135503002
Cr-Commit-Position: refs/heads/master@{#37655}
2016-07-11 19:33:43 +00:00
aseemgarg
8474f24450 [wasm] throw in case of assignment to module parameters
BUG=613928
R=bradnelson@chromium.org
TEST=regress-613928.js

Review-Url: https://codereview.chromium.org/2123283007
Cr-Commit-Position: refs/heads/master@{#37653}
2016-07-11 17:41:30 +00:00
ishell
b030a6f59d [runtime] Follow-up fix for "Better encapsulation of dictionary objects handling in lookup iterator."
BUG=chromium:626715

Review-Url: https://codereview.chromium.org/2135253002
Cr-Commit-Position: refs/heads/master@{#37651}
2016-07-11 15:51:58 +00:00
mstarzinger
f57b0604ed [crankshaft] Re-enable Math.min/max tests that no longer fail.
R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2132373002
Cr-Commit-Position: refs/heads/master@{#37635}
2016-07-11 11:14:00 +00:00
caitp
08d0012dda [keys] propagate PropertyFilter to proxy targets in KeyAccumulator
BUG=v8:5174, v8:1543
R=cbruni@chromium.org, littledan@chromium.org

Review-Url: https://codereview.chromium.org/2129193003
Cr-Commit-Position: refs/heads/master@{#37634}
2016-07-11 10:39:35 +00:00
jgruber
be5808bff8 Correctly format builtin constructors in stack traces
CallSite::IsConstructor() was unable to recognize builtin construct stubs
(NumberConstructor_ConstructStub and StringConstructor_ConstructStub) as
constructors, and thus these frames were not formatted correctly in stack
traces.

Fix this by explicitly marking their Code objects as construct stubs and
passing along a special receiver value when we encounter such cases in
CaptureSimpleStackTrace.

R=mstarzinger@chromium.org, yangguo@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2125163004
Cr-Commit-Position: refs/heads/master@{#37631}
2016-07-11 10:05:03 +00:00
yangguo
dfcc5d4ee8 [debugger] omit exception events for rethrown exceptions in async.
R=bmeurer@chromium.org, littledan@chromium.org
BUG=v8:5167

Review-Url: https://codereview.chromium.org/2124813002
Cr-Commit-Position: refs/heads/master@{#37623}
2016-07-11 05:50:03 +00:00
mstarzinger
3660505e5f [turbofan] Re-enable debugger tests that no longer fail.
R=yangguo@chromium.org

Review-Url: https://codereview.chromium.org/2127423002
Cr-Commit-Position: refs/heads/master@{#37609}
2016-07-08 12:49:53 +00:00
Michael Starzinger
2c09760ac4 [turbofan] Re-enable test that no longer fails.
This enables tests which rely on the context available at "debugger"
statements to be accurate. This is the case by now when deoptimization
information is available.

R=yangguo@chromium.org
BUG=v8:4055

Review URL: https://codereview.chromium.org/2129123002 .

Cr-Commit-Position: refs/heads/master@{#37604}
2016-07-08 09:52:07 +00:00
jgruber
d49d3864d7 [builtins] Construct builtin frame in String/Number ctors
BUG=v8:5173
R=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/2118283003
Cr-Commit-Position: refs/heads/master@{#37598}
2016-07-08 06:38:19 +00:00
ben
1f53e42bd6 Handle symbols in FrameMirror#invocationText().
Fix a TypeError when putting together the invocationText for a symbol
method's stack frame.

See https://github.com/nodejs/node/issues/7536.

Review-Url: https://codereview.chromium.org/2122793003
Cr-Commit-Position: refs/heads/master@{#37597}
2016-07-07 21:32:03 +00:00
franzih
2f36ee7176 [builtins] Migrate SharedArrayBuffer.byteLength to C++.
Drive-by-fix: hydrogen code does not blindly return the
byteLength offset, instead it executes what is defined
in the byteLength getter.

BUG=

Review-Url: https://codereview.chromium.org/2123263002
Cr-Commit-Position: refs/heads/master@{#37595}
2016-07-07 19:44:23 +00:00
mstarzinger
b3b1bf279a [turbofan] Context in debugger is accurate by now.
This enables tests which rely on the context available at "debugger"
statements to be accurate. This is the case by now when deoptimization
information is available.

R=mvstanton@chromium.org
BUG=v8:4035

Review-Url: https://codereview.chromium.org/2125773005
Cr-Commit-Position: refs/heads/master@{#37590}
2016-07-07 14:26:52 +00:00
mstarzinger
67efc381b0 [turbofan] Re-enable tests that no longer fail.
R=mvstanton@chromium.org

Review-Url: https://codereview.chromium.org/2127093002
Cr-Commit-Position: refs/heads/master@{#37589}
2016-07-07 13:40:00 +00:00
mstarzinger
07612e0d35 [test] Remove obsolete mjsunit/call-counts test.
R=mvstanton@chromium.org
BUG=v8:4458

Review-Url: https://codereview.chromium.org/2129903002
Cr-Commit-Position: refs/heads/master@{#37584}
2016-07-07 12:04:11 +00:00
mstarzinger
bae7870c41 [turbofan] Re-enable tests that are not longer too slow.
R=mvstanton@chromium.org

Review-Url: https://codereview.chromium.org/2132503002
Cr-Commit-Position: refs/heads/master@{#37583}
2016-07-07 11:30:15 +00:00
jkummerow
b36237b8a3 [ForIn] Fix HasEnumerableProperty for Proxies with null prototype
BUG=v8:5181

Review-Url: https://codereview.chromium.org/2129563002
Cr-Commit-Position: refs/heads/master@{#37577}
2016-07-07 10:12:06 +00:00
neis
d3aefe8cc3 [parser] Fix bug in for-of desugaring.
When reading the value property of an iterator result fails, we must not close the iterator.
This was not discovered earlier because the tests had a subtle bug.

This CL fixes both the desugaring and the tests.

BUG=

Review-Url: https://codereview.chromium.org/2119353002
Cr-Commit-Position: refs/heads/master@{#37571}
2016-07-07 08:16:13 +00:00
neis
4a4f7175df [parser] Fix bug in destructuring binding for catch.
For variables introduced as part of a catch pattern, we used to set their
"initializer position" to the beginning of the pattern.  This lead to
full-codegen eliminating crucial hole checks when reading such variables
inside the pattern itself.

R=adamk@chromium.org, littledan@chromium.org
BUG=v8:5178

Review-Url: https://codereview.chromium.org/2123953002
Cr-Commit-Position: refs/heads/master@{#37569}
2016-07-07 07:31:16 +00:00
mvstanton
a80164ec43 [TurboFan] Improve Array constructor optimization
And in so doing, enable a handful of excluded tests.

BUG=

Review-Url: https://codereview.chromium.org/2127713003
Cr-Commit-Position: refs/heads/master@{#37559}
2016-07-06 15:17:10 +00:00
mlippautz
9f7fd3a554 [heap] Remove test running OOM on some bots
While the test was useful to reproduce the issue locally it creates a lot of
heap pressure and causes all sorts of troubles (OOM, slowness) on the bots, so
let's drop it.

R=hpayer@chromium.org

Review-Url: https://codereview.chromium.org/2127803002
Cr-Commit-Position: refs/heads/master@{#37551}
2016-07-06 13:09:03 +00:00
mstarzinger
c4781e344c [runtime] Deprecate RUNTIME_ASSERT from debugger methods.
This removes explicit uses of the RUNTIME_ASSERT macro from some runtime
methods. The implicit ones in CONVERT_FOO_ARG_CHECKED will be addressed
in a separate CL for all runtime modules at once.

R=yangguo@chromium.org
BUG=v8:5066

Review-Url: https://codereview.chromium.org/2053573004
Cr-Commit-Position: refs/heads/master@{#37545}
2016-07-06 09:06:58 +00:00
neis
45a8167477 [debugger] Don't leak holes from generator arguments.
This is a quick fix for the hole leaking from generators via the debugger's frame
inspection feature: when collecting the arguments, convert each hole to undefined.
In the long term, we probably want to remember and restore the actual arguments
rather than pushing these dummy arguments on each resume.

BUG=v8:5164

Review-Url: https://codereview.chromium.org/2122923003
Cr-Commit-Position: refs/heads/master@{#37544}
2016-07-06 08:11:29 +00:00
jarin
7614362b7e [turbofan] Set elements kind to holey if constructing array of possibly non-zero length.
BUG=chromium:621147

Review-Url: https://codereview.chromium.org/2126623003
Cr-Commit-Position: refs/heads/master@{#37543}
2016-07-06 07:55:36 +00:00
mlippautz
da3745d8d9 Reland "[heap] Track length for array buffers to avoid free-ing dependency"
The dependency would only happen if we have a smi overflow for the length and
have create a heap number. In this case the heap number would've to survive
until the array buffer is collected.

To avoid this dependency we track the length (as we previously used to).

BUG=chromium:625752
LOG=N
TEST=test/mjsunit/regress/regress-625752.js
R=hpayer@chromium.org

This reverts commit 1791d7bb9a.

Review-Url: https://codereview.chromium.org/2127643002
Cr-Commit-Position: refs/heads/master@{#37537}
2016-07-05 16:32:17 +00:00
machenbach
1791d7bb9a Revert of [heap] Track length for array buffers to avoid free-ing dependency (patchset #2 id:20001 of https://codereview.chromium.org/2122603004/ )
Reason for revert:
[Sheriff] This makes mjsunit/regress/regress-625752 extremely slow on all gc stress bots and leads to timeouts with custom snapshot:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/builds/6602

Original issue's description:
> [heap] Track length for array buffers to avoid free-ing dependency
>
> The dependency would only happen if we have a smi overflow for the length and
> have create a heap number. In this case the heap number would've to survive
> until the array buffer is collected.
>
> To avoid this dependency we track the length (as we previously used to).
>
> BUG=chromium:625748,chromium:625752
> LOG=N
> TEST=test/mjsunit/regress/regress-625752.js
> R=hpayer@chromium.org
>
> Committed: https://crrev.com/ddc75cc1356a58b6cfd63f9da0586e1150496b3d
> Cr-Commit-Position: refs/heads/master@{#37530}

TBR=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:625748,chromium:625752

Review-Url: https://codereview.chromium.org/2127483003
Cr-Commit-Position: refs/heads/master@{#37533}
2016-07-05 14:43:24 +00:00
mlippautz
ddc75cc135 [heap] Track length for array buffers to avoid free-ing dependency
The dependency would only happen if we have a smi overflow for the length and
have create a heap number. In this case the heap number would've to survive
until the array buffer is collected.

To avoid this dependency we track the length (as we previously used to).

BUG=chromium:625748,chromium:625752
LOG=N
TEST=test/mjsunit/regress/regress-625752.js
R=hpayer@chromium.org

Review-Url: https://codereview.chromium.org/2122603004
Cr-Commit-Position: refs/heads/master@{#37530}
2016-07-05 13:15:22 +00:00
yangguo
7a834e8b69 [debugger] add test case for throwing in generators.
R=neis@chromium.org

Review-Url: https://codereview.chromium.org/2117303003
Cr-Commit-Position: refs/heads/master@{#37520}
2016-07-05 10:12:33 +00:00
bmeurer
72275e6620 [intrinsic] Drop the %_ValueOf intrinsic.
This drops the %_ValueOf intrinsic, but keeps the runtime entry
%ValueOf for now, by either migrating the functionality (mostly
Debug mirror or toString/valueOf methods) to C++ or TurboFan
builtins, or switching to the %ValueOf runtime call when it's
not performance critical anyways.

The %_ValueOf intrinsic was one of the last blockers for fixing
the unsound machine operator typing in TurboFan.

R=yangguo@chromium.org
BUG=v8:5049

Committed: https://crrev.com/293bd7882987f00e465710ce468bfb1eaa7d3fa2
Review-Url: https://codereview.chromium.org/2126453002
Cr-Original-Commit-Position: refs/heads/master@{#37512}
Cr-Commit-Position: refs/heads/master@{#37519}
2016-07-05 10:05:40 +00:00
machenbach
0960beb0ef Revert of [intrinsic] Drop the %_ValueOf intrinsic. (patchset #2 id:20001 of https://codereview.chromium.org/2126453002/ )
Reason for revert:
[Sheriff] Breaks without i18n:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20noi18n%20-%20debug/builds/8466

Original issue's description:
> [intrinsic] Drop the %_ValueOf intrinsic.
>
> This drops the %_ValueOf intrinsic, but keeps the runtime entry
> %ValueOf for now, by either migrating the functionality (mostly
> Debug mirror or toString/valueOf methods) to C++ or TurboFan
> builtins, or switching to the %ValueOf runtime call when it's
> not performance critical anyways.
>
> The %_ValueOf intrinsic was one of the last blockers for fixing
> the unsound machine operator typing in TurboFan.
>
> R=yangguo@chromium.org
> BUG=v8:5049
>
> Committed: https://crrev.com/293bd7882987f00e465710ce468bfb1eaa7d3fa2
> Cr-Commit-Position: refs/heads/master@{#37512}

TBR=yangguo@chromium.org,bmeurer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5049

Review-Url: https://codereview.chromium.org/2117273002
Cr-Commit-Position: refs/heads/master@{#37514}
2016-07-05 08:01:06 +00:00
jgruber
971468031a Use toString tag to format receiver in stack traces
This concerns formatting of calls to, e.g., Math.acos in stack traces,
in which the receiver is an object with an attached toString tag. If
such a tag exists, use it to format the receiver typename to ensure that
the stack trace includes 'Math.acos' instead of 'Object.acos'.

R=yangguo@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2110683007
Cr-Commit-Position: refs/heads/master@{#37513}
2016-07-05 07:42:53 +00:00
bmeurer
293bd78829 [intrinsic] Drop the %_ValueOf intrinsic.
This drops the %_ValueOf intrinsic, but keeps the runtime entry
%ValueOf for now, by either migrating the functionality (mostly
Debug mirror or toString/valueOf methods) to C++ or TurboFan
builtins, or switching to the %ValueOf runtime call when it's
not performance critical anyways.

The %_ValueOf intrinsic was one of the last blockers for fixing
the unsound machine operator typing in TurboFan.

R=yangguo@chromium.org
BUG=v8:5049

Review-Url: https://codereview.chromium.org/2126453002
Cr-Commit-Position: refs/heads/master@{#37512}
2016-07-05 06:47:53 +00:00
caitpotter88
8134986917 [builtins] don't create keys for undefined property descriptors in O.gOPDs
Implements the change proposed at https://github.com/tc39/ecma262/pull/593.

In summary, Object.getOwnPropertyDescriptors can produce results which cause
Object.defineProperties() to throw, by inserting a property with an undefined
descriptor into the result object. This change to the algorithm requires that
the descriptor only be added to the result object if it is not undefined.

BUG=v8:4725
R=littledan@chromium.org, adamk@chromium.org, jwolfe@igalia.com

Review-Url: https://codereview.chromium.org/2118613003
Cr-Commit-Position: refs/heads/master@{#37504}
2016-07-04 18:04:05 +00:00
jgruber
f59a23356b [builtins] Add receiver to builtin exit frames
Stack trace generation requires access to the receiver; and while the
receiver is already on the stack, we cannot determine its position
during stack trace generation (it's stored in argv[0], and argc is only
stored in a callee-saved register).

This patch grants access to the receiver by pushing argc onto builtin
exit frames as an extra argument. Compared to simply pushing the
receiver, this requires an additional dereference during stack trace
generation, but one fewer during builtin calls.

BUG=v8:4815

Review-Url: https://codereview.chromium.org/2106883003
Cr-Commit-Position: refs/heads/master@{#37500}
2016-07-04 12:46:47 +00:00
ishell
43aee0331d [fullcode][mips][mips64][ppc][s390] Avoid trashing of a home object when doing a keyed store to a super.
BUG=chromium:625590

Review-Url: https://codereview.chromium.org/2120963002
Cr-Commit-Position: refs/heads/master@{#37497}
2016-07-04 11:42:39 +00:00
ishell
acd674db10 [crankshaft] Use canonical nan_value or minus_zero_value objects instead of constant heap numbers with NaN or -0.0 values.
BUG=chromium:625547

Review-Url: https://codereview.chromium.org/2115413002
Cr-Commit-Position: refs/heads/master@{#37495}
2016-07-04 09:59:26 +00:00
jarin
9fdacb9e55 [turbofan] Better handling of empty type in simplified lowering.
The re-typer now only types a node if its inputs are all typed with the
exception of phi nodes. This works because all cycles in the graph have
to contain a phi node.

BUG=chromium:625558

Review-Url: https://codereview.chromium.org/2120243002
Cr-Commit-Position: refs/heads/master@{#37493}
2016-07-04 08:43:12 +00:00
hablich
9c0aef52fa Revert of Amends the TypedArray constructor to use the path for primitives for all (patchset #4 id:60001 of https://codereview.chromium.org/2096873002/ )
Reason for revert:
Speculative revert to unblock roll https://codereview.chromium.org/2114113002/

Original issue's description:
> Amends the TypedArray constructor to use the path for primitives for all
> types of primitives, not just undefined, booleans, numbers, and strings.
> (The missing cases were null and Symbol.) This is required by the
> specification, and there are test262 tests which we were failing due to
> this bug.
>
> BUG=v8:5124
>
> Committed: https://crrev.com/f788bd9cce19815cba746e47bb65abfe25c16208
> Committed: https://crrev.com/f772c22cd1c492aa0235a8e6012d0386146d2eb2
> Cr-Original-Commit-Position: refs/heads/master@{#37234}
> Cr-Commit-Position: refs/heads/master@{#37407}

TBR=littledan@chromium.org,bakkot@google.com
NOTREECHECKS=true
BUG=v8:5124

Review-Url: https://codereview.chromium.org/2120763002
Cr-Commit-Position: refs/heads/master@{#37487}
2016-07-02 14:53:11 +00:00
caitpotter88
cd9e5f30ea [builtins] make AsyncFunction constructor a subclass of Function
Corrects a small problem with the current implementation of the AsyncFunction
constructor.

See https://tc39.github.io/ecmascript-asyncawait/#async-function-constructor for
details.

BUG=v8:4483
R=littledan@chromium.org, adamk@chromium.org, jwolfe@igalia.com

Review-Url: https://codereview.chromium.org/2118653004
Cr-Commit-Position: refs/heads/master@{#37484}
2016-07-01 22:52:40 +00:00
littledan
0ff7b4830c Implement immutable prototype chains
This patch implements "immutable prototype exotic objects" from the ECMAScript
spec, which are objects whose __proto__ cannot be changed, but are not otherwise
frozen. They are introduced in order to prevent a Proxy from being introduced
to the prototype chain of the global object.

The API is extended by a SetImmutablePrototype() call in ObjectTemplate, which
can be used to vend new immutable prototype objects. Additionally, Object.prototype
is an immutable prototype object.

In the implementation, a new bit is added to Maps to say whether the prototype is
immutable, which is read by SetPrototype. Map transitions to the immutable prototype
state are not saved in the transition tree because the main use case is just for
the prototype chain of the global object, which there will be only one of per
Context, so no need to take up the extra word for a pointer in each full transition
tree.

BUG=v8:5149

Review-Url: https://codereview.chromium.org/2108203002
Cr-Commit-Position: refs/heads/master@{#37482}
2016-07-01 19:20:11 +00:00