Commit Graph

1987 Commits

Author SHA1 Message Date
leszeks
537c855882 [ignition] BytecodeGraphBuilder: Merge correct environment in try block
Making new nodes inside of exception-handled blocks fiddles around with the
current environment to merge the exception paths. In particular, the current
environment pointer is mutated. This patch ensures that when we merge the fast
and slow paths of the LdaContextLookup, we actually merge the correct
environment and do not accidentally merge the exceptional environment.

BUG=chromium:651394

Review-Url: https://codereview.chromium.org/2379043002
Cr-Commit-Position: refs/heads/master@{#39878}
2016-09-29 15:18:06 +00:00
verwaest
fecd09ce32 Readd default function variables upon scope reset for preparse abort
BUG=chromium:651327

Review-Url: https://codereview.chromium.org/2380993003
Cr-Commit-Position: refs/heads/master@{#39864}
2016-09-29 13:29:15 +00:00
mtrofin
aff5ab1132 [wasm] fix for GC during instantiation.
BUG=chromium:651070

Review-Url: https://codereview.chromium.org/2371403003
Cr-Commit-Position: refs/heads/master@{#39848}
2016-09-29 04:24:42 +00:00
mtrofin
df490c3484 [wasm] Fix for cloning module heap size value
The module size is encoded as a HeapNumber, and needs to be
explicitly cloned.

BUG=chromium:647649

Review-Url: https://codereview.chromium.org/2347333002
Cr-Commit-Position: refs/heads/master@{#39845}
2016-09-29 00:48:28 +00:00
ishell
8d8c134b12 [ic][mips][mips64] Ensure store handlers return value in proper register.
BUG=chromium:650973

Review-Url: https://codereview.chromium.org/2374003002
Cr-Commit-Position: refs/heads/master@{#39823}
2016-09-28 11:46:44 +00:00
jgruber
da27e0c886 Allow empty first parts of ConsStrings
TurboFan lowering (see [0]) of ConsString creation cannot ensure that
the first part of the cons string is non-empty without introducing a phi
and negatively impacting performance.

This modifies ConsStringIterator to allow empty first parts of
ConsStrings.

BUG=v8:5440

Review-Url: https://codereview.chromium.org/2377983002
Cr-Commit-Position: refs/heads/master@{#39817}
2016-09-28 09:46:56 +00:00
bmeurer
15a449b141 [typedarray] Properly initialize JSTypedArray::length with Smi.
Even after https://codereview.chromium.org/2371963002 we still did not
always store a Smi into the JSTypedArray::length field, the runtime
function %TypedArrayInitializeFromArrayLike was still storing whatever
it got from the JavaScript code, which is highly dependent on internal
decisions of the ICs and the representation selection in the optimizing
compilers, so that's pretty fragile.

R=verwaest@chromium.org
BUG=chromium:650933

Review-Url: https://codereview.chromium.org/2377943002
Cr-Commit-Position: refs/heads/master@{#39802}
2016-09-28 05:49:37 +00:00
jgruber
515994b8ca [regexp] Don't cache exec method in Regexp.proto[@@split]
The call to RegExpSubclassExec may refer to a different exec method
since splitter is newly constructed previously to the call.

BUG=v8:5351

Review-Url: https://codereview.chromium.org/2370733003
Cr-Commit-Position: refs/heads/master@{#39774}
2016-09-27 14:02:33 +00:00
verwaest
c0ded71713 Don't reset parameters if we aborted preparsing, rebuild them from the params_ list
BUG=

Review-Url: https://codereview.chromium.org/2372703004
Cr-Commit-Position: refs/heads/master@{#39769}
2016-09-27 13:05:32 +00:00
jkummerow
142f9dfcad [crankshaft] TypedArrayInitialize: force length to be a Smi
BUG=chromium:650404

Review-Url: https://codereview.chromium.org/2371963002
Cr-Commit-Position: refs/heads/master@{#39744}
2016-09-26 23:00:45 +00:00
verwaest
7f025eb626 Remove ARGUMENTS_VARIABLE and fix crankshaft to properly detect the arguments object and keep it alive when inlining .apply
BUG=

Review-Url: https://codereview.chromium.org/2367483003
Cr-Commit-Position: refs/heads/master@{#39670}
2016-09-23 14:27:02 +00:00
Michael Starzinger
4b2c6d03e4 [turbofan] Add proper type guards to escape analysis.
This makes sure the {EscapeAnalysisReducer} inserts proper {TypeGuard}
nodes if the replacement node is not a subtype of the original node.
This happens predominantly for code that has been made unreachable by
type checks.

R=jarin@chromium.org
TEST=mjsunit/regress/regress-crbug-640497
BUG=chromium:640497

Review URL: https://codereview.chromium.org/2363573003 .

Cr-Commit-Position: refs/heads/master@{#39656}
2016-09-23 11:02:13 +00:00
lpy
68ee0a4f90 Add regression test for crbug.com/648740.
BUG=648740

Review-Url: https://codereview.chromium.org/2362563002
Cr-Commit-Position: refs/heads/master@{#39643}
2016-09-22 20:44:05 +00:00
verwaest
df7ecd1c1a Declare the arguments object before creating the function var, to make sure it masks it
BUG=chromium:649067

Review-Url: https://codereview.chromium.org/2362463003
Cr-Commit-Position: refs/heads/master@{#39642}
2016-09-22 19:16:42 +00:00
gsathya
ba41697cbd [promises] PromiseResolveThenableJob: change then to be a JSReceiver
BUG=v8:649078

Review-Url: https://codereview.chromium.org/2362503003
Cr-Commit-Position: refs/heads/master@{#39609}
2016-09-21 23:56:20 +00:00
mstarzinger
b097c6c4f1 [turbofan] Support for ConsString by escape analysis.
This add support for ConsString objects allocated inline to the escape
analysis pass. The raw hash field in such strings needs special handling
similar to existing raw fields. This also contains materialization code
within the deoptimizer as usual.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-648737
BUG=chromium:648737

Review-Url: https://codereview.chromium.org/2357153002
Cr-Commit-Position: refs/heads/master@{#39594}
2016-09-21 12:30:00 +00:00
cbruni
2fd6d6093e [elements] Handlify raw parameter_map pointers for SloppyArgumentsAccessor
Handlify pointers in IncludesValueImpl and DirectCollectElementIndicesImpl.

BUG=chromium:648373

Review-Url: https://codereview.chromium.org/2354773006
Cr-Commit-Position: refs/heads/master@{#39586}
2016-09-21 10:22:53 +00:00
mstarzinger
81f4342994 [turbofan] Remove bogus constant materialization from frame.
This removes an optimization from the code generator that tries to
materialize certain constants (i.e. context and closure) from the
stackframe when possible. This does not work with Harmony tail calls
which are split into several instructions. There have already been
numerous bugs in this optimization, it is too fragile in its current
form.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-648539
BUG=chromium:648539

Review-Url: https://codereview.chromium.org/2357583003
Cr-Commit-Position: refs/heads/master@{#39583}
2016-09-21 09:31:32 +00:00
littledan
dcd61b9020 Filter out synthetic variables from with scopes
This patch ensures that variables like .new_target aren't overwritable
using with scopes. It does this by ensuring that scope analysis does
not consider with scopes (or eval scopes) for such 'synthetic variables',
similarly to how the 'this' variable was already handled.
The patch also adds a DCHECK for the dynamic parallel to this case,
replacing a previous unreachable path for a particular instance.

BUG=v8:5405

Review-Url: https://codereview.chromium.org/2353623002
Cr-Commit-Position: refs/heads/master@{#39567}
2016-09-20 22:14:54 +00:00
littledan
bd078193a0 Remove synthetic unresolved variables from async/await desugaring
This patch uses temporaries rather than unresolved variables for
.promise and .debug_is_active. For .promise, a new field is added
to the FunctionState, similarly to .generator_object. This change
fixes a bug where .promise was locally shadowable by with, affecting
program semantics.

BUG=v8:5405

Review-Url: https://codereview.chromium.org/2359513002
Cr-Commit-Position: refs/heads/master@{#39566}
2016-09-20 21:31:32 +00:00
mstarzinger
4dab7b5a1d [turbofan] Fix loop assignment analysis on ForInStatements.
The implicit assignment to the induction variable in a ForInStatement
has been ignored by the AST loop assignment analysis. This was hidden
for cases where the parser introduced a ".for" temporary, but triggers
when the variable is declared outside the loop.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-647887
BUG=chromium:647887

Review-Url: https://codereview.chromium.org/2356733002
Cr-Commit-Position: refs/heads/master@{#39551}
2016-09-20 12:37:33 +00:00
bmeurer
d86038db25 [crankshaft] Protect against deopt loops from string length overflows.
Crankshaft just unconditionally deoptimizes the code when the length of
a string addition result would overflow. In order to protect against
deopt loops we insert a global protector cell.

We will use the same mechanism for inlining certain string additions
into TurboFan as well, and protecting against overflow (we will also
extend this to deal with String.prototype.concat and friends once we
get there).

BUG=v8:5404
R=jarin@chromium.org,hpayer@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.v8:v8_linux64_msan_rel

Committed: https://crrev.com/cb19257a926a55209a6d6858ce26d51a0447ba71
Review-Url: https://codereview.chromium.org/2348293002
Cr-Original-Commit-Position: refs/heads/master@{#39511}
Cr-Commit-Position: refs/heads/master@{#39525}
2016-09-20 05:59:35 +00:00
machenbach
53510f6a80 Revert of [crankshaft] Protect against deopt loops from string length overflows. (patchset #1 id:1 of https://codereview.chromium.org/2348293002/ )
Reason for revert:
Mean https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20arm64%20-%20sim%20-%20MSAN/builds/10910

Original issue's description:
> [crankshaft] Protect against deopt loops from string length overflows.
>
> Crankshaft just unconditionally deoptimizes the code when the length of
> a string addition result would overflow. In order to protect against
> deopt loops we insert a global protector cell.
>
> We will use the same mechanism for inlining certain string additions
> into TurboFan as well, and protecting against overflow (we will also
> extend this to deal with String.prototype.concat and friends once we
> get there).
>
> BUG=v8:5404
> R=jarin@chromium.org,hpayer@chromium.org
>
> Committed: https://crrev.com/cb19257a926a55209a6d6858ce26d51a0447ba71
> Cr-Commit-Position: refs/heads/master@{#39511}

TBR=hpayer@chromium.org,jarin@chromium.org,bmeurer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5404

Review-Url: https://codereview.chromium.org/2357433002
Cr-Commit-Position: refs/heads/master@{#39518}
2016-09-19 21:50:15 +00:00
bmeurer
cb19257a92 [crankshaft] Protect against deopt loops from string length overflows.
Crankshaft just unconditionally deoptimizes the code when the length of
a string addition result would overflow. In order to protect against
deopt loops we insert a global protector cell.

We will use the same mechanism for inlining certain string additions
into TurboFan as well, and protecting against overflow (we will also
extend this to deal with String.prototype.concat and friends once we
get there).

BUG=v8:5404
R=jarin@chromium.org,hpayer@chromium.org

Review-Url: https://codereview.chromium.org/2348293002
Cr-Commit-Position: refs/heads/master@{#39511}
2016-09-19 21:01:30 +00:00
mtrofin
7d008c0d1b [wasm] moved regression test under test/mjsunit/regression/wasm
We'd like wasm regressions to live under a subfolder of the mjsunit
regression folder.

BUG=

Review-Url: https://codereview.chromium.org/2344373002
Cr-Commit-Position: refs/heads/master@{#39483}
2016-09-17 00:29:10 +00:00
mstarzinger
c2cf8b11ed [turbofan] Handle stack overflow during inlining.
This handles the case where generating bytecode for inlining purposes
causes a stack overflow. We just abort inlining but also need to clear
pending exceptions.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-647217
BUG=chromium:647217

Review-Url: https://codereview.chromium.org/2339383002
Cr-Commit-Position: refs/heads/master@{#39448}
2016-09-15 14:05:13 +00:00
mstarzinger
b848716c98 [compiler] Fix confusion about OSR BailoutId semantics.
The semantics of the {BailoutId} representing an OSR entry point is
different between the interpreter and the full code generator. These
semantics are hard-coded in various graph builders. We need to ensure
that the correct graph builder is chosen for OSR compilations.

R=rmcilroy@chromium.org
TEST=mjsunit/regress/regress-5380
BUG=v8:5380

Review-Url: https://codereview.chromium.org/2341663002
Cr-Commit-Position: refs/heads/master@{#39444}
2016-09-15 11:00:42 +00:00
jgruber
8df547d402 [regexp] Avoid unneeded accesses to lastIndex
This implements https://github.com/tc39/ecma262/pull/627/.

BUG=v8:5360

Review-Url: https://codereview.chromium.org/2339443002
Cr-Commit-Position: refs/heads/master@{#39402}
2016-09-14 07:39:44 +00:00
mstarzinger
85289749f4 [interpreter] Add regression test for bogus OSR entry.
This adds a regression test for a bug where {OsrPoll} instructions
within the bytecode stream ended up outside of actual loops. This has
been fixed already, by merging {OsrPoll} into the backwards branch.

R=rmcilroy@chromium.org
TEST=mjsunit/regress/regress-crbug-645888
BUG=chromium:645888

Review-Url: https://codereview.chromium.org/2337033002
Cr-Commit-Position: refs/heads/master@{#39385}
2016-09-13 13:23:21 +00:00
mvstanton
2ab3fcf42f Record call counts also for megamorphic calls.
To make better inlining decisions, it's good to have call counts for poly/mega-morphic cases. This CL makes it work for calls, and another will follow to better unify the code between constructor calls and normal calls (and thence, to record megamorphic call counts there as well).

BUG=

Review-Url: https://codereview.chromium.org/2325083003
Cr-Commit-Position: refs/heads/master@{#39377}
2016-09-13 11:04:22 +00:00
cbruni
621f4af720 [elements] Handlify SloppyArguments IndexOfValueImpl
The raw pointer to the parameter_map might get stale in case of accessors present on
the arguments object.
Drive-by-fix: use nullptr instead of the_hole with isolate access.

BUG=chromium:645680

Review-Url: https://codereview.chromium.org/2332503002
Cr-Commit-Position: refs/heads/master@{#39359}
2016-09-12 17:32:09 +00:00
adamk
58325e616d [turbofan] Switch from a whitelist to a blacklist for NeedsFrameStateInput
The whitelist is populated with those inline intrinsics that are lowered
in JSIntrinsicInlining and were not previously blacklisted. Thus the only
additional FrameStates this CL adds are those where the caller tries to
call the INLINE version of an intrinsic but ends up calling the RUNTIME
version instead.

R=bmeurer@chromium.org
BUG=chromium:644631

Review-Url: https://codereview.chromium.org/2331543002
Cr-Commit-Position: refs/heads/master@{#39357}
2016-09-12 16:12:57 +00:00
mstarzinger
0681deb914 [interpreter] Fix destroyed new.target register use.
This fixes a corner-case where the bytecode was using the <new.target>
register directly without going through the local variable. The value
might be clobbered because the deoptimizer doesn't properly restore the
value. The label will causes bytecode pipeline to be flushed and hence
ensure {BytecodeRegisterOptimizer} doesn't reuse <new.target> anymore.

R=rmcilroy@chromium.org
TEST=mjsunit/regress/regress-crbug-645103
BUG=chromium:645103

Review-Url: https://codereview.chromium.org/2325133002
Cr-Commit-Position: refs/heads/master@{#39306}
2016-09-09 12:20:20 +00:00
adamk
e4273007b6 Properly handle holes following spreads in array literals
Before this change, the spread desugaring would naively call
`%AppendElement($R, the_hole)` and in some cases $R would have
a non-holey elements kind, putting the array into the bad state
of exposing holes to author code.

This patch avoids calling %AppendElement with a hole, instead
simply incrementing $R.length when it sees a hole in the literal
(this is safe because $R is known to be an Array). The existing
logic for elements transitions takes care of giving the array a
holey ElementsKind.

BUG=chromium:644215

Review-Url: https://codereview.chromium.org/2321533003
Cr-Commit-Position: refs/heads/master@{#39294}
2016-09-08 18:50:41 +00:00
mstarzinger
9984d6f689 [deoptimizer] Support materialization of ContextExtension.
This adds support to the deoptimizer to materialize ContextExtension
objects that have been de-materialized by escape analysis. This is
follow-up to the inline allocation of such objects during the create
lowering phase (i.e. JSCreateWithContext and JSCreateCatchContext).

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-644245
BUG=chromium:644245

Review-Url: https://codereview.chromium.org/2317353003
Cr-Commit-Position: refs/heads/master@{#39270}
2016-09-08 10:33:20 +00:00
bmeurer
4ed27fc836 [turbofan] Ensure that all prototypes are stable for push/pop.
When lowering Array.prototype.push/.pop to the fast inlined version, we
first need to ensure that all prototypes (including the Object.prototype)
are stable.

R=mvstanton@chromium.org
BUG=chromium:644689

Review-Url: https://codereview.chromium.org/2319533005
Cr-Commit-Position: refs/heads/master@{#39266}
2016-09-08 08:48:32 +00:00
bmeurer
91ed540ee6 [turbofan] Revert "Avoid overflow checks on SpeculativeNumberAdd/Subtract/Multiply."
The optimization is not correct for unsigned output types, and we the
overall complexity seems too high. We need to find a better way to
take into account the input/output type restrictions.

Also added a regression test for the unsigned output bug.

BUG=v8:5267,v8:5270,v8:5357
TBR=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2320013002
Cr-Commit-Position: refs/heads/master@{#39262}
2016-09-08 04:20:31 +00:00
lpy
7a38b927c8 Reland - Allow lexically declared "arguments" in function scope in sloppy mode.
Lexically declared "arguments" in sloppy mode will throw redeclaration error
currently, this patch fixes it by delaying the declaration of arguments until we
fully parse parameter list and function body.

BUG=v8:4577
LOG=N

Committed: https://crrev.com/70a613dd0a5f5d205b46559b55702764464851fa
Review-Url: https://codereview.chromium.org/2290753003
Cr-Original-Commit-Position: refs/heads/master@{#39109}
Cr-Commit-Position: refs/heads/master@{#39230}
2016-09-07 06:54:54 +00:00
mstarzinger
553d504923 [turbofan] Handle ObjectIsReceiver in escape analysis.
This adds handling of {IrOpcode::kObjectIsReceiver} nodes to the escape
status analysis. Such uses are treated as escaping for now until we add
dedicated handling to the escape analysis reducer.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-631027
BUG=chromium:631027

Review-Url: https://codereview.chromium.org/2317623003
Cr-Commit-Position: refs/heads/master@{#39205}
2016-09-06 11:59:31 +00:00
rmcilroy
c950256013 [Turbofan] Fix CallSuper argument order in BytecodeGraphBuilder.
The constructor and new.target arguments were passed to CallConstruct in
the wrong order by BytecodeGraphBuilder, which caused subclassing to be
incorrect when optimizing from bytecode.

Also clean up some unecessary functions in interpreter.cc found while
figuring this out.

BUG=chromium:642409

Review-Url: https://codereview.chromium.org/2312103002
Cr-Commit-Position: refs/heads/master@{#39204}
2016-09-06 11:53:19 +00:00
mstarzinger
cc1249b779 [compiler] Bytecode preparation fails for asm.js modules.
This handles the case where preparation of bytecode might fail inside
Compiler::EnsureBytecode due to the underlying function being a fully
validated asm.js module. We simply bailout of bytecode preparation.

R=bradnelson@chromium.org
TEST=mjsunit/regress/regress-crbug-644111
BUG=chromium:644111

Review-Url: https://codereview.chromium.org/2309853002
Cr-Commit-Position: refs/heads/master@{#39187}
2016-09-05 23:03:07 +00:00
jgruber
64c518d06d Do not include Error.captureStackTrace in the trace
BUG=v8:5342

Review-Url: https://codereview.chromium.org/2307783002
Cr-Commit-Position: refs/heads/master@{#39124}
2016-09-02 09:51:42 +00:00
bmeurer
86af343749 [test] Add regression test for http://crbug.com/642056.
The bug itself was already fixed in ToT as part of
http://crrev.com/2263273003.

R=machenbach@chromium.org
BUG=chromium:642056

Review-Url: https://codereview.chromium.org/2306913002
Cr-Commit-Position: refs/heads/master@{#39117}
2016-09-02 07:08:29 +00:00
machenbach
d67fedb12c Revert of Allow lexically declared "arguments" in function scope in sloppy mode. (patchset #5 id:100001 of https://codereview.chromium.org/2290753003/ )
Reason for revert:
Breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/9470

Original issue's description:
> Allow lexically declared "arguments" in function scope in sloppy mode.
>
> Lexically declared "arguments" in sloppy mode will throw redeclaration error
> currently, this patch fixes it by delaying the declaration of arguments until we
> fully parse parameter list and function body.
>
> BUG=v8:4577
> LOG=N
>
> Committed: https://crrev.com/70a613dd0a5f5d205b46559b55702764464851fa
> Cr-Commit-Position: refs/heads/master@{#39109}

TBR=adamk@chromium.org,mythria@chromium.org,lpy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4577

Review-Url: https://codereview.chromium.org/2304853002
Cr-Commit-Position: refs/heads/master@{#39115}
2016-09-02 06:23:57 +00:00
lpy
70a613dd0a Allow lexically declared "arguments" in function scope in sloppy mode.
Lexically declared "arguments" in sloppy mode will throw redeclaration error
currently, this patch fixes it by delaying the declaration of arguments until we
fully parse parameter list and function body.

BUG=v8:4577
LOG=N

Review-Url: https://codereview.chromium.org/2290753003
Cr-Commit-Position: refs/heads/master@{#39109}
2016-09-01 22:10:34 +00:00
bmeurer
432790c92c [turbofan] Only check semantic axis for Type::None.
R=jarin@chromium.org
BUG=chromium:643073

Review-Url: https://codereview.chromium.org/2299903002
Cr-Commit-Position: refs/heads/master@{#39065}
2016-09-01 07:11:21 +00:00
bmeurer
64a7bd3877 [turbofan] Don't treat the hole NaN as constant inside the compiler.
We use a signaling NaN to represent the hole in
FAST_HOLEY_DOUBLE_ELEMENTS backing stores, but on Intel processors, the
C++ compiler may decide to (or be forced to due to calling conventions)
use X87 registers for double values. However transfering to X87
registers automatically quietens the NaNs and there's no way to disable
this. Therefore we should just always load the hole NaN from the canonical
place identified by the address_of_hole_nan external reference instead,
which might even be more efficient in some cases.

R=jarin@chromium.org, jkummerow@chromium.org
BUG=v8:5332

Review-Url: https://codereview.chromium.org/2303643002
Cr-Commit-Position: refs/heads/master@{#39062}
2016-09-01 06:02:19 +00:00
bmeurer
7b79224b21 [crankshaft] Disable further folding already folded allocations.
When we try to further fold previously folded allocations in Crankshaft
GVN we don't properly transform the allocations involved, which causes
the mechanism to leave holes in the new/old space (and thereby violate
the iterability property of the new/old space).

BUG=chromium:621868
R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2297983003
Cr-Commit-Position: refs/heads/master@{#39040}
2016-08-31 09:48:45 +00:00
bmeurer
864cdc124c [test] Speed-up regression test for growing stores.
TBR=machenbach@chromium.org
BUG=chromium:635798,chromium:638295

Review-Url: https://codereview.chromium.org/2288813003
Cr-Commit-Position: refs/heads/master@{#38991}
2016-08-30 04:04:32 +00:00
littledan
5af4cd9840 Disallow tail calls from async functions and generators
Tail calls don't make sense from async functions and generators, as
each activation of these functions needs to make a new, distnict,
non-reused generator object. These tail calls are not required per
spec. This patch disables both syntactic and implicit tail calls
in async functions and generators.

R=neis
BUG=v8:5301,chromium:639270

Review-Url: https://codereview.chromium.org/2278413003
Cr-Commit-Position: refs/heads/master@{#38986}
2016-08-29 18:31:35 +00:00