It turns out that some old polyfill library uses
RegExp.prototype.flags as a way of feature testing. It's not clear
how widespread this is. For now, as a minimal workaround, we can
return undefined from getters like RegExp.prototype.global when
the receiver is RegExp.prototype. This patch implements that strategy
but omits a UseCounter to make backports easier.

R=adamk
CC=yangguo@chromium.org
BUG=chromium:581577
LOG=Y
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1640803003

Cr-Commit-Position: refs/heads/master@{#34201}

In ES2016, the Proxy enumerate trap is removed. This patch changes
for-in iteration on Proxies to use the ownKeys trap. Due to the clean
organization of that code, the patch basically consists of deletions.

R=adamk
LOG=Y
BUG=v8:4768

Review URL: https://codereview.chromium.org/1717893002

Cr-Commit-Position: refs/heads/master@{#34200}

This patch makes ArraySpeciesCreate fast in V8 by avoiding two property reads
when the following conditions are met:
- No Array instance has had its __proto__ reset
- No Array instance has had a constructor property defined
- Array.prototype has not had its constructor changed
- Array[Symbol.species] has not been reset

For subclasses of Array, or for conditions where one of these assumptions is
violated, the full lookup of species is done according to the ArraySpeciesCreate
algorithm. Although this is a "performance cliff", it does not come up in the
expected typical use case of @@species (Array subclassing), so it is hoped that
this can form a good start. Array subclasses will incur the slowness of looking
up @@species, but their use won't slow down invocations of, for example,
Array.prototype.slice on Array base class instances.

Possible future optimizations:
- For the fallback case where the assumptions don't hold, optimize the two
  property lookups.
- For Array.prototype.slice and Array.prototype.splice, even if the full lookup
  of @@species needs to take place, we still could take the rest of the C++
  fastpath. However, to do this correctly requires changing the calling convention
  from C++ to JS to pass the @@species out, so it is not attempted in this patch.

With this patch, microbenchmarks of Array.prototype.slice do not suffer a
noticeable performance regression, unlike their previous 2.5x penalty.

TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1689733002

Cr-Commit-Position: refs/heads/master@{#34199}

Port e032a98d

R=yangguo@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:4690
LOG=N

Review URL: https://codereview.chromium.org/1721673003

Cr-Commit-Position: refs/heads/master@{#34198}

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1716293002

Cr-Commit-Position: refs/heads/master@{#34197}

The Proxy enumerate trap and Reflect.enumerate are removed from the
ES2016 draft specification. This patch removes the Reflect.enumerate
function, and a follow-on patch will be responsible for the Proxy
trap changes.

R=adamk
LOG=Y
BUG=v8:4768

Review URL: https://codereview.chromium.org/1721453002

Cr-Commit-Position: refs/heads/master@{#34196}

In theory, a user could define the Symbol.isConcatSpreadable property
somewhere in the TypedArray class hierarchy. Array.prototype.concat
optimizes for this case and has templated code for fast concat over
TypedArrays. However, the default environment doesn't have this
property set (it would probably not be web-compatible) and there isn't
clear demand for this optimization. This patch removes that
special-case code.

R=adamk

Review URL: https://codereview.chromium.org/1720533003

Cr-Commit-Position: refs/heads/master@{#34195}

Floating point param and return registers should be within the
compiler's allocatable set.

TEST=cctest/test-run-wasm-js/Run_Float64Add_jswrapped
R=titzer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1714223002

Cr-Commit-Position: refs/heads/master@{#34194}

Local testing suggests that optimized builds add more speed
without trading off tool usability. We get the following
differences (A: non-optimized build, B: optimized):

Sometimes: Lines instrumented in A (covered and uncovered) are not instrumented in B.
Rarely: Lines instrumented and covered in A are instrumented, but not covered in B.

The latter might simply be caused by timing differences in
the two builds.

BUG=chromium:568949
LOG=n
NOTRY=true

Review URL: https://codereview.chromium.org/1719923002

Cr-Commit-Position: refs/heads/master@{#34193}

Currently AllocationSite skips the weak_next pointer in IterateBody and IsValidSlot.

This is not correct because the weak_next is a valid slot in AllocationSite.

BUG=

Review URL: https://codereview.chromium.org/1719903002

Cr-Commit-Position: refs/heads/master@{#34192}

This picks the record-write stub depending on the correct remembered set
action parameter. For values known to be maps we can guarantee that they
never reside in new-space, hence store buffer recording can be skipped.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1716163003

Cr-Commit-Position: refs/heads/master@{#34191}

R=mstarzinger@chromium.org, rmcilroy@chromium.org
BUG=v8:4690
LOG=N

Review URL: https://codereview.chromium.org/1703453002

Cr-Commit-Position: refs/heads/master@{#34190}

This removes a restriction from full-codegen that limited the usability
of the --debug-code flag to only no-snap configurations. The reasoning
for the restriction would still hold, if we ever put full-codegen code
into the snapshot, which we don't. Also there already are several places
in full-codegen that queried the FLAG_debug_code directly, a more
reliable mechanism will be needed if we snapshot full code.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1722593002

Cr-Commit-Position: refs/heads/master@{#34189}

BUG=chromium:587574
LOG=NO

Review URL: https://codereview.chromium.org/1705183003

Cr-Commit-Position: refs/heads/master@{#34188}

The InstructionSelector now associates an effect level to every node in a block.

The effect level of a node is the number of non-eliminatable nodes encountered from the beginning of the block to the node itself.

With this change, on ia32 and x64, a load from memory into a register can be replaced by a memory operand if all of the following conditions hold:

1. The only use of the load is in a 32 or 64 bit word comparison.
2. The user node and the load node belong to the same block.
3. The values of the operands have the same size (i.e., no need to zero-extend or sign-extend the result of the load).

BUG=

Review URL: https://codereview.chromium.org/1706763002

Cr-Commit-Position: refs/heads/master@{#34187}

BUG=

Review URL: https://codereview.chromium.org/1718953002

Cr-Commit-Position: refs/heads/master@{#34186}

BUG= https://code.google.com/p/v8/issues/detail?id=4203
TEST=mjsunit/asm-wasm
R=aseemgarg@chromium.org,titzer@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1720773002

Cr-Commit-Position: refs/heads/master@{#34185}

Rolling v8/third_party/icu to e466f6ac8f60bb9697af4a91c6911c6fc4aec95f

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

Review URL: https://codereview.chromium.org/1715283002

Cr-Commit-Position: refs/heads/master@{#34184}

  The CL #33996 (https://codereview.chromium.org/1695283002) exposed one hidden bug in x87 crankshaft code generation for LCodeGen::DoMathMinMax().

  This CL fixed this bug.

BUG=

Review URL: https://codereview.chromium.org/1715263002

Cr-Commit-Position: refs/heads/master@{#34183}

  port ba2077aa (r34136)

  original commit message:
  Move the already existing fast case for %NewObject into a dedicated
  FastNewObjectStub that we can utilize in places where we would otherwise
  fallback to %NewObject immediately, which is rather expensive.

  Also use FastNewObjectStub as the generic implementation of JSCreate,
  which should make constructor inlining based on SharedFunctionInfo (w/o
  specializing to a concrete closure) viable soon.

BUG=

Review URL: https://codereview.chromium.org/1717203002

Cr-Commit-Position: refs/heads/master@{#34182}

R=binji@chromium.org,bradnelson@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1717993002

Cr-Commit-Position: refs/heads/master@{#34181}

Embedders don't use d8.cc.  Move gdbjit initialization to api.cc.

BUG=

Review URL: https://codereview.chromium.org/1710253002

Cr-Commit-Position: refs/heads/master@{#34180}

Rolling v8/tools/clang to a8adb78c8eda9bddb2aa9c51f3fee60296de1ad4

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

Review URL: https://codereview.chromium.org/1717953002

Cr-Commit-Position: refs/heads/master@{#34179}

Up until now we were unable to (re)optimize code when we hit
uninitialized (Keyed)Load/StoreICs in the code. We always put an IC
there (sharing the feedback vector with fullcodegen at least) and called
it a day. But we never deoptimized the code object when we gathered more
feedback. This doesn't work very well in practice, esp. with hot code
relying on this. So until we have a proper mechanism to express the need
to reoptimize after we gathered additional feedback from optimized code,
we follow the Crankshaft approach instead and install a SOFT deopt, so
we can not only learn but also utilize the new feedback.

R=mstarzinger@chromium.org
BUG=v8:4470
LOG=n

Review URL: https://codereview.chromium.org/1518013002

Cr-Commit-Position: refs/heads/master@{#34178}

Slots filtering of left-trimmed arrays assume that two-pointer fillers are not marked.

BUG=chromium:585787
LOG=NO
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1720623002

Cr-Commit-Position: refs/heads/master@{#34177}

BUG=

Review URL: https://codereview.chromium.org/1522573002

Cr-Commit-Position: refs/heads/master@{#34176}

WASM compiler test will sometimes generate invalid instructions for
DINS/INS.

BUG=

Review URL: https://codereview.chromium.org/1709633004

Cr-Commit-Position: refs/heads/master@{#34175}

Most libraries use `JSON.stringify` with all three arguments [1] to allow for
configuration, even if `replacer` and `space` are falsey, causing the
optimized native stringifying to be missed. This commit allows for the common
case where `replacer` and `space` are not used to be fast.

[1]: https://github.com/hapijs/hapi/pull/3014

BUG=v8:4730
LOG=N

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1710933002

Cr-Commit-Position: refs/heads/master@{#34174}

Rolling v8/tools/clang to 50fc8b6e785aa002218d67b78db871b21b1c9d71

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

Review URL: https://codereview.chromium.org/1710263004

Cr-Commit-Position: refs/heads/master@{#34173}

This was changed to match Annex B.2.5.1 of ES2015 and Firefox in
https://chromium.googlesource.com/v8/v8/+/469d9bfa, but website
breakage was seen in M49 Beta. JSC still returns undefined here.

BUG=chromium:585775
LOG=y
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1714903004

Cr-Commit-Position: refs/heads/master@{#34172}

This was previously reverted due to breakage in devtools, but that has
been worked around in https://codereview.chromium.org/1666573002.

The feature has been publicly-announced as deprecated for several months,
and Chrome 49 will emit deprecation warnings in the console for
uses of the API. This CL aims to remove it from M50 (which is what the
message warns of).

BUG=chromium:552100
LOG=y
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1711863003

Cr-Commit-Position: refs/heads/master@{#34171}

This is a rework of the instanceof operator to support ES6 semantics
(as per section 12.10.4 of the spec:
https://tc39.github.io/ecma262/#sec-instanceofoperator).

It's behind flag --harmony-instanceof for now, which is turned on for staging.

BUG=v8:4447
LOG=N

Review URL: https://codereview.chromium.org/1692713005

Cr-Commit-Position: refs/heads/master@{#34170}

Port ba2077aa

Original commit message:
    Move the already existing fast case for %NewObject into a dedicated
    FastNewObjectStub that we can utilize in places where we would otherwise
    fallback to %NewObject immediately, which is rather expensive.

    Also use FastNewObjectStub as the generic implementation of JSCreate,
    which should make constructor inlining based on SharedFunctionInfo (w/o
    specializing to a concrete closure) viable soon.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1714123002

Cr-Commit-Position: refs/heads/master@{#34169}

BUG=559304
LOG=N

Review URL: https://codereview.chromium.org/1709873002

Cr-Commit-Position: refs/heads/master@{#34168}

This new callback is similar to CallCompletedCallback, but is executed before the call has been made.
Added Isolate* parameter to CallCompletedCallback, marking previous one as deprecated.

BUG=chromium:585949
LOG=Y

Review URL: https://codereview.chromium.org/1689863002

Cr-Commit-Position: refs/heads/master@{#34167}

Adds a profiling counter to each BytecodeArray object, and adds
code to Jump and Return bytecode handlers to update this
counter by the size of the jump or the distance from the return
to the start of the function. This is more accurate than fullcodegen's
approach since it takes forward jumps into account as well as back-edges.

Modifies RuntimeProfiler to track ticks for interpreted frames.
Currently we use the SharedFunctionInfo::profiler_ticks() instead
of adding another to tick field to avoid adding another field to
BytecodeArray since SharedFunctionInfo::profiler_ticks() is only
used by Crankshaft otherwise so we shouldn't need both for

BUG=v8:4689
LOG=N

Review URL: https://codereview.chromium.org/1707693003

Cr-Commit-Position: refs/heads/master@{#34166}

We cannot omit flag check with kPointersToHereAreInterestingMask for maps because incremental marker dynamically sets and clears the flag.

BUG=chromium:587004
LOG=NO

Review URL: https://codereview.chromium.org/1714513003

Cr-Commit-Position: refs/heads/master@{#34165}

--pool-type=int and double have now been merged into number.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1717633002

Cr-Commit-Position: refs/heads/master@{#34164}

BUG=

Review URL: https://codereview.chromium.org/1711813003

Cr-Commit-Position: refs/heads/master@{#34163}

of non-pattern expressions, according to the (internally circulated)
design document.  Details to be provided here.

1.  RewritableAssignmentExpression has been renamed to RewritableExpression.
    It is a wrapper for AST nodes that wait for some potential rewriting
    (that may or may not happen).  Also, Is... and As... macros now see
    through RewritableExpressions.

2.  The function state keeps a list of rewritable expressions that must be
    rewritten only if they are used as non-pattern expressions.

3.  Expression classifiers are now templates, parameterized by parser
    traits.  They keep some additional state: a pointer to the list of
    non-pattern rewritable expressions.  It is important that expression
    classifiers be used strictly in a stack fashion, from now on.

4.  The RewriteNonPattern function has been simplified.

BUG=chromium:579913
LOG=N

Committed: https://crrev.com/7f5c864a6faf2b957b7273891e143b9bde35487c
Cr-Commit-Position: refs/heads/master@{#34154}

Review URL: https://codereview.chromium.org/1702063002

Cr-Commit-Position: refs/heads/master@{#34162}