Commit Graph

31422 Commits

Author SHA1 Message Date
neis
552ba59eb2 [compiler] Remove bailout in ast-numbering's VisitYield.
It's sufficient to bailout when seeing that the function literal is a
generator or async function, as those are the only cases in which there can be
yields.

Also: add a comment on --turbo-from-bytecode and Ignition generators.

R=mstarzinger@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2060843002
Cr-Commit-Position: refs/heads/master@{#36930}
2016-06-13 12:56:35 +00:00
nikolaos
cdec5e8d26 Remove erroneous DCHECK related to expression classifiers
It seems that I forgot to remove the DCHECK when refactoring this
function, even though the comment had it right.  It also seems that
this is hard to trigger.  The minimal example I found, after fuzzer's
bug, was:

   eval, x[eval]

R=adamk@chromium.org
BUG=chromium:619476
LOG=N

Review-Url: https://codereview.chromium.org/2058413002
Cr-Commit-Position: refs/heads/master@{#36929}
2016-06-13 12:34:19 +00:00
mstarzinger
f002cee0db [compiler] Remove dead disabling of optimizations.
The AstNumberingVisitor is by now strictly running after we allocated
the SharedFunctionInfo. This removes some left-over code from before
that invariant was holding.

R=mvstanton@chromium.org

Review-Url: https://codereview.chromium.org/1965803002
Cr-Commit-Position: refs/heads/master@{#36928}
2016-06-13 12:31:23 +00:00
mstarzinger
689be6e49d [arm] Fix typo in FastNewRestParameterStub::Generate.
TBR=bmeurer@chromium.org
BUG=chromium:619538

Review-Url: https://codereview.chromium.org/2066493002
Cr-Commit-Position: refs/heads/master@{#36927}
2016-06-13 12:28:14 +00:00
jkummerow
31ca317af3 [--runtime-call-stats] Fix ACCESSOR handler computation
When running with FLAG_runtime_call_stats, native accessor accesses must
go through the runtime for accurate accounting. Previously the slow_stub()
was used as a handler in order to accomplish this, but it could never be
looked up from the code cache successfully due to mismatched code flags,
which could cause more handler recompilations than in normal operation.
This patch fixes that by emitting a runtime call into the compiled
handler instead of using the slow_stub().

Drive-by cleanup: drop the unused StoreIC_Megamorphic builtin.

Review-Url: https://codereview.chromium.org/2054133002
Cr-Commit-Position: refs/heads/master@{#36926}
2016-06-13 12:14:18 +00:00
machenbach
51f14c56c6 Revert of [wasm] Refactor function name table and lookup (patchset #2 id:20001 of https://codereview.chromium.org/2057523002/ )
Reason for revert:
[Sheriff] Speculative revert for flaky gc stress crashes, e.g.:
https://build.chromium.org/p/client.v8/builders/V8%20Mac%20GC%20Stress/builds/6592
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/builds/6143

Original issue's description:
> [wasm] Refactor function name table and lookup
>
> The function name table will now always be set; a CHECK will fail if
> the length would exceed the integer range.
> Also, the resolution of undefined function names to "<WASM UNNAMED>" is
> moved over to the wasm side.
>
> R=titzer@chromium.org
>
> Committed: https://crrev.com/3400ee9f4f21a455b7850ec42a4182a3c0eba310
> Cr-Commit-Position: refs/heads/master@{#36918}

TBR=titzer@chromium.org,clemensh@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2062793002
Cr-Commit-Position: refs/heads/master@{#36925}
2016-06-13 11:46:34 +00:00
mstarzinger
471f6baf95 [compiler] Move generator optimization heuristics.
This moves the decision whether to optimize generator or async functions
into the AstNumberingVisitor. Optimization heuristics that are based on
the function source should be encapsulated in this class.

R=neis@chromium.org

Review-Url: https://codereview.chromium.org/2065543002
Cr-Commit-Position: refs/heads/master@{#36924}
2016-06-13 11:43:28 +00:00
cbruni
33b8bc24a1 Revert of Replace all remaining Oddball checks with new function (patchset #10 id:180001 of https://codereview.chromium.org/2043183003/ )
Reason for revert:
failing tests

Original issue's description:
> Replace all remaining Oddball checks with new function
>
> This CL removes the IsUndefined() and Co. methods from Object and HeapObject.
> The new method all take the isolate as parameter.
>
> BUG=
>
> Committed: https://crrev.com/ccefb3ae5fe967288d568013fb04e8761eafebc5
> Cr-Commit-Position: refs/heads/master@{#36921}

TBR=mstarzinger@chromium.org,verwaest@chromium.org,yangguo@chromium.org,ahaas@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review-Url: https://codereview.chromium.org/2060213002
Cr-Commit-Position: refs/heads/master@{#36923}
2016-06-13 11:40:35 +00:00
mstarzinger
30f8d33543 [fullcodegen] Factor out VisitRegExpLiteral from architectures.
This makes the aforementioned visitation function independent of the
target architecture by leveraging existing abstractions.

R=mvstanton@chromium.org

Review-Url: https://codereview.chromium.org/2060173002
Cr-Commit-Position: refs/heads/master@{#36922}
2016-06-13 11:01:39 +00:00
cbruni
ccefb3ae5f Replace all remaining Oddball checks with new function
This CL removes the IsUndefined() and Co. methods from Object and HeapObject.
The new method all take the isolate as parameter.

BUG=

Review-Url: https://codereview.chromium.org/2043183003
Cr-Commit-Position: refs/heads/master@{#36921}
2016-06-13 10:21:02 +00:00
cbruni
8a88fc142f [arrays] Fix %GetArrayKeys for special element kinds
Array.prototype.sort would not work properly on sloppy arguments of size > 2.

BUG=chromium:618613

Review-Url: https://codereview.chromium.org/2051413004
Cr-Commit-Position: refs/heads/master@{#36920}
2016-06-13 10:07:03 +00:00
mvstanton
1473226569 Machine-readable TurboFan compiler statistics
We'd like to track performance metrics in an automated way. This CL introduces
--turbo-stats-nvp which exposes --turbo-stats information in {"name"=value} pair
format.

BUG=

Review-Url: https://codereview.chromium.org/2053383002
Cr-Commit-Position: refs/heads/master@{#36919}
2016-06-13 09:35:49 +00:00
clemensh
3400ee9f4f [wasm] Refactor function name table and lookup
The function name table will now always be set; a CHECK will fail if
the length would exceed the integer range.
Also, the resolution of undefined function names to "<WASM UNNAMED>" is
moved over to the wasm side.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2057523002
Cr-Commit-Position: refs/heads/master@{#36918}
2016-06-13 09:32:54 +00:00
mstarzinger
e95cfafb67 Fix arguments object stubs for large arrays.
This fixes FastNewStrictArgumentsStub and FastNewRestParameterStub to no
longer assume that the strict arguments object being allocated will fit
into new-space. The case where said object needs to move to large object
space is now handled in the runtime.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-614727
BUG=chromium:614727

Review-Url: https://codereview.chromium.org/2054853002
Cr-Commit-Position: refs/heads/master@{#36917}
2016-06-13 08:25:43 +00:00
bmeurer
89d8c57b9c [builtins] Introduce proper Float64Atan and Float64Atan2 operators.
Import base::ieee754::atan() and base::ieee754::atan2() from fdlibm and
introduce Float64Atan and Float64Atan2 TurboFan operators based on those,
similar to what we already did for Float64Log and Float64Log1p. Rewrite
Math.atan() and Math.atan2() as TurboFan builtin and use the operators
to also inline Math.atan() and Math.atan2() into optimized TurboFan functions.

R=yangguo@chromium.org
BUG=v8:5086,v8:5095

Review-Url: https://codereview.chromium.org/2065503002
Cr-Commit-Position: refs/heads/master@{#36916}
2016-06-13 07:08:17 +00:00
ishell
2ef6862e5d [builtins] Turn LoadIC_Miss and LoadIC_Slow builtins to TurboFan code stubs.
Review-Url: https://codereview.chromium.org/2033423002
Cr-Commit-Position: refs/heads/master@{#36915}
2016-06-13 07:08:16 +00:00
bmeurer
7ceed92ac0 [builtins] Introduce proper Float64Log1p operator.
Import base::ieee754::log1p() from fdlibm and introduce a Float64Log1p
TurboFan operator based on that, similar to what we do for Float64Log.
Rewrite Math.log1p() as TurboFan builtin and use that operator to also
inline Math.log1p() into optimized TurboFan functions.

Also unify the handling of the special IEEE 754 functions somewhat in
the TurboFan backends. At some point we can hopefully express this
completely in the InstructionSelector (once we have an idea what to do
with the ST(0) return issue on IA-32/X87).

Drive-by-fix: Add some more test coverage for the log function.

R=yangguo@chromium.org
BUG=v8:5086,v8:5092

Review-Url: https://codereview.chromium.org/2060743002
Cr-Commit-Position: refs/heads/master@{#36914}
2016-06-13 05:48:02 +00:00
bmeurer
b01622c312 [ieee754] Import ANSIfied msun log from FreeBSD.
Instead of manually adopting the ancient fdlibm sources, import the msun
versions from FreeBSD instead, which were already adopted to ANSI C.
Still under the same copyright.

R=yangguo@chromium.org
BUG=v8:5065,v8:5086

Review-Url: https://codereview.chromium.org/2065473002
Cr-Commit-Position: refs/heads/master@{#36913}
2016-06-13 04:38:18 +00:00
mtrofin
8e1ccba3b0 [turbofan] Retiring Greedy Allocator
We were able to achieve our goals for register allocation independent of
the allocation algorithm. Performance data so far is inconclusive re. the
value of the Greedy algorithm, compared to the particular Linear Scan
implementation we're currently using, and the performance measurement
techniques we currently use are too imprecise to help with this matter.

Retiring the algorithm to lower maintenance and evolution cost (e.g. lower
cost of adding aliasing support). Once we improve benchmarking stability,
and establish a suite sensitive enough for codegen improvement studies,
we may revive the algorithm, should the need arise.

BUG=

Review-Url: https://codereview.chromium.org/2060673002
Cr-Commit-Position: refs/heads/master@{#36912}
2016-06-13 04:24:12 +00:00
mtrofin
8c1ba59aee RelocInfo modes were not propagated when computing
MemoryOperands, on IA32. This needed to be fixed so that we can
compile wasm code before creating instances, since the compiled code
needs to be patched up for memory and globals references.

This surfaces in asm-to-wasm scenarios.

Added testing (rather, enhanced existing tests).
Note patch#1 where we fail on ia32, and patch#2 with the fix.

BUG=v8:5072

Review-Url: https://codereview.chromium.org/2061583002
Cr-Commit-Position: refs/heads/master@{#36911}
2016-06-13 04:21:16 +00:00
bmeurer
35f5b3dca4 Revert of Add a trace-event for each runtime-stats timer (patchset #6 id:100001 of https://codereview.chromium.org/2052523002/ )
Reason for revert:
Seems to break TSAN, see http://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/10057

Original issue's description:
> The trace-events will have a high overhead when turned on, but they are in a disabled-by-default category.
>
> As long as the off overhead is negligible, this CL allows us to understand the behavior of V8 rather than its performance at the moment.
>
> BUG=v8:5089
>
> Committed: https://crrev.com/44ec143f26769bd103662643bfeafc7d0834cc90
> Cr-Commit-Position: refs/heads/master@{#36909}

TBR=cbruni@chromium.org,fmeawad@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5089

Review-Url: https://codereview.chromium.org/2064553002
Cr-Commit-Position: refs/heads/master@{#36910}
2016-06-13 04:21:15 +00:00
fmeawad
44ec143f26 The trace-events will have a high overhead when turned on, but they are in a disabled-by-default category.
As long as the off overhead is negligible, this CL allows us to understand the behavior of V8 rather than its performance at the moment.

BUG=v8:5089

Review-Url: https://codereview.chromium.org/2052523002
Cr-Commit-Position: refs/heads/master@{#36909}
2016-06-12 16:21:16 +00:00
v8-autoroll
2fc6d926c3 Update V8 DEPS.
Rolling v8/build to ea70305807f935b36a930586aa08c66bfc6fbf8d

Rolling v8/tools/mb to 649b5791b19e4ed3df0c5542b23950d34ca8f3e7

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

Review-Url: https://codereview.chromium.org/2063593002
Cr-Commit-Position: refs/heads/master@{#36908}
2016-06-12 03:25:30 +00:00
peria
7a3150d13d Make String::CanMakeExternal ignore the length of new strings.
It is expected that temporarily used strings die while they are
in new heap.  So we can avoid to pay a heavy cost to externalize
them.  If they are used for times, externalization will happen
when they move to an old heap.

BUG=chrmoium:606093

Review-Url: https://codereview.chromium.org/2046933002
Cr-Commit-Position: refs/heads/master@{#36907}
2016-06-11 05:13:08 +00:00
v8-autoroll
3469d72d04 Update V8 DEPS.
Rolling v8/build to e3d91384eb1f9ee5d3a26ad790f87fc51f3cfc61

Rolling v8/tools/clang to 7f07c3fce21f45df52cf39f0f52277d19b7e3573

Rolling v8/tools/mb to ad1b97c34985d6c464b5b74e75c7c9ec9716fec2

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

Review-Url: https://codereview.chromium.org/2057403004
Cr-Commit-Position: refs/heads/master@{#36906}
2016-06-11 03:24:51 +00:00
gsathya
604445b55b Parser: reuse has_extends, instead of doing a check again
Review-Url: https://codereview.chromium.org/2053393004
Cr-Commit-Position: refs/heads/master@{#36905}
2016-06-11 01:22:36 +00:00
jyan
d86458b1bc S390: [stubs] Remove N-argument Hydrogen-based Array constructor stub
Port c8ac0d8693

Original commit message:

    Instead, always tail call to the runtime. Also, cleanup the various versions
    of the runtime call that is used for Array construction fallback. There can be
    only one.

R=danno@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com, bjaideep@ca.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2060483002
Cr-Commit-Position: refs/heads/master@{#36904}
2016-06-10 19:43:44 +00:00
littledan
5d7b9ece16 Async/await event listener test
This patch adds a test for async/await analogous to a previous Promise test.
It also fixes a typo in promise.js and makes a previous Promise test more
correct by ensuring that all assertions run before completion, fixing the
test expectations for the real result (which seems correct).

BUG=v8:4483
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review-Url: https://codereview.chromium.org/2037653002
Cr-Commit-Position: refs/heads/master@{#36903}
2016-06-10 19:15:35 +00:00
jyan
87ccb1d8af S390: Remove more dead code now that legacy const is gone
Port 757221e574

Original commit message:

    Neither globals nor lookup slots can be hole-initialized anymore, thus
    removing some dead code from the code generators and runtime-scopes.

R=adamk@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com, bjaideep@ca.ibm.com
BUG=

Review-Url: https://codereview.chromium.org/2060473002
Cr-Commit-Position: refs/heads/master@{#36902}
2016-06-10 19:12:23 +00:00
bjaideep
7f6f6ad1ba PPC: [stubs] Remove N-argument Hydrogen-based Array constructor stub
Port c8ac0d8693

Original commit message:

    Instead, always tail call to the runtime. Also, cleanup the various versions
    of the runtime call that is used for Array construction fallback. There can be
    only one.

R=danno@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=chromium:608675
LOG=N

Review-Url: https://codereview.chromium.org/2057253002
Cr-Commit-Position: refs/heads/master@{#36901}
2016-06-10 18:03:13 +00:00
bjaideep
c7cddee678 PPC: Move hashmap into src/base.
Port 2fd55667a6

Original commit message:

    We ported hashmap.h into libsampler as a workaround before, so the main focus of
    this patch is to reduce code duplication. This patch moves the hashmap into
    src/base as well as creates DefaultAllocationPolicy using malloc and free.

R=lpy@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=v8:5050
LOG=N

Review-Url: https://codereview.chromium.org/2057263002
Cr-Commit-Position: refs/heads/master@{#36900}
2016-06-10 17:54:39 +00:00
bjaideep
817dcf2819 PPC: Remove more dead code now that legacy const is gone
Port 757221e574

Original commit message:

    Neither globals nor lookup slots can be hole-initialized anymore, thus
    removing some dead code from the code generators and runtime-scopes.

R=adamk@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2061443002
Cr-Commit-Position: refs/heads/master@{#36899}
2016-06-10 17:54:38 +00:00
alph
3282b515e9 Make use of std::map for profiler code map.
Review-Url: https://codereview.chromium.org/2047243002
Cr-Commit-Position: refs/heads/master@{#36898}
2016-06-10 16:40:24 +00:00
nikolaos
dfb8d3331e Reduce the memory footprint of expression classifiers
This patch attempts to reduce the (stack) memory footprint of
expression classifiers.  Instead of keeping space in each
classifier for all possible error messages that will
(potentially) be reported, if an expression turns out to be
a pattern or a non-pattern, such error messages are placed in
a list shared by the FunctionState and each classifier keeps a
couple of indices in this list.  This requires that classifiers
are used strictly in a stack-based fashion, which is also in line
with my previous patch for revisiting non-pattern rewriting.

R=adamk@chromium.org
BUG=chromium:528697

Review-Url: https://codereview.chromium.org/1708193003
Cr-Commit-Position: refs/heads/master@{#36897}
2016-06-10 16:37:19 +00:00
neis
6e700b7f76 [interpreter] Fix debug stepping for generators.
In commit b3bfc0bd58, I corrected the source
position of yield-exceptions by not setting the "return position" on returns
that correspond to yields. It turns out that this caused a bug with debug
stepping. The proper fix is to keep the return position on those returns but
additionally attach the yield's source position to the Throw emitted in
VisitYield.

R=rmcilroy@chromium.org, yangguo@chromium.org
BUG=v8:4907

Review-Url: https://codereview.chromium.org/2051783002
Cr-Commit-Position: refs/heads/master@{#36896}
2016-06-10 13:30:20 +00:00
neis
6899f878ac [generators] Improve a test.
R=mstarzinger@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2056283002
Cr-Commit-Position: refs/heads/master@{#36895}
2016-06-10 13:27:27 +00:00
ulan
29b695ef13 Tune the memory pressure handler to perform a second GC immediately
after the first GC if time allows and there is memory to be freed.

BUG=chromium:618958
LOG=NO

Review-Url: https://codereview.chromium.org/2057103002
Cr-Commit-Position: refs/heads/master@{#36894}
2016-06-10 13:18:47 +00:00
cbruni
102cb061e1 [tools] Fix Callstats-Group classifier regexp in callstats.py
BUG=

Review-Url: https://codereview.chromium.org/2058003002
Cr-Commit-Position: refs/heads/master@{#36893}
2016-06-10 13:18:46 +00:00
ahaas
6c3d43766e [wasm] Turn on parallel compilation by default.
This CL sets the default value of the flag wasm_num_compilation_tasks to 10.
The actual number of compilation tasks is the minimum of the flag value and
V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads(), which is 8
on my machine.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2054093002
Cr-Commit-Position: refs/heads/master@{#36892}
2016-06-10 12:00:42 +00:00
jkummerow
3b87e9aa03 Fix stale IC::receiver_map_ after prototype fastification
BUG=chromium:618845

Review-Url: https://codereview.chromium.org/2058063002
Cr-Commit-Position: refs/heads/master@{#36891}
2016-06-10 11:43:33 +00:00
yangguo
6f6f1f62ea [snapshot] make snapshot sink a non-dynamic member of the serializer.
R=vogelheim@chromium.org

Review-Url: https://codereview.chromium.org/2052433003
Cr-Commit-Position: refs/heads/master@{#36890}
2016-06-10 11:26:54 +00:00
oth
235ed54a16 [interpreter] Compilation fix for operand scale on ARM builder.
TBR=rmcilroy@chromium.org
BUG=v8:4280
LOG=N

Review-Url: https://codereview.chromium.org/2056243002
Cr-Commit-Position: refs/heads/master@{#36889}
2016-06-10 11:26:53 +00:00
danno
c8ac0d8693 [stubs] Remove N-argument Hydrogen-based Array constructor stub
Instead, always tail call to the runtime. Also, cleanup the various versions
of the runtime call that is used for Array construction fallback. There can be
only one.

BUG=chromium:608675
LOG=N

Review-Url: https://codereview.chromium.org/2024253002
Cr-Commit-Position: refs/heads/master@{#36888}
2016-06-10 11:01:55 +00:00
yangguo
75aada429e [snapshot] pass arguments as pointers, not references.
R=vogelheim@chromium.org

Review-Url: https://codereview.chromium.org/2051043003
Cr-Commit-Position: refs/heads/master@{#36887}
2016-06-10 10:59:04 +00:00
jarin
b4274ce38e [turbofan] Fix bad merge.
TBR=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/2057063002
Cr-Commit-Position: refs/heads/master@{#36886}
2016-06-10 10:42:20 +00:00
oth
85882a6320 [interpreter] Remove OperandScale from front stages of pipeline.
BUG=v8:4280
LOG=N

Review-Url: https://codereview.chromium.org/2041913002
Cr-Commit-Position: refs/heads/master@{#36885}
2016-06-10 10:36:38 +00:00
rmcilroy
4ff921bc27 [Interpreter] Update Blink TestExpectationsIgnition.
Remove expectations which were failing due to eager compilation now that we compile lazily in Ignition, and add intersection-observer/observer-exceptions.html which has recently started failing.

BUG=v8:5096
TBR=machenbach@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2053323002
Cr-Commit-Position: refs/heads/master@{#36884}
2016-06-10 10:33:29 +00:00
cbruni
01a423e00f [--prof] Adding support for RuntimeCallTimerScope based tick separation
BUG=

Review-Url: https://codereview.chromium.org/2050713002
Cr-Commit-Position: refs/heads/master@{#36883}
2016-06-10 09:16:42 +00:00
asaka
8c1b2623cc Replace std::trunc() with trunc() to support cross-compiling
Fix-up of https://codereview.chromium.org/1965443003 required for
certain toolchains that do not support std::trunc().

BUG=

Review-Url: https://codereview.chromium.org/2056693002
Cr-Commit-Position: refs/heads/master@{#36882}
2016-06-10 08:01:47 +00:00
jarin
2890137bdc [turbofan] Introduce PlainPrimitiveToNumber.
This should solve the problem with missing checkpoints after JSToNumber
(PlainPrimitiveToNumber is marked no-write, so the frame-state
propagation should see through it.)

Unfortunately, this also duplicates the word32- and float64-truncation
magic that we have for JSToNumber in "simplified lowering".

Review-Url: https://codereview.chromium.org/2059653002
Cr-Commit-Position: refs/heads/master@{#36881}
2016-06-10 07:45:23 +00:00