Commit Graph

63 Commits

Author SHA1 Message Date
fschneider@google.com df94b27666 VM: Align implementations of assembler constant pools.
Add Support for adding patchable/non-patchable entries on ARM/MIPS like
already done for x64/ARM64.

R=vegorov@google.com

Review URL: https://codereview.chromium.org//886173003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@43589 260f80e4-7a28-3924-810f-c04153c831b5
2015-02-09 11:47:36 +00:00
fschneider@google.com 1e7310d48f Improve constant pool implementation in the assembler.
Instead of using RawObject* as keys, use Object*. Using handles eliminates any assumption
about the underlying GC implementation (e.g. requiring that old objects don't move).

Remove special handling of null_object by making HashMap more generic and
allowing the trait to specify the value used to indicate an empty element.

The goal is to use one unified, efficient implementation of the constant
pool on all architectures that require one (x64, arm64, mips).

R=vegorov@google.com, zra@google.com

Review URL: https://codereview.chromium.org//848703002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@42901 260f80e4-7a28-3924-810f-c04153c831b5
2015-01-15 10:43:36 +00:00
regis@google.com fc919001c5 Improve generated MIPS code for conditional expressions and branches by delaying
emission of comparison code.
Improve instruction tracing in all simulators.

R=zra@google.com

Review URL: https://codereview.chromium.org//817593002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@42555 260f80e4-7a28-3924-810f-c04153c831b5
2014-12-22 20:50:15 +00:00
vegorov@google.com 0e1479d2cb Merge RawICData::range_feedback_ field into RawICData::state_bits_.
We were using a lot of bits in state_bits for recording deoptimization reasons, never asked about presence of those bits.

Ultimately optimizer cares only about 3 different deopts, so most all of those bits were wasted.

R=srdjan@google.com, zra@google.com
BUG=

Review URL: https://codereview.chromium.org//807593002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@42388 260f80e4-7a28-3924-810f-c04153c831b5
2014-12-16 13:12:35 +00:00
vegorov@google.com aa48bd4759 Range feedback for arithmetic operations.
In addition to tracking input and output ranges in the IC-stubs with a Smi fastpath (SmiAdd and SmiSub, currently) this CL also introduces two IC stubs that have no fast-path by still track ranges and update the range feedback.

We are able to distinguish between the following ranges (encoding of the lattice is shown in the parens):

- u-smi  (0000)
- smi    (0001)
- uint31 (0010)
- int32  (0011)
- uint32 (0100)
- int64  (1xxx) and (x1x1)

BUG=
R=fschneider@google.com, srdjan@google.com, zra@google.com

Review URL: https://codereview.chromium.org//735543003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@42370 260f80e4-7a28-3924-810f-c04153c831b5
2014-12-15 18:48:15 +00:00
regis@google.com 0fb9f43f32 Complete and clean up breakpoint support in all 3 debuggers embedded in MIPS,
ARM, and ARM64 simulators.
Implement the same debugging commands in all 3 simulators: stop_sim_at flag, bt,
p icount, break, del, unstop, etc...

R=zra@google.com

Review URL: https://codereview.chromium.org//789903002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@42216 260f80e4-7a28-3924-810f-c04153c831b5
2014-12-09 19:26:26 +00:00
fschneider@google.com 855541d88e Make subtype test stubs isolate-specific.
This avoids loading the current isolate from the context
register and makes those stubs not depend on having the context
stored in the CTX register.

R=vegorov@google.com

Review URL: https://codereview.chromium.org//605533003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40714 260f80e4-7a28-3924-810f-c04153c831b5
2014-09-26 16:06:30 +00:00
iposva@google.com cc13627fc8 - Remove Isolate::CurrentAddress().
- Remove use of INFINITY and -INFINITY.

R=rmacnak@google.com, srdjan@google.com

Review URL: https://codereview.chromium.org//609593002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40700 260f80e4-7a28-3924-810f-c04153c831b5
2014-09-25 23:39:30 +00:00
koda@google.com 667454a233 Support old-space allocation in generated code (bump block only for now).
First steps towards general pretenuring support.
* Generalize Heap::Top/EndAddress.
* Add testing flag to exercise new code paths.
* Also update the slow-case runtime calls, to ensure a fresh block will be allocated in old.

Next steps are general invalidation of the generated code and adding a policy that doesn't blow up the store buffers), and freelist allocation.

Review URL: https://codereview.chromium.org//578443003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40530 260f80e4-7a28-3924-810f-c04153c831b5
2014-09-19 23:46:22 +00:00
fschneider@google.com da0fb6bbe2 More intrinsics in IR.
R=srdjan@google.com, vegorov@google.com, zra@google.com

Review URL: https://codereview.chromium.org//513213002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40088 260f80e4-7a28-3924-810f-c04153c831b5
2014-09-10 13:34:58 +00:00
zra@google.com 5d3f4708ec Fixes to support ARMv5 lego mindstorm.
1. Deopts on division when neither vfp nor idiv are present.
   In a subsequent CL, I can add a leaf runtime call for this.

2. Uses a different PC read offset in STR and STM instructions.
   On ARMv5 and earlier, the PC read offset is 8 except in STR
   and STM instructions, where it is implementation defined. On
   lego mindstorm it is 12. This requires changing
   kEntryPointToPcMarkerOffset to be a function.

3. Uses a dummy struct to compute the size of a compressed
   pc descriptor to avoid alignment issues. sizeof(PcDescriptorRec)
   is 16 on ia32 and arm. Subtracting sizeof(int16_t) gives 14,
   which creates alignment problems on ARM, i.e. poor performance on
   ARMv6 and later, and wrong results on ARMv5 and earlier.

R=regis@google.com

Review URL: https://codereview.chromium.org//467103005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@39250 260f80e4-7a28-3924-810f-c04153c831b5
2014-08-14 15:42:00 +00:00
fschneider@google.com 36c848d1d7 VM: Optimized context allocation on all platforms.
This change generate inline code for context allocation and makes
the stores to initialize the parent pointer and the context variables
explicit in the optimized flow graph. This allows dead store elimination
to eliminate those stores.

Before, we only had inlined context allocation for ia32.

Furthermore:
* Added an assertion that the exit label of slow-path code
is bound when emitting deferred code. This used to cause random crashes
if forgotten.

* Fixed a bug in allocation stats on ARM.

BUG=dartbug.com/17238
R=srdjan@google.com

Review URL: https://codereview.chromium.org//346823003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@39202 260f80e4-7a28-3924-810f-c04153c831b5
2014-08-13 15:49:01 +00:00
vegorov@google.com 36cddbd749 Use shorter TryAllocate instruction sequence on ARM/ARM64/MIPS.
On these architectures it's preferable to load Scavenger address into the register and then access top/end fields through this register instead of loading addresses of those fields as immediates --- which takes either two instructions or a memory load through a pool pointer.

Cleanup boxing slow-paths in the optimizing compiler. We had tons of duplicated code that was essentially doing the same thing.

BUG=
R=johnmccutchan@google.com, regis@google.com

Review URL: https://codereview.chromium.org//410333003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@38539 260f80e4-7a28-3924-810f-c04153c831b5
2014-07-24 12:04:21 +00:00
zra@google.com b73310c2c2 Adds intrinsics for Float64Array [] and []=.
Improves performance in unoptimized code.

R=regis@google.com, srdjan@google.com

Review URL: https://codereview.chromium.org//408373002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@38483 260f80e4-7a28-3924-810f-c04153c831b5
2014-07-22 23:16:07 +00:00
zra@google.com fbbc91ff69 Cleanup of class id loading sequences.
These ended up looking performance neutral, but
the cleanup is probably good.

R=srdjan@google.com, vegorov@google.com

Review URL: https://codereview.chromium.org//392343002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@38333 260f80e4-7a28-3924-810f-c04153c831b5
2014-07-17 16:20:11 +00:00
zra@google.com 3560708738 Removes branches from LoadTaggedClassIdMayBeSmi.
Since this assembler macro is used in the CheckInlineCache stub,
this change improves unoptimized code performance.

R=srdjan@google.com

Review URL: https://codereview.chromium.org//383443002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@38096 260f80e4-7a28-3924-810f-c04153c831b5
2014-07-09 18:31:21 +00:00
asiva@google.com f85f986bda Make isolate specific stub code accessors instance methods instead
of static. This allows use of isolate without having to call
Isolate::Current() when using these accessors.

R=johnmccutchan@google.com, srdjan@google.com, zra@google.com

Review URL: https://codereview.chromium.org//365983002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@38040 260f80e4-7a28-3924-810f-c04153c831b5
2014-07-07 21:25:00 +00:00
zra@google.com 419dce3183 Fixes field access on MIPS for classes with many fields.
This mirrors yesterday's fix for ARM.

R=regis@google.com

Review URL: https://codereview.chromium.org//338353005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@37419 260f80e4-7a28-3924-810f-c04153c831b5
2014-06-17 20:44:24 +00:00
srdjan@google.com e35ecf13e3 Add LoadTaggedClassIdMayBeSmi to assembly and improve performance of inline cache stubs.
R=zra@google.com

Review URL: https://codereview.chromium.org//313083008

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@37011 260f80e4-7a28-3924-810f-c04153c831b5
2014-06-04 20:37:21 +00:00
fschneider@google.com 01255e0843 Change COMPILE_ASSERT to take only one argument and use it in more places.
This way it can be used in the same way as ASSERT.

R=iposva@google.com

Review URL: https://codereview.chromium.org//298963006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@36625 260f80e4-7a28-3924-810f-c04153c831b5
2014-05-26 09:45:04 +00:00
zra@google.com c8dba0e27f Adds assert to mips assembler macros.
The asserts prevent trying to put macros in the
branch delay slot.

R=iposva@google.com

Review URL: https://codereview.chromium.org//268673021

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@35912 260f80e4-7a28-3924-810f-c04153c831b5
2014-05-08 14:41:33 +00:00
regis@google.com 8868058d60 Enums cleanup.
R=iposva@google.com

Review URL: https://codereview.chromium.org//259393002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@35559 260f80e4-7a28-3924-810f-c04153c831b5
2014-04-30 01:26:14 +00:00
fschneider@google.com d6178535b2 Landing: Write protect executable pages in the VM.
Change executable pages to be read/execute but not writable by default.

All pages are made temporarily writable just before a full GC, because both
the mark and sweep phases write to the pages. When allocating in a page and
when patching code, the pages are made temporarily writable.

The order of allocation of Code and Instructions objects is changed so that
a GC will not occur after Instructions is allocated. (A full GC would
render the Instructions unwritable.) A scoped object is used to make memory
protection simpler.

Original CL: https://codereview.chromium.org/106593002/

I added a cc test that is expected to crash.

R=srdjan@google.com

Review URL: https://codereview.chromium.org//136563002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32493 260f80e4-7a28-3924-810f-c04153c831b5
2014-02-10 12:18:06 +00:00
zra@google.com 48017a73cc Fixes ABI bug in MIPS.
Adds test for native extensions with autoscoping set to false.

R=asiva@google.com

Review URL: https://codereview.chromium.org//131103025

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32147 260f80e4-7a28-3924-810f-c04153c831b5
2014-01-29 23:07:50 +00:00
johnmccutchan@google.com 9ca09b50e7 Track live instance and allocation counts for classes.
R=iposva@google.com

Review URL: https://codereview.chromium.org//51653006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@31978 260f80e4-7a28-3924-810f-c04153c831b5
2014-01-22 19:21:22 +00:00
zra@google.com 3fd0e585d3 Fixes bug in far branches on MIPS.
Also increases test coverage of far branches on
ARM and MIPS.

R=regis@google.com

Review URL: https://codereview.chromium.org//107293008

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@31024 260f80e4-7a28-3924-810f-c04153c831b5
2013-12-10 16:43:06 +00:00
asiva@google.com c0ddb83c3b ARM and MIPS changes which correspond to the initial change submitted in
https://codereview.chromium.org/63093003/

R=regis@google.com, zra@google.com

Review URL: https://codereview.chromium.org//62953014

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@30124 260f80e4-7a28-3924-810f-c04153c831b5
2013-11-08 19:40:07 +00:00
fschneider@google.com aa789a7b27 Merge (x & y) == 0 pattern to emit a single test instruction.
This is based on a previous uncommitted CL by vegorov@
(https://codereview.chromium.org/14251023/).

It is rebased and fixes a bug in the MIPS implementation: BranchOnCondition
requires the comparison result in fixed registers CMPRES1/CMPRES2.

Remove register alias TMP1 (=TMP) and CMPRES (=CMPRES1). It is confusing to
have them around and easy to forget that they are actually the same.

R=srdjan@google.com, zra@google.com

Review URL: https://codereview.chromium.org//59613005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@29966 260f80e4-7a28-3924-810f-c04153c831b5
2013-11-06 12:13:29 +00:00
srdjan@google.com 3a8252f90d Cleanups: int -> intptr_t for "array" lengths, memory sizes.
R=asiva@google.com

Review URL: https://codereview.chromium.org//26294002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@28324 260f80e4-7a28-3924-810f-c04153c831b5
2013-10-07 20:19:37 +00:00
fschneider@google.com cfab482b84 Follow-up fix to my change to IsPowerOfTwo: Alignment of one means no alignment, not zero.
We assert that the alignment is a power of two. Therefore, platforms that do not need 
alignment should return alignment of one instead of zero.

R=kmillikin@google.com

Review URL: https://codereview.chromium.org//23745008

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@27037 260f80e4-7a28-3924-810f-c04153c831b5
2013-09-03 10:56:43 +00:00
regis@google.com 8171570100 Fix the previously ineffective assert checking the number of arguments passed to
a runtime entry in the VM.

R=asiva@google.com

Review URL: https://codereview.chromium.org//23672011

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@26826 260f80e4-7a28-3924-810f-c04153c831b5
2013-08-28 23:07:14 +00:00
zra@google.com 5c3c549300 Allows compiler bailout to handle errors of any type.
R=asiva@google.com, iposva@google.com

Review URL: https://codereview.chromium.org//22389004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25974 260f80e4-7a28-3924-810f-c04153c831b5
2013-08-09 19:51:11 +00:00
zra@google.com fa2ad38a31 Enables per-function far-branches for ARM and MIPS.
R=regis@google.com, srdjan@google.com

Review URL: https://codereview.chromium.org//21363003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25723 260f80e4-7a28-3924-810f-c04153c831b5
2013-08-01 20:51:46 +00:00
zra@google.com 42217dc159 Implements far-branches on ARM.
R=regis@google.com

Review URL: https://codereview.chromium.org//21159002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25617 260f80e4-7a28-3924-810f-c04153c831b5
2013-07-30 15:33:36 +00:00
zra@google.com dad3270d95 Implements far branch targets for MIPS.
This change adds a flag --mips-far-branches, which when set causes
relative branches to be converted to absolute branches by determining
the PC, adding the branch offset to it, and using the jr or jalr
instruction to jump if the branch test passes.

This procedure clobbers the assembler temporary TMP, so TMP can no
longer be used in a branch test or in the branch delay slot of a
relative branch. Because TMP can't be used in a branch test, a
new temporary is introduced CMPRES2. This change replaces TMP with
CMPRES1 or another register where TMP can no longer be used.

Tests that were failing due to a too-far relative have the
--mips-far-branches flag set.

R=regis@google.com

Review URL: https://codereview.chromium.org//20369003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25543 260f80e4-7a28-3924-810f-c04153c831b5
2013-07-26 23:30:32 +00:00
zra@google.com 20dcf8afaa Implements OSR for arm and mips.
R=regis@google.com

Review URL: https://codereview.chromium.org//19017007

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24896 260f80e4-7a28-3924-810f-c04153c831b5
2013-07-10 23:45:18 +00:00
regis@google.com 169bc2f989 Fix code for store buffer update on ARM and MIPS (link register was trashed).
R=zra@google.com

Review URL: https://codereview.chromium.org//17868006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24493 260f80e4-7a28-3924-810f-c04153c831b5
2013-06-26 22:14:42 +00:00
regis@google.com 5ffa56b798 Fix and simplify invocation of noSuchMethod on all platforms after the wrong
number (or bad name) of arguments is passed.
The frame of the wrong method (the one invoked with the wrong number or name of
arguments) is not left on the stack and therefore not visible in the stack trace
anymore, which is much cleaner, especially since the leftover frame was not
fully initialized.
This change was already done on ARM.

R=zra@google.com

Review URL: https://codereview.chromium.org//17857008

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24485 260f80e4-7a28-3924-810f-c04153c831b5
2013-06-26 19:58:49 +00:00
zra@google.com 4a99fabecb Enables language tests for SIMMIPS.
R=regis@google.com

Review URL: https://codereview.chromium.org//17131002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24098 260f80e4-7a28-3924-810f-c04153c831b5
2013-06-17 15:58:31 +00:00
zra@google.com c004b84376 Enables more VM tests for SIMMIPS.
Implements:
- Megamorphic instance calls
- Left-shift
- Equality
- and various bug-fixes.

R=regis@google.com

Review URL: https://codereview.chromium.org//15934025

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@23877 260f80e4-7a28-3924-810f-c04153c831b5
2013-06-11 20:08:40 +00:00
zra@google.com e846af4128 Implements intrinsics for MIPS.
Also, adds the MADD, MADDU, MTLO, MTHI instructions
to the MIPS simulator, assembler, and disassembler.

R=regis@google.com

Review URL: https://codereview.chromium.org//16272004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@23489 260f80e4-7a28-3924-810f-c04153c831b5
2013-05-31 21:03:41 +00:00
zra@google.com e6cf04a8bb Changes to run "Hello, world!" on MIPS hardware.
R=regis@google.com

Review URL: https://codereview.chromium.org//16160013

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@23484 260f80e4-7a28-3924-810f-c04153c831b5
2013-05-31 18:41:41 +00:00
zra@google.com 354b204cf0 Enables optimization on MIPS
- Exposes double precision rather than single precision floating point registers
  to architecture generic code. This entails a mechanical change in the assembler
  to floating point instructions.
- Adds slti, sltiu instructions for comparison with small immediates, and uses
  them in the Branch(Un)Signed* macros.
- Fixes a bug in the intermediate language comparison/branching instructions
  caused by using subu for comparison. Now it uses two slt instructions.
- Fixes register use bugs in intermediate language.
- More uses of NULLREG instead of loading Object::null()

R=regis@google.com

Review URL: https://codereview.chromium.org//16022011

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@23190 260f80e4-7a28-3924-810f-c04153c831b5
2013-05-24 23:45:41 +00:00
zra@google.com 3c10f6b796 On MIPS, keeps Object::null() in a register.
On MIPS, we have a lot of registers, and we don't use very many of them.
This change removes the second temporary register TMP2, and instead
dedicates a register to holding Object::null(), which is used frequently
for comparisons, etc..

Also, uses branch delay slot when leaving a dart frame and returning.

R=regis@google.com

Review URL: https://codereview.chromium.org//14854010

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22331 260f80e4-7a28-3924-810f-c04153c831b5
2013-05-02 17:53:34 +00:00
zra@google.com aa2dd0acf7 On MIPS, uses more branch delay slots.
Also, tries to reorganize loops to look like what gcc produces.

R=regis@google.com

Review URL: https://codereview.chromium.org//14733002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22262 260f80e4-7a28-3924-810f-c04153c831b5
2013-05-01 16:56:31 +00:00
zra@google.com 09f3f2537e Uses slt and sltu for signed vs. unsigned comparison by the MIPS assembler.
Previously, the sequence subu/b{gt,le,...}z was used, which fails to
distinguish between signed and unsigned comparison.

R=regis@google.com

Review URL: https://codereview.chromium.org//14556002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22159 260f80e4-7a28-3924-810f-c04153c831b5
2013-04-30 00:35:09 +00:00
zra@google.com a49ab3a890 Adds support for debugger API on MIPS.
Enable debugger api tests on MIPS.
Enable isolate tests on MIPS.
Enable code descriptors tests on MIPS.
Enable snapshot tests on MIPS.
Enable heap tests on MIPS.

Review URL: https://codereview.chromium.org//14284020

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22042 260f80e4-7a28-3924-810f-c04153c831b5
2013-04-25 18:03:15 +00:00
zra@google.com 069456803e Implements features to run "Hello, world!" on simulated MIPS.
Review URL: https://codereview.chromium.org//14246039

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@21759 260f80e4-7a28-3924-810f-c04153c831b5
2013-04-19 18:31:47 +00:00
regis@google.com d79c7c1969 Implement long jump in ARM and MIPS simulators.
Implement error and exception handler stubs on ARM.
Hook up simulator for object tests.
Enable codegen and object tests on ARM.

Review URL: https://codereview.chromium.org//14309004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@21680 260f80e4-7a28-3924-810f-c04153c831b5
2013-04-18 16:23:25 +00:00
zra@google.com 64d10ad4e4 Implements write barrier on MIPS.
Review URL: https://codereview.chromium.org//13925024

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@21532 260f80e4-7a28-3924-810f-c04153c831b5
2013-04-16 00:25:03 +00:00