The declaration of the ToBoolean class moved to the platform-independent part
and its implementations are now structurally very similar. This is just an
intermediate cleanup step to add type recording at the call site.
Note that the MIPS implementation has not really been touched, so it should
continue to work, too.
Review URL: http://codereview.chromium.org/7218012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8359 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
* AST Expression nodes get a separate testing ID to record type info in
ToBooleanStub later. This is necessary to avoid clashes with other uses of
already existing IDs.
* In order to avoid threading the condition expression through tons of places,
TestContexts carry it now with them. Note that we will probably only need the
testing ID of the expression, but having the whole thing at hand makes
debugging easier. Probably we will change this later...
Review URL: http://codereview.chromium.org/7046073
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8274 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This change makes the number of successors of a control instruction
configurable with a template parameter and changes the existing instructions
to use it.
To iterate over all successors I added an iterator instead of always calling
First- and SecondSuccessor.
Review URL: http://codereview.chromium.org/7114004
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8262 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Introduce separate maps for function and with contexts. Use the function
context map for testing whether a context is a function context (global
contexts are no longer function contexts).
Split the paths for allocating with and catch contexts.
Rename some functions. Generally refactor code to make it simpler.
R=ager@chromium.org
BUG=
TEST=
Review URL: http://codereview.chromium.org/7003058
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8231 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Mainly, there were errors concerning blank lines before and after class access
control sections [whitespace/blank_line].
BEFORE an access control section (e.g. public:, private:) there should be a
blank line (except for the section right after the class declaration).
AFTER an access control section there should be no blank line.
TBR=ager@chromium.org
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8193 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The Advance() function of the class responsible for iterating
environment uses didn't always advance as far as it could (relying on
the HasNext predicate to finish advancing). This is brittle.
The HasNext predicate also didn't advance as far as it could when it
was at the end of an environment level. This is a bug.
R=jkummerow@chromium.org
BUG=
TEST=
Review URL: http://codereview.chromium.org/6993023
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8181 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
If type-feedback indicates that an expression was never executed in
the non-optimized code, we insert a forced deoptimization right away
to enable re-optimization if we ever hit this path.
With this change we still continue to build the graph. As a next step, we
should remove the dead code after the deoptimize.
I had to remove one assert about the optimization status in a test since
we now immediately deoptimize after exiting the loop that triggers OSR.
Also remove a restriction that control-flow from an inlined function in a
test context always reaches both true- and false-target.
Review URL: http://codereview.chromium.org/7105015
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8140 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Introduce a class JSReceiver, that is a common superclass of JSObject and
JSProxy. Use JSReceiver where appropriate (probably lots of places that we
still have to migrate, but we will find those later with proxy test suite).
- Move appropriate methods to JSReceiver class (SetProperty,
GetPropertyAttribute, Get/SetPrototype, Lookup, and so on).
- Introduce new JSFunctionProxy subclass of JSProxy. Currently only a stub.
- Overhaul enum InstanceType:
* Introduce FIRST/LAST_SPEC_OBJECT_TYPE that ranges over all types that
represent JS objects, and use that consistently to check language types.
* Rename FIRST/LAST_JS_OBJECT_TYPE and FIRST/LAST_FUNCTION_CLASS_TYPE
to FIRST/LAST_[NON]CALLABLE_SPEC_OBJECT_TYPE for clarity.
* Eliminate the overlap over JS_REGEXP_TYPE.
* Also replace FIRST_JS_OBJECT with FIRST_JS_RECEIVER, but only use it where
we exclusively talk about the internal representation type.
* Insert JS_PROXY and JS_FUNCTION_PROXY in the appropriate places.
- Fix all checks concerning classification, especially for functions, to
use the CALLABLE_SPEC_OBJECT range (that includes funciton proxies).
- Handle proxies in SetProperty (that was the easiest part :) ).
- A few simple test cases.
R=kmillikin@chromium.org
Review URL: http://codereview.chromium.org/6992072
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8126 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
* Centralized AND/OR handling, keeping related code together.
* Removed HandleExpression/HandleInNonTestContext and introduced VisitInSameContext instead, making it more obvious what's actually going on.
* Consistently use a new context when visiting the left sub-expression of an AND/OR. Note that the context stacks in the full code generator and crankshaft are still a bit out of sync for the right sub-expression.
Review URL: http://codereview.chromium.org/6976028
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8124 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The approach is to handle the common case in the optimizing
compiler and to bailout for the rare corner cases.
This is done by initializing all local const-variables with
the hole value and disallowing any use of the hole value statically.
Review URL: http://codereview.chromium.org/6026006
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8104 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Only IA32 version for now. I'll start porting.
Strict mode functions are to get 'undefined' as the receiver when
called with an implicit receiver. Modes are bad! It forces us to have
checks on all function calls.
This change attempts to limit the cost by passing information about
whether or not a call is with an implicit or explicit receiver in ecx
as part of the calling convention. The cost is setting ecx on all
calls and checking ecx on entry to strict mode functions.
Implicit/explicit receiver state has to be maintained by ICs. Various
stubs have to not clobber ecx or save and restore it.
CallFunction stub needs to check if the receiver is implicit when it
doesn't know from the context.
Review URL: http://codereview.chromium.org/7039036
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8040 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Bit tests with a memory operand should be avoided on Intel processors.
On Atom bts with a memory operand has 10~11 cycles latency and on Core 2
it has 5~6 cycles latency, and also produces multiple uops.
If the bit base operand is a register the latency is 1 cycle instead.
This CL improves several cases from Kraken 1.1 benchmark on Atom. For example,
12% for imaging-desaturate, 8% for audio-fft, and 5% for audio-beat-detection.
Review URL: http://codereview.chromium.org//7048003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7987 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
When the stub return a heap number we do a state transition to
a version HEAP_NUMBER that can handle -0.
There is room for further improvement in the typefeedback for the
case of -0. This change however does not address this and only fixes
the acute issue.
Review URL: http://codereview.chromium.org/7037025
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7944 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Better support for 'polymorphic' JS and external arrays
Allow keyed store/load stubs to switch between external array and fast JS arrays without forcing a state transition to the generic stub.
There CL consists of two pieces of functionality. First, code stubs for fast element arrays don't immediately transition to the MEGAMORPHIC state when there's a map mismatch. Second, two ICs are cached per map for fast elements, the MONOMORPHIC version, and a new MEGAMORPHIC version that handles two or more different maps and dispatches to shared stubs to perform the array operation.
Review URL: http://codereview.chromium.org/7036016
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7935 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
As a side note, this change has some positive impact on the performace, e.g. imaging-darkroom is 8.3% faster and ws-ieee754conv is even 19.9% faster. No idea why the speedup is so big in some cases, but never look a gift horse in the mouth... ;-)
Review URL: http://codereview.chromium.org/7042004
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7926 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Allow keyed store/load stubs to switch between external array and fast JS arrays without forcing a state transition to the generic stub.
There CL consists of two pieces of functionality. First, code stubs for fast element arrays don't immediately transition to the MEGAMORPHIC state when there's a map mismatch. Second, two ICs are cached per map for fast elements, the MONOMORPHIC version, and a new MEGAMORPHIC version that handles two or more different maps. Currently, the only array types supported by the MEGAMORPHIC stub are fast elements for objects and JSArrays.
BUG=
TEST=
Review URL: http://codereview.chromium.org/6894003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7917 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The profiler did not correctly identify when there was a JS frame
on the stack after an exception was thrown.
I also refactored the code to use PopTryHandler macro-instructions on all platforms
BUG=73722
TEST=No more valgrind errors related to v8::internal::StackFrameIterator.
Review URL: http://codereview.chromium.org/7019010
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7910 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
1) Add new type JSProxy for representing proxy objects.
Currently devoid of functionality, i.e., all properties are undefined.
2) Some rudimentary global $Proxy functions to create proxies.
Next step: Hook up getProperty and getOwnProperty handlers. Will probably
require introducing a new LookupResult type, which is a mixture of
INTERCEPTOR (handles any property) and CALLBACK (calls back to JS).
Can we unify this somehow?
TODO: Should probably rename existing Proxy type to something like
"Foreign", to avoid confusion.
Review URL: http://codereview.chromium.org/6932068
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7887 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This is IA32 only for now.
Added a random value to each assembler instance (JIT cookie) to be used for constant splitting. Added safe versions of setting a register with an immediate value and for pushing an immediate value. Used these functions where user controlled immediate values could be emitted in the code stream. I also used it for immediates which are an argument number even though the number of formal arguments is currently limited to 16k.
I found no compares directly with user controlled constants.
I am not sure whether the test is that useful, but it might catch some changes missing constant splitting.
Review URL: http://codereview.chromium.org//7005031
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7868 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This allows us to get rid of totally fake LAST_STRING_TYPE and makes
it possible to test for symbols.
I considered splitting HCheckInstanceType into two instructions, but
it seems nice to be able to hide the instance type implementation
details from the hydrogen level.
Review URL: http://codereview.chromium.org/6964011
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
If the result of an fast elements load is converted to an untagged
representation we can omit the hole check if the value is not used
anywhere else except for HChange instructions converting it to
an untagged representation since those will deoptimize for the hole
value anyway.
Review URL: http://codereview.chromium.org/6964012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7827 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use a special slot for HContext, and fetch the value from there each time it is used. Allocate space for special slots in every HEnvironment. Fill them with constant undefined. Do not copy them to LEnvironment.
BUG=
TEST=
Review URL: http://codereview.chromium.org/6929066
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7807 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In my previous change I mixed up "compare" and "equals". This made us
miss the fast length check before comparing strings for equality.
Now we have a separate helper for "equals". It shares some of the
inner loop details with "compare". I'll see if this can be cleaned up
without making it unreadable.
Review URL: http://codereview.chromium.org/6928020
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7794 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The only difference to revision 7763 is the implementation in the
builtins file for arm and x64, plus a move of Array.prototype.toString
and Array.prototype.toLocaleString from should throw on null or
undefined to the non generic test cases in the function-call test (due
to us not currently supporting generic cases with these to functions)
Review URL: http://codereview.chromium.org/6928007
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7786 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This reduces the binary size by making the Is* type-test functions non-virtual.
I had to change Gap and Label instructions to have a common abstract superclass because both act as gap-instructions for the register allocator.
Review URL: http://codereview.chromium.org/6880204
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7691 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Rather than representing a use as a pointer to an HValue and then searching
for the specific (ambiguous) operand, we now represent a use as a pair of an
HValue and the input operand index. Additionally, use a linked list instead
of a growable array list since we never use random access.
This allows us to remove a bunch of similarly named and subtly different
functions from the HValue API. The cost in extra zone allocation per use is
partially offset by reusing use list nodes when replacing a use of one value
with another.
R=danno@chromium.org,fschneider@chromium.org
Review URL: http://codereview.chromium.org/6881044
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7674 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
For instructions that are marked as calls we can use:
1. Fixed input registers
2. Use-at-start policy (register, memory or constant).
(Memory or constant would not need the use-at-start policy, but
not specifying use-at-start prevents the allocator from using
a register even if there is one available. That's why use-at-start
is required and guarded by assertion)
Review URL: http://codereview.chromium.org/6853010
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7616 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- mutual inlining strict and non-strict functions in crankshaft.
- assignment to undefined variable with eval in scope.
- propagation of strict mode through lazy compilation.
BUG=
TEST=test/mjsunit/strict-mode.js test/mjsunit/strict-mode-opt.js
Review URL: http://codereview.chromium.org/6814012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7561 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Crankshaft is now the default on all platforms. This is the first
patch on the way to removing the classic code generator from the
system.
This time with no removal of the crankshaft flag. --nocrankshaft is
not at all the same as --always-full-compiler which I had used instead
for testing. That was what caused timeouts on the buildbots because of
repeated attempts to optimize hot functions. It makes sense to keep
the crankshaft flag in case you want to run only with the full
compiler and with no adaptive compilation.
R=vitalyr@chromium.org
Review URL: http://codereview.chromium.org/6759070
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7486 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In the cases where a global property cell cannot be used in the optimized code
use standard load ic to get the property instead of bailing out.
This is re-committing r7212 and r7215 which where reverted in r7239 with the addition of recoring the source position in the hydrogen code for the LoadGlobalCell instruction. To record that position an optional position field has been added to the variable proxy AST node.
Review URL: http://codereview.chromium.org/6758007
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7474 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix %NewObjectFromBound to correctly handle optimized frames (including those with inlined functions).
Fix %_IsConstructCall handling in hydrogen: when called from inlined function return false constant directly instead of emiting HIsConstructCall.
Fix success case in TraceInline.
BUG=v8:1229
TEST=test/mjsunit/regress/regress-1229.js
Review URL: http://codereview.chromium.org/6740023
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7472 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The previous implementation attempted to keep track of the needed
relocation size for deoptimization while generating the optimized
code. That was error prone. This patch moves the relocation resizing
to the deoptimizer as the last step of creating an optimized code
object.
The down side to this approach is that two relocation information byte
arrays are created for all optimized functions that do not have enough
relocation space for lazy deoptimization.
R=sgjesse@chromium.org
Review URL: http://codereview.chromium.org/6730050
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7360 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This change adds a new IR instruction for polymorphic loads. It performs
map compares and loads in one IR instruction instead of splitting each
load into a graph of map-compares and field loads.
The advantage is a smaller IR and less basic blocks, plus it allows to
do GVN on polymorphic loads.
Review URL: http://codereview.chromium.org/6708085
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7336 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This allows fast calls and inlining of functions like:
var o = {f: function() { return "foo"; }}
o.f();
Object literals that contain function literals are initially created a dictionary mode
object and only transformed to fast properties once all properties are computed and
added. This allows us to create constant function properties for functions declared
inside the object literal. Function literals inside object literals are marked for
pretenuring so that they work as contant function properties.
Object literals without functions should just function as before.
Review URL: http://codereview.chromium.org/6240012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7283 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
we know that both sides are Smi and those where we don't. Fix inlined
symbol table probes to cope with strings, undefined and null (indicating
a deleted entry). Some changes to other architectures that were found
with the new asserts.
Review URL: http://codereview.chromium.org/6682026
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7172 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Ensure that there is always enough bytes between consequtive calls in optimized code to write a call instruction at the return points without overlapping.
Add a call to deoptimize all functions after running tests with --stress-opt. This will catch some issues with functions which cannot be forcefully deoptimized. Some of the tests failed on ARM with that change without the rest of the changes in this change.
Review URL: http://codereview.chromium.org/6661022
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7132 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Worth mentioning:
- Specialized versions of pixel array and store/loads inside the generic stubs have been removed, since to have parity for all external arrays, 8 different versions would have to be inlined/checked.
- There's a new constant in v8.h for external arrays with pixel array elements.
Review URL: http://codereview.chromium.org/6546036
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7106 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Refactor construction of switch statements so it doesn't use class
HSubgraph.
There are also a few improvements. We do not use an auxiliary list of
comparisons because they're embedded as a linked list in the graph
under construction. We share a common break block for all breaks from
the same switch. We do not insert empty blocks unless necessary to
maintain edge-split form.
There is also a bug fix. The entry to a clause body is a potential
join and must have a join ID set, otherwise deoptimization within the
body can go to an unpredictable place in the unoptimized code.
Review URL: http://codereview.chromium.org/6650021
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7099 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Non-moveable code-stube are allocated in large object space. They are only required on ARM where the different C-entry stubs are required to never move.
This gets rid of pre-computing these stubs and hope that they never move. Also for crankshaft the C-entry stub which saved doubles is not generated in the snapshot so it ends up being generated at runtime and potentially move.
Review URL: http://codereview.chromium.org/6626072
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7097 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Ensure that there is always enough bytes between consequtive calls in
unoptimized code to write a call instruction at the return points
without overlapping.
This handles the case where two return points were only four bytes
apart (because the latter call was to a register).
BUG=v8:1234
Review URL: http://codereview.chromium.org/6624091
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7089 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Move strict mode flag from TemporaryScope to Scope so that it can be accessed from variable binding code.
Arguments do not alias in strict mode (ia32, x64 and arm, codegen and full codegen).
Hydrogen tolerates null arguments_shadow().
In codegen-<arch> arguments object is allocated eagerly to capture values before they get modified.
Review URL: http://codereview.chromium.org/6625048/
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7083 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Change the way we construct the graph for polymorphic loads to match that of
polymorphic stores.
Introduce a stack-allocated helper for saving and restoring all the
function-specific graph builder state that needs to change when we begin
translating an inlined function. Make this class authoritative by moving
redundant state out of the builder and deferring to the current function's
state.
Ensure that we always print a tracing message when abandoning an inlining
attempt.
Review URL: http://codereview.chromium.org/6628012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7074 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In built-in code we use arrays for internal computations.
This makes it possible to affect the built-in code by putting getters
or setters on the Array prototype chain.
This adds a new internal Array constructor that creates Arrays with
a very simplistic prototype chain that doesn't include any publicly
visible objects. These Arrays shoudl ofcourse never leak outside the
builtins, since that would expose the prototype object.
The prototype object contains only the array functions that we use:
push, pop and join (and not even a toString, so it doesn't stringify
well).
Also change uses of .call to %_CallFunction.
BUG=1206
Review URL: http://codereview.chromium.org/6602081
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7040 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This change makes the full code generator always materialize smi constants to match the behavior
of the environment tracked in the optimizing compiler. The mismatch between environment
and what the non-optimized code causes problems and potentially crashes when doing deoptimization
and OSR.
BUG=67732
Review URL: http://codereview.chromium.org/6592064
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6982 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use ToBooleanStub in DoTest instead of runtime call.
Try allocation in generated code in VisitRegExpLiteral.
Use TranscendentalCacheStub for sin, cos and log instead of calling runtime.
Minor "alignment" of the full codegen code across platforms.
Review URL: http://codereview.chromium.org/6597003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6953 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The old version only added extra space when we did indirect calls, but
the problem remains the same with normal calls that can be represented
as a single byte. When doing patching each call will always be at
least 2 bytes long because we use RUNTIME_ENTY as the reloc mode.
Review URL: http://codereview.chromium.org/6541053
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6894 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In revision 6795 I introduced an assertion in the deoptimizer that was
wrong. We check that curr_address - prev_address > patch_size(), but
prev_address is actually the address right after the last patched
call, so we just need to be larger than or equal to prev_address.
Review URL: http://codereview.chromium.org/6480068
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6797 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
