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Message from discussion Crankshaft Preemption Mechanism
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Vyacheslav Egorov  
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 More options Aug 31 2011, 3:53 pm
From: Vyacheslav Egorov <vego...@chromium.org>
Date: Wed, 31 Aug 2011 21:53:50 +0200
Local: Wed, Aug 31 2011 3:53 pm
Subject: Re: [v8-users] Crankshaft Preemption Mechanism
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Hi Kyle,

Optimizing compiler inserts stack checks (HStackCheck instruction)
explicitly at loop body's entry[1].

It also does an optimization pass[2] to remove redundant stack checks
that are dominated by function calls (as functions always does stack
check in the prologue).

Stack checks are important part of V8's interruption mechanism so both
compilers emit them to make all loops interruptable.

[1] http://code.google.com/p/v8/source/browse/trunk/src/hydrogen.cc#2823
[2] http://code.google.com/p/v8/source/browse/trunk/src/hydrogen.cc#1247

--
Vyacheslav Egorov

On Wed, Aug 31, 2011 at 9:27 PM, Kyle <kyle.n.mor...@gmail.com> wrote:
> Hello,

> Some time ago I noticed that the v8 compile was inserting stack limit
> checks at the back edges of loops.  I later found out that this check
> was doubling as a preemption mechanism to interrupt potentially long-
> running code.  However, I've noticed that the hydrogen/lithium
> compiler included with crankshaft does not seem to include these
> checks.  Is there a particular reason for this?  Is the previous
> design for JavaScript preemption no longer being pursued?

> --
> v8-users mailing list
> v8-users@googlegroups.com
> http://groups.google.com/group/v8-users


 
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