From: Tom Tromey <tromey@redhat.com>
To: Helmut Eller <eller.helmut@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: indirect threading for bytecode interpreter
Date: Thu, 17 Sep 2009 15:06:46 -0600 [thread overview]
Message-ID: <m3ljkdi8m1.fsf@fleche.redhat.com> (raw)
In-Reply-To: <m2y6odjodc.fsf@gmail.com> (Helmut Eller's message of "Thu, 17 Sep 2009 22:41:03 +0200")
>>>>> "Helmut" == Helmut Eller <eller.helmut@gmail.com> writes:
Helmut> 5% doesn't sound like a lot to some people.
Shrug. Obviously I think the tradeoff is worth it, or I would not have
sent the patch. I don't think the result is all that ugly. And,
importantly, it is very low-hanging fruit.
Helmut> vmgen sounds like a good idea, but I fear that it makes the build
Helmut> process quite a bit more complicated.
You can check in the generated code.
vmgen is a nice idea. I rejected writing this as a direct-threaded
interpreter because I assumed that the added memory use would be a bad
tradeoff. But, if you are interested in that, perhaps I could take a
stab at it.
Helmut> I'm wondering why gcc can't perform this transformation from the
Helmut> switch based code. Is there no compiler setting to skip the
Helmut> range check in the switch statement?
It isn't about range checking but about eliminating a jump during the
dispatch.
GCC could be taught to do this. I imagine that it has always been
simpler for people to just update their interpreter than it has been to
try to fix GCC.
I don't think that some possible future GCC change should affect whether
this patch goes in.
Tom
next prev parent reply other threads:[~2009-09-17 21:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-17 16:46 indirect threading for bytecode interpreter Tom Tromey
2009-09-17 18:21 ` Stefan Monnier
2009-09-17 19:20 ` Helmut Eller
2009-09-17 19:38 ` Tom Tromey
2009-09-17 20:41 ` Helmut Eller
2009-09-17 21:06 ` Tom Tromey [this message]
2009-09-17 22:48 ` Helmut Eller
2009-09-18 0:59 ` Stefan Monnier
2009-09-18 2:59 ` Tom Tromey
2009-09-17 20:43 ` Stefan Monnier
2009-09-17 20:57 ` Tom Tromey
2009-09-18 19:15 ` Dan Nicolaescu
2009-09-18 20:26 ` Tom Tromey
2009-09-21 1:58 ` Dan Nicolaescu
2009-09-21 3:17 ` Tom Tromey
2009-09-21 13:13 ` Stefan Monnier
2009-09-21 13:21 ` David Kastrup
2009-09-21 13:47 ` joakim
2009-09-21 14:46 ` Stefan Monnier
2009-09-21 14:27 ` Tom Tromey
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