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From: "Andi Kleen" <andi@firstfloor.org>
To: Avi Kivity <avi@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Andi Kleen <andi@firstfloor.org>,
	QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH 5/8] tcg: Add interpreter for bytecode
Date: Mon, 19 Sep 2011 08:52:05 +0200	[thread overview]
Message-ID: <51221ff5190e1823f0d6b602c4ca0f4d.squirrel@www.firstfloor.org> (raw)
In-Reply-To: <4E76305B.80108@redhat.com>


> I think it also improves branch target prediction - if you have a tight
> loop of a few opcodes the predictor can guess where you're headed (since
> there is a separate lookup key for each opcode), whereas with the
> original code, there's a single key which cannot be used to predict the
> branch target.

At least usually. I caught at least one version of gcc to CSE the jump
instruction into a common location in one of my interpreters
:-( But not all do it at least, and I hope gcc gets fixed.

It's still faster for other reasons usually.

-Andi

  reply	other threads:[~2011-09-19  6:52 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-17 19:59 [Qemu-devel] [PATCH 0/8] tcg/interpreter: Add TCG + interpreter for bytecode (virtual machine) Stefan Weil
2011-09-17 20:00 ` [Qemu-devel] [PATCH 1/8] tcg: Declare TCG_TARGET_REG_BITS in tcg.h Stefan Weil
2011-09-17 20:00 ` [Qemu-devel] [PATCH 2/8] tcg: Don't declare TCG_TARGET_REG_BITS in tcg-target.h Stefan Weil
2011-09-17 20:00 ` [Qemu-devel] [PATCH 3/8] tcg: Add forward declarations for local functions Stefan Weil
2011-09-17 21:40   ` Peter Maydell
2011-09-17 20:00 ` [Qemu-devel] [PATCH 4/8] tcg: Add some assertions Stefan Weil
2011-09-17 20:00 ` [Qemu-devel] [PATCH 5/8] tcg: Add interpreter for bytecode Stefan Weil
2011-09-18  4:03   ` Andi Kleen
2011-09-18  5:49     ` Stefan Weil
2011-09-18  7:22       ` Paolo Bonzini
2011-09-18 17:54         ` Avi Kivity
2011-09-19  6:52           ` Andi Kleen [this message]
2011-09-19 11:56             ` Avi Kivity
2011-09-19 14:48               ` Andi Kleen
2011-09-18 10:18   ` Blue Swirl
2011-09-19 16:43   ` Richard Henderson
2011-09-19 20:24   ` Stuart Brady
2011-10-16 21:54     ` Stuart Brady
2011-09-17 20:00 ` [Qemu-devel] [PATCH 6/8] tcg: Add bytecode generator for tcg interpreter Stefan Weil
2011-09-18 10:03   ` Blue Swirl
2011-09-19 22:28     ` Stuart Brady
2011-10-01 16:54   ` Andreas Färber
2011-10-01 21:25     ` Stefan Weil
2011-10-09 16:19       ` Andreas Färber
2011-09-17 20:00 ` [Qemu-devel] [PATCH 7/8] tcg: Add tcg interpreter to configure / make Stefan Weil
2011-09-18  9:37   ` Blue Swirl
2011-09-18 10:14     ` Stefan Weil
2011-09-17 20:00 ` [Qemu-devel] [PATCH 8/8] ppc: Support tcg interpreter on ppc hosts Stefan Weil
2011-09-17 21:31   ` Peter Maydell
2011-09-17 21:33     ` Stefan Weil
2011-09-18 10:26 ` [Qemu-devel] [PATCH 0/8] tcg/interpreter: Add TCG + interpreter for bytecode (virtual machine) Blue Swirl
2011-09-18 10:49   ` malc
2011-09-18 12:12     ` Blue Swirl
2011-09-18 12:46       ` malc
2011-09-18 13:00         ` Blue Swirl
2011-09-18 13:13           ` malc
2011-09-18 13:26             ` Blue Swirl
2011-09-25 20:37           ` Stefan Weil
2011-10-01 12:02             ` Blue Swirl
2011-09-18 15:02 ` Mulyadi Santosa
2011-09-18 15:13   ` Stefan Weil
2011-09-18 16:39     ` Mulyadi Santosa
2011-09-18 20:15       ` Stefan Weil
2011-09-19 15:14         ` Mulyadi Santosa
2011-09-19  8:40     ` David Gilbert
2011-09-19 10:20       ` Stefan Hajnoczi
2011-09-19 10:27         ` David Gilbert
2011-09-18 18:02 ` Avi Kivity

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