From: Avi Kivity <avi@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH 5/8] tcg: Add interpreter for bytecode
Date: Sun, 18 Sep 2011 20:54:35 +0300 [thread overview]
Message-ID: <4E76305B.80108@redhat.com> (raw)
In-Reply-To: <4E759C43.5070708@redhat.com>
On 09/18/2011 10:22 AM, Paolo Bonzini wrote:
> On 09/18/2011 07:49 AM, Stefan Weil wrote:
>> Is there really any difference in the generated code?
>> gcc already uses a jump table internally to handle the
>> switch cases.
>
> You typically save something on range checks, and it enables a lot
> more tricks for use later (e.g. using multiple jump tables to perform
> simple peephole optimizations, or to divert code execution on
> interrupts).
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.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-09-18 17:54 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 [this message]
2011-09-19 6:52 ` Andi Kleen
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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