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Date: Fri, 23 Sep 2011 10:14:11 +0800
From: =?utf-8?B?6Zmz6Z+L5Lu7?= <chenwj@iis.sinica.edu.tw>
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Subject: Re: [Qemu-devel] TB chaining
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To: Xin Tong <xerox.time.tech@gmail.com>
Cc: Lei Li <lilei@linux.vnet.ibm.com>, =?utf-8?B?6Zmz6Z+L5Lu7?= <chenwj@iis.sinica.edu.tw>, qemu-devel <qemu-devel@nongnu.org>

> if direct chaining is used, am I right to think that jmp_next and jmp_f=
irst
> will not be used ?

  You have to know that when we say "TB", it might means different
things according to the context.

  QEMU use struct TranslationBlock to record some information about
TB in the code cache. Take direct block chaining for example, when
I say we direct link tb1 to tb2, i.e., tb1 -> tb2, that actually
means two things. First, we patch the branch target of tb1 (in the
code cache) so that tb1 can jump to tb2 (in the code cache) and
executed. Meanwhile, we need to update tb1 (struct TranslationBlock)
and tb2 (struct TranslationBlock) to reflect the fact that tb1 (in the
code cache) is linked to tb2 (in the code cache). jmp_next and jmp_first
are fields of struct TranslationBlock, we use them when we need to
unchian TBs (in the code cache).

Regards,
chenwj

--=20
Wei-Ren Chen (=E9=99=B3=E9=9F=8B=E4=BB=BB)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667