From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Blue Swirl <blauwirbel@gmail.com>
Subject: Re: [Qemu-devel] Crash due to invalid env->current_tb
Date: Thu, 1 May 2008 17:04:43 +0100 [thread overview]
Message-ID: <200805011704.43953.paul@codesourcery.com> (raw)
In-Reply-To: <f43fc5580805010802o614fd763v354ff43892e98539@mail.gmail.com>
> > T0 = gen_func();
> >
> > For 64bit target T0 is 64bits so "=a" does not work and "=A" is needed.
> > The strange thing is that I need to throw away the upper 32bits because
> > otherwise it won't work. gen_func is defined to return just long but T0
> > is unsigned long long, this seems inconsistent. The 'and' does not
> > appear in 32bit targets so it does not harm there.
>
> This is because in this special case, T0 is not used as target CPU
> temporary, but instead to return next TB address. On i386 this is 32
> bits, so only EAX is needed. TCG does not touch EDX, so it contains
> garbage. This also means that moving EDX to high word of T0 and then
> throwing the high word away may be slightly wasteful.
Do we need to use T0 at all here? Can't we just use a normal local variable?
Paul
next prev parent reply other threads:[~2008-05-01 16:04 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-29 11:56 [Qemu-devel] Crash due to invalid env->current_tb Adam Lackorzynski
2008-04-29 17:09 ` Blue Swirl
2008-04-29 18:40 ` Adam Lackorzynski
2008-04-30 9:08 ` Alexander Graf
2008-04-30 15:11 ` Adam Lackorzynski
2008-04-30 15:21 ` Adam Lackorzynski
2008-04-30 17:09 ` Blue Swirl
2008-04-30 17:30 ` Alexander Graf
2008-04-30 18:21 ` Blue Swirl
2008-05-01 12:02 ` Adam Lackorzynski
2008-05-01 15:02 ` Blue Swirl
2008-05-01 16:04 ` Paul Brook [this message]
2008-05-01 16:15 ` Blue Swirl
2008-05-01 16:31 ` Paul Brook
2008-05-02 15:41 ` Adam Lackorzynski
2008-05-03 18:00 ` Blue Swirl
2008-05-03 22:02 ` Paul Brook
2008-04-30 15:28 ` Laurent Vivier
2008-04-30 20:36 ` Adam Lackorzynski
2008-05-02 1:39 ` Bernhard Kauer
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