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Re: [Qemu-devel] [PATCH 0/3] tcg: Support debugging leakage of temporari

From: Aurelien Jarno
Subject: Re: [Qemu-devel] [PATCH 0/3] tcg: Support debugging leakage of temporaries
Date: Mon, 7 Mar 2011 09:42:04 +0100
User-agent: Mutt/1.5.20 (2009-06-14)

On Sun, Mar 06, 2011 at 09:52:56PM +0000, Peter Maydell wrote:
> On 6 March 2011 18:18, Aurelien Jarno <address@hidden> wrote:
> > On Wed, Feb 23, 2011 at 03:19:33PM +0000, Peter Maydell wrote:
> >> This patchset removes the ad-hoc debug code in target-arm for
> >> identifying cases where we leaked TCG temporary variables, in
> >> favour of an implementation in tcg itself.
> > I am basically fine with this patch series modulo the small comment you
> > made about patch 1.
> Thanks; I've sent a v2 which fixes that nit.
> > My only concern is that, given ARM code is quite
> > sensitive to this kind of issue (there is no real rule if the caller or
> > the callee should free the temp), that we forget to enable TCG debug to
> > validate a patch. On the other hand I fully agree that this kind of
> > check should not be done in "production" use.
> In the long term it would be good if we could make the ARM translate.c
> less brittle like this. Can we at least define a rule for where we're
> trying to get to so we can move in the right direction for new code?
> My suggestion would be that we should say that for gen_* functions
> the callee should always have to free temps passed in as arguments.
> This matches the convention for tcg_gen_$OP() and gen_helper_$WHATEVER().

I don't mind whatever convention, but my understanding is that this
doesn't match tcg_gen_$OP() and gen_helper_$WHATEVER(), which never free
temps passed in arguments.

Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net

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