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

[Peter Maydell]

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().

-- PMM