Re: [Qemu-devel] [PATCH v2 0/3] tcg: Support debugging leakage of temporaries

[Aurelien Jarno <aurelien@aurel32.net>]

On Sun, Mar 06, 2011 at 09:39:52PM +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.
> 
> Generally any temporaries created by a target while it is
> translating an instruction should be freed by the end of that
> instruction; otherwise carefully crafted guest code could cause
> TCG to run out of temporaries and assert.
> 
> Putting the leak-debugging code into TCG proper (a) makes more
> sense as this isn't at all arm-specific (b) makes it more
> comprehensive, as it now covers temporaries created in all ways,
> not just via the new_tmp()/dead_tmp() wrapper functions
> (c) avoids annoying false positives where eg a TCG temp created
> with tcg_const_i32() was passed to dead_tmp().
> 
> The tracking only happens if qemu was configured with
> --enable-debug-tcg. It should be easy to add to other targets if
> desired; it's just a matter of calling tcg_clear_temp_count()
> and tcg_check_temp_count() in the appropriate places.
> 
> Changes since v1:
>  use "do { } while (0)" for the non-debug version of the
>  tcg_clear_temp_count() macro to avoid creating empty statements
> 
> Peter Maydell (3):
>   tcg: Add support for debugging leakage of temporaries
>   target-arm: Remove ad-hoc leak checking code
>   target-arm: Use TCG temporary leak debugging facilities
> 
>  target-arm/translate.c |  705 +++++++++++++++++++++++------------------------
>  tcg/tcg.c              |   32 +++
>  tcg/tcg.h              |   17 ++
>  3 files changed, 394 insertions(+), 360 deletions(-)
> 
> 
> 

Thanks, all applied.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net