[PATCH] Optimize UBSAN_NULL checks, add sanopt.c

[Yury Gribov]

On 11/05/2014 03:34 PM, Yury Gribov wrote:
> On 11/05/2014 03:21 PM, Jakub Jelinek wrote:
>> On Wed, Nov 05, 2014 at 03:16:49PM +0300, Yury Gribov wrote:
>>> On 11/05/2014 02:23 PM, Marek Polacek wrote:
>>>> On Wed, Nov 05, 2014 at 11:50:20AM +0100, Jakub Jelinek wrote:
>>>>> On Wed, Nov 05, 2014 at 11:29:19AM +0100, Marek Polacek wrote:
>>>>>> On Wed, Nov 05, 2014 at 12:54:37PM +0300, Yury Gribov wrote:
>>>>>>> Are you going to work on ASan soon?  I could rebase my patches on
>>>>>>> top of
>>>>>>> Marek's infrastructure.
>>>>>>
>>>>>> I'm not going to work on ASan today or tomorrow, but it'd be nice to
>>>>>> get this ASan opt in in this stage1.
>>>>>>
>>>>>> So if you can rebase your patch, I think that will be appreciated.
>>>>>
>>>>> Note, the algorithm we were discussing with Honza for the
>>>>> "is there any possibility of a freeing call on the path between a
>>>>> dominating
>>>>> and dominated ASAN_CHECK"
>>>>
>>>> Right.  Let me see then if I can implement the following soon, maybe
>>>> it makes sense to rebase Yuri's patch only on top of this algorithm.
>>>
>>> The algorithm looks like should_hoist_expr_to_dom in gcse.c btw.
>>>
>>> BTW have you considered relaxing the non-freeing restriction to not drop
>>> accesses to globals and stack variables? I wonder if we could win
>>> something
>>> there.
>>
>> Wouldn't it break most uses of __asan_poison_memory_region ?
>
> Most probably but I wonder if we should ask people to simply do asm
> volatile with memory clobber in this case?  And we probably shouldn't
> call the whole thing is_nonfreeing anyway.

Added Kostya to maybe comment on this.

-Y