[PING][PATCH] enable ranger and caching in pass_waccess

Martin Sebor msebor@gmail.com
Wed Aug 25 15:20:16 GMT 2021


Ping: Andrew, did I answer your questions?  Do you (or anyone else)
have any other comments on the latest patch below?

https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577865.html

On 8/20/21 4:16 PM, Martin Sebor wrote:
> On 8/20/21 7:09 AM, Andrew MacLeod wrote:
>> On 8/19/21 7:09 PM, Martin Sebor via Gcc-patches wrote:
>>> The attached patch changes the new access warning pass to use
>>> the per-function ranger instance.  To do that it makes a number
>>> of the global static functions members of the pass (that involved
>>> moving one to a later point in the file, increasing the diff;
>>> the body of the function hasn't changed otherwise).  Still more
>>> functions remain.  At the same time, the patch also enables
>>> the simple pointer_query cache to avoid repeatedly recomputing
>>> the properties of related pointers into the same objects, and
>>> makes the cache more effective (trunk fails to cache a bunch of
>>> intermediate results).  Finally, the patch enhances the debugging
>>> support for the cache.
>>>
>>> Other than the ranger/caching the changes have no user-visible
>>> effect.
>>
>>
>> Why are you calling enable/disable ranger if you are passing a ranger 
>> instance around instead of using the get_range_query (cfun)->range* 
>> calls?
> 
> The pass stores an instance of the pointer_query class which in
> turn stores a pointer to range_query (which is a copy of the ranger).
> So storing it also in pass_waccess isn't necessary and can be
> removed.  I've made that change in the attached update.  I'm not
> sure the corresponding pointer should at some point also be removed
> from the pointer_query class and replaced by calls to get_range_query
> (cfun).  If so, that would take some surgery to the strlen pass which
> also uses pointer_query and isn't quite ready to make this switch.
> 
> 
>>
>> Are you planning to transition to using the get_range_query() 
>> interface instead of keeping a range_query pointer in the 
>> pointer_query class?
> 
> This pass and to a smaller extent the pointer_query class that's
> used by it and the strlen pass are still a work in progress.
> I also still need to convert the strlen pass to use Ranger and
> I expect it will take some changes to pointer_query.  So at that
> point, if going through get_range_query (cfun) everywhere is what
> you recommend, I'm happy to do it.
> 
> Anyway, attached is an updated revision with the m_ranger member
> removed and a few helpers changed to take a range_query argument
> to use the pointer_query member instead.  It was retested on
> x86_64-linux.
> 
> Martin
> 
> PS There has been an effort to get rid of global variables from GCC,
> or, as the first step, to avoid accessing them directly(*).  If and
> when that happens, it seems like each pass will have to store either
> the ranger instance as a member (directly or indirectly, via a member
> of a class that stores it) or the function passed to pass::execute()
> if it wants to access either.
> 
> [*] https://gcc.gnu.org/pipermail/gcc-patches/2021-June/573975.html
> The patch at the link above wasn't approved but IIUC removing globals
> from GCC is still a goal.



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