Re: [PATCH] Check DECL_CONTEXT of new/delete operators.

[Martin Liška]

On 4/3/20 5:26 PM, Jan Hubicka wrote:

On 3/31/20 2:29 PM, Jan Hubicka wrote:

Well, I basically went through all pointers and tried to get rid of as
many of them as possible.  CONTEXT pointers do increase size of SCCs
that increases chance they will not get merged and also processing time
of merging algorithm.  I guess if we need to stream more contexts we
could do that (and check the effect on merging and average SCC size)

Ok, do we want to stream contexts just for the new/delete operators?
Can you please prepare a streaming patch?

Hi,
I am still not convinced that context is useful here.
It took me a while to understand what the code does and why it fails,
but here is a testcase.
It fails for me with your patch and -O2 --param early-inlining-insns=100

The invalid transform is to remove pair
base:new and B:delete
B:new gets inlined and we get count out of sync.

Honza

#include <stdio.h>
volatile int idx;
struct base
{
   __attribute__((malloc,noinline))
   static void* operator new(unsigned long sz)
   {
     return ::operator new(sz);
   }

   __attribute__((malloc,noinline))
   static void operator delete(void* ptr)
   {
     --count[idx];
     ::operator delete(ptr);
   }
   volatile static int count[2];
};
volatile int base::count[2] = {0,0};
struct B:base
{
   static void* operator new(unsigned long sz)
   {
     ++count[idx];
     return base::operator new(sz);
   }

};


volatile int c=1;

int main(){
   for (int i; i<c;i++)
     {
       idx=0;
       delete new B;
       if (B::count[0] != 0)
        __builtin_abort ();
     }


   return 0;
}

May I please ping Jason, Nathan and Jonathan who can help us here?

Thanks,
Martin