[Bug tree-optimization/65752] Too strong optimizations int -> pointer casts

[gil.hur at sf dot snu.ac.kr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65752

--- Comment #33 from Chung-Kil Hur <gil.hur at sf dot snu.ac.kr> ---
Dear Richard,

Thanks for the detailed response.

I have a suggestion for a solution of the problem, which is based on my paper
to appear at PLDI 2015.

* A Formal C Memory Model Supporting Integer-Pointer Casts.
  Jeehoon Kang, Chung-Kil Hur, William Mansky, Dmitri Garbuzov, Steve
Zdancewic, Viktor Vafeiadis.
  http://sf.snu.ac.kr/gil.hur/publications/intptrcast.pdf

The suggestion is simple.
You do not need to turn off the phiopt optimizations.
We propose to slightly change the following assumption.

> PTA considers that all pointers coming from integer constants
> point to global memory only.

Here, if you change this as follows, you can solve the problem.

* All pointers coming from integer constants can point to only global memory
and
  local variables whose addresses have been cast to integers.

Also, we expect that this would not decrease the optimization performance of
GCC very much because those variables whose addresses have been cast to
integers tend to be escaped (e.g. passed to a hash function, or stored in the
memory).