GCC not (optimally) exploiting restrict pointers?

[Mike Stump]

On Dec 15, 2004, at 4:34 AM, Richard Guenther wrote:
> Now, if I read 6.7.3 (7) correct, the second output is correct for the
> first case, too. And in fact, the Intel compiler produces the
> optimized output in _both_ cases.
Agreed.

> Is GCC right in not doing the optimization in the first case,
No.

> or has it just missed the optimization opportunity?
Just missed it.

I found http://www.lysator.liu.se/c/restrict.html an informative read...

I think:

  [#3] In what follows, a pointer expression E is said to be
  based on object P if (at some sequence point in the
  execution of B prior to the evaluation of E) modifying P to
  point to a copy of the array object into which it formerly
  pointed would change the value of E.106) Note that |
  ``based'' is defined only for expressions with pointer
  types.


is pretty clear as is 3.6 from the above link.