[Bug tree-optimization/85315] missed range optimisation opportunity for derefences where index must be 0 or otherwise constrained

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85315

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |msebor at gcc dot gnu.org

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
A simpler test case that shows the same optimization opportunity is:

  int f (int i)
  {
    extern int x;
    int y;
    return &y + i == &x;
  }

A test case that both Clang and GCC get wrong is below.  (This will be
discussed at the next WG14 meeting -- see
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2222.htm#q23-can-one-do-comparison-between-pointers-to-objects-of-compatible-types-with-different-provenances-that-are-not-strictly-within-their-original-allocations)

  int g (int i)
  {
    int x, y, z;

    int *p = &x + i;
    int *q = &y;

    return p == q;
  }