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Subject: [Bug tree-optimization/55936] Missed VRP optimization
Date: Fri, 11 Jan 2013 10:48:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55936

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2013-01-11
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1
      Known to fail|                            |4.6.4, 4.7.2, 4.8.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-01-11 10:48:08 UTC ---
Confirmed.  We should see that i = baz () is not executed.

Visiting conditional with predicate: if (i_22 < 0)

With known ranges
        i_22: [j_12(D), j_12(D)]  EQUIVALENCES: { i_9(D) j_12(D) i_24 i_26 } (4
elements)

Predicate evaluates to: DON'T KNOW

that result happens because i_22 was computed as

Visiting statement:
i_22 = ASSERT_EXPR <i_24, i_24 == j_12(D)>;

Intersecting
  [j_12(D), j_12(D)]  EQUIVALENCES: { i_9(D) j_12(D) i_24 i_26 } (4 elements)
and
  [10, 30]  EQUIVALENCES: { i_9(D) i_26 } (2 elements)
to
  [j_12(D), j_12(D)]  EQUIVALENCES: { i_9(D) j_12(D) i_24 i_26 } (4 elements)
Found new range for i_22: [j_12(D), j_12(D)]

that's correct (equivalences have the [10, 30] range but they are not
checked during predicate evaluation it seems, we could also have
arbitrarily chosen [10, 30] instead of [j_12(D), j_12(D)] here)

This means we compute i as VARYING.