[Bug tree-optimization/21029] vrp miscompiles Ada front-end, drops loop exit test in well-defined wrap-around circumstances

[aoliva at gcc dot gnu dot org]

------- Additional Comments From aoliva at gcc dot gnu dot org  2005-04-14 
20:19 -------
Created an attachment (id=8632)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=8632&action=view)
C testcase that triggers the bug

The problem is that (from the vrp dump):

Simulating statement (from ssa_edges): jD.1487_6 = (intD.0) iD.1486_1;

Visiting statement:
jD.1487_6 = (intD.0) iD.1486_1;

(analyze_scalar_evolution
  (loop_nb = 1)
  (scalar = j_6)
(get_scalar_evolution
  (scalar = j_6)
  (scalar_evolution = {123, +, 1}_1))
(set_scalar_evolution
  (scalar = j_6)
  (scalar_evolution = {123, +, 1}_1))
)
Found new range [123, 2147483647] for j_6

[...]

Visiting statement:
if (jD.1487_6 < 0) goto <L2>; else goto <L1>;


Visiting conditional with predicate: j_6 < 0
With known ranges
        j_6: [123, 2147483647]

Predicate evaluates to: 0

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21029