[Bug tree-optimization/37693] New: [alias-improvements-branch] can't prove non-zero number of iterations

[dorit at gcc dot gnu dot org]

This happens in testcase gfortran.dg/vect/pr32377.f90:
On the alias branch can't prove that number of iteratios is non zero:

Analyzing # of iterations of loop 1
  exit condition [2, + , 1](no_overflow) < D.1554_60
  bounds on difference of bases: -2147483650 ... 2147483645
  result:
    zero if D.1554_60 <= 1
    # of iterations (character(kind=4)) D.1554_60 + 0x0fffffffe, bounded by
2147483645
  (set_nb_iterations_in_loop = scev_not_known))
(get_loop_exit_condition
  if (D.1554_60 <= S.10_78)
)

pr32377.f90:9: note: not vectorized: number of iterations cannot be computed.
pr32377.f90:9: note: bad loop form.
pr32377.f90:4: note: vectorized 0 loops in function.

Using mainline we have:

Analyzing # of iterations of loop 1
  exit condition [2, + , 1](no_overflow) < D.1416_112
  bounds on difference of bases: 0 ... 2147483645
  result:
    # of iterations (character(kind=4)) D.1416_112 + 0x0fffffffe, bounded by
2147483645
  (set_nb_iterations_in_loop = (character(kind=4)) D.1416_112 + 0x0fffffffe))

pr32377.f90:9: note: ==> get_loop_niters:(character(kind=4)) D.1416_112 +
0x0ffffffff(get_loop_exit_condition
  if (S.10_78 >= D.1416_112)
)

pr32377.f90:9: note: Symbolic number of iterations is (character(kind=4))
D.1416_112 + 0x0ffffffff


-- 
           Summary: [alias-improvements-branch] can't prove non-zero number
                    of iterations
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dorit at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37693