[Bug tree-optimization/64746] New: Loop with nested load/stores is not vectorized using aggressive if-conversion.

["ysrumyan at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64746

            Bug ID: 64746
           Summary: Loop with nested load/stores is not vectorized using
                    aggressive if-conversion.
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com

Attached simple test-case extracted from important suite is not vectorized even
if 'pragma omp simd' is used since ifcvt_repair_bool_pattern does not remove
all multiple uses and we get the following message:

test.c:11:14: note: bit-precision arithmetic not supported.
test.c:11:14: note: not vectorized: relevant stmt not supported: _ifc__90 =
x1_7 >= 0;

The problem is that statement splitting may introduce other multiple predicate
uses and iterative algorithm should be used.

I attached simple fix which cures the problem.