In PhaseIdealLoop::do_unroll the assert
```
assert(trip_count > 0 && (julong)trip_count < (julong)max_juint/2, "sanity");
```
is too strict and should be `<=` instead of `<` (at least).

Reasoning:
with:
```
    int new_stride_con = stride_con * 2;
    int stride_m    = new_stride_con - (stride_con > 0 ? 1 : -1);
    jlong trip_count = (limit_con - init_con + stride_m)/new_stride_con;
```

if
limit_con = max_int = 2^31 - 1
init_con = min_int + 1 = -2^31 + 1
stride_con = 1
then
stride_m = 2
and trip_count = (2^31 - 1 - (-2^31 + 1) + 1)/2 = (2^32 - 1) / 2 = 2^31 - 1/2 = max_juint/2 + 1/2 (so = max_juint/2 in integer arithmetic)

This was observed on compiler/c2/Test6850611.java with -XX:+StressLoopPeeling

It is not clear to me if the case `init_con = min_int = -2^31` is possible, but I don't see why not. That would lead to trip_count = 2^31 = max_juint/2 + 1. In this case, a correct assert would be
```
assert(trip_count > 0 && (julong)trip_count <= (julong)max_juint/2 + 1, "sanity");
```