8081823: C2 performs unsigned comparison against -1

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8081823/webrev.00/

C2 folds:

if (i <= a || i > b) {

as:

if (i - a - 1 >u b - a - 1) {

a == b is allowed and the test becomes then if (i-1 >u -1) { which is never true.

Same is true with if (i > b || i <= a) {

The fix folds it as:

if (i - a - 1 >=u b - a) {

which is always true for a == b

Roland.