RFR(S): 8173147: [ctw] fails during compilation of sun.security.krb5.internal.crypto.RsaMd5DesCksumType::calculateKeyedChecksum with " graph should be schedulable"

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8173147/webrev.00/

When an ArrayCopy node is eliminated because its destination doesn't
escape and the destination is live at a safepoint, loads are generated
so the array content can be correctly initialized if it's reallocated
during deoptimization. If the safepoint is an uncommon trap, the loads
are pinned in the branch of the uncommon trap. The problem is that the
loads use the input memory of the arraycopy node as memory input but
there can be other nodes that modify memory between the ArrayCopy and
the uncommon trap. In some rare cases those nodes cause anti dependence
edges to be added and the graph becomes unschedulable. The fix consists
in setting the loads memory inputs to the memory of the safepoint
instead.

Roland.