[Backport] 8267652: c2 loop unrolling by 8 results in reading memory …

…past array

Summary: Although 8267652 has already been ported in OpenJDK11,
OpenJDK11 has no vpternlog_mem() which exists in Dragonwell11. Hence
I have to introduce the missing fix of vpternlog_mem() in 8267652.

Test Plan: ci jtreg

src/hotspot/cpu/x86/x86.ad

@@ -8103,6 +8103,7 @@ instruct vpternlog(vec dst, vec src2, vec src3, immU8 func) %{
 %}
 
 instruct vpternlog_mem(vec dst, vec src2, memory src3, immU8 func) %{
+  predicate(vector_length_in_bytes(n->in(1)) > 8);
   match(Set dst (MacroLogicV (Binary dst src2) (Binary (LoadVector src3) func)));
   effect(TEMP dst);
   format %{ "vpternlogd $dst,$src2,$src3,$func\t! vector ternary logic" %}