RFR (XS): Temporarily disable ArrayCopyLoadStoreMaxElem with UseShenandoahMatrix

[Aleksey Shipilev]

This avoids compiler bug we know about, and let us do more extensive performance
experiments meanwhile:

diff -r a188e0e43a45 src/share/vm/runtime/arguments.cpp
--- a/src/share/vm/runtime/arguments.cpp	Fri Mar 10 15:29:45 2017 +0100
+++ b/src/share/vm/runtime/arguments.cpp	Fri Mar 10 15:39:26 2017 +0100
@@ -2098,6 +2098,11 @@
     FLAG_SET_DEFAULT(AlwaysPreTouch, false);
     FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
   }
+
+  if (UseShenandoahMatrix && FLAG_IS_DEFAULT(ArrayCopyLoadStoreMaxElem)) {
+    warning("UseShenandoahMatrix is enabled, setting
ArrayCopyLoadStoreMaxElem=0 to avoid compiler bug");
+    FLAG_SET_DEFAULT(ArrayCopyLoadStoreMaxElem, 0);
+  }
 }

 void Arguments::set_gc_specific_flags() {

Thanks,
-Aleksey