ART: Fix crash with unreachable void check-cast

return-void
check-cast v0, V
return-void

The above code sequence will not be rejected for the check-cast of a
void type because the check-cast is not reachable. However, when
GenerateSafeCastSet() is called from the compiler, this will cause
IsAssignableFrom(Conflict, Undefined) to be called, as it scans for all
check-casts across the code, regardless of its reachableness.

RegType::AssignableFrom() has been changed to handle a Conflict type,
whereas previously this would break the check that the lhs type is a
ReferenceType.

Additionally, GenerateSafeCastSet has been changed to never assess
instructions that weren't visited during verification.

Included is a new test DEX file, 801-VoidCheckCast, that uses this code
sequence.

Change-Id: I600055ab670ee48a075ffa867b46d2e74f5aa9c0
Signed-off-by: Stephen Kyle <stephen.kyle@arm.com>
diff --git a/test/etc/default-build b/test/etc/default-build
index ab859ec..6731ad3 100755
--- a/test/etc/default-build
+++ b/test/etc/default-build
@@ -17,6 +17,11 @@
 # Stop if something fails.
 set -e
 
+if [ -e classes.dex ]; then
+  zip $TEST_NAME.jar classes.dex
+  exit 0
+fi
+
 mkdir classes
 ${JAVAC} -d classes `find src -name '*.java'`