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>

3 files changed, 4 insertions, 0 deletions

diff --git a/test/801-VoidCheckCast/classes.dex b/test/801-VoidCheckCast/classes.dex
new file mode 100644
index 0000000..e6f0f02
--- /dev/null
+++ b/test/801-VoidCheckCast/classes.dex
diff --git a/test/801-VoidCheckCast/expected.txt b/test/801-VoidCheckCast/expected.txt
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/test/801-VoidCheckCast/expected.txt
diff --git a/test/801-VoidCheckCast/info.txt b/test/801-VoidCheckCast/info.txt
new file mode 100644
index 0000000..422f740
--- /dev/null
+++ b/test/801-VoidCheckCast/info.txt
@@ -0,0 +1,4 @@
+A test that is only available as a DEX binary.
+
+This tests that an attempt to use check-cast with the void type doesn't
+cause the compiler to crash.