RFR: 8286277: CDS VerifyError when calling clone() on object array

[Ioi Lam]

**Problem:**

When verifying an invokevirtual bytecode that calls a protected method in a superclass of the current class, the verifier requires that the object being invoked must be a subtype of the current class. This prevents invocation of protected methods in an unrelated class. For example, the following is disallowed -- the type `InvokeCloneInvalid` cannot invoke `clone()` on a `String`:


super public class InvokeCloneInvalid
    version 52:0
{
  public static Method test:"(Ljava/lang/String;)V"
    stack 1 locals 1
  {
    aload_0;
    invokevirtual Method "java/lang/Object".clone:"()Ljava/lang/Object;";
    return;
  }
}


However, there's a special case where invoking `Object.clone()` is allowed on all object arrays. Here's an example:


super public class InvokeCloneValid
    version 52:0
{
  public static Method test:"([Ljava/lang/Object;)V"
    stack 1 locals 1
  {
    aload_0;
    invokevirtual Method "java/lang/Object".clone:"()Ljava/lang/Object;";
    return;
  }


Before this PR. the Verifier would first do the assignability check. When a failure is encountered, the Verifier then checks for the special case and ignores the failure accordingly.

In the above case, the assignability check will fail because the object being invoked (an Object array) is not assignable to the current class (InvokeCloneValid)

The problem is that CDS remembers all the assignability checks and tries to replay them at runtime. Therefore, it will re-check the assignability of Object Array to InvokeCloneValid, and throw a VerifyError as a result.

**Proposed Fix**

In `ClassVerifier::verify_invoke_instructions()`, check the special case first, before doing the assignability check. This way, such invalid-but-ignored assignability checks are no longer performed and thus won't be remembered by CDS.

**Testing**

Tiers 1 - 4, plus 3 new test cases.

-------------

Commit messages:
 - fixed trailing spaces
 - 8286277: CDS VerifyError when calling clone() on object array

Changes: https://git.openjdk.java.net/jdk/pull/8737/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8737&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286277
  Stats: 348 lines in 7 files changed: 339 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8737.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8737/head:pull/8737

PR: https://git.openjdk.java.net/jdk/pull/8737