[9] RFR(S): 8155608: String intrinsic range checks are not strict enough

[Tobias Hartmann]

Hi

please review the following patch:

https://bugs.openjdk.java.net/browse/JDK-8155608
http://cr.openjdk.java.net/~thartmann/8155608/jdk/webrev.00/
http://cr.openjdk.java.net/~thartmann/8155608/hotspot/webrev.00/

Some String API methods use StringUTF16.putChar/getChar to read a char value from a byte array. For performance reasons, putChar/getChar is intrinsified by C1/C2 without range checks (like the Unsafe counterparts). The Java callers are responsible for adding the corresponding explicit range checks if necessary.

I noticed that the Java level range checks in StringUTF16::compress(), StringUTF16::getChars() and StringLatin1::inflate() are not strong enough. Offset and length need to be multiplied by two because they index a char value in a byte array. I added a regression test that triggers the problem and also checks the other relevant intrinsics by invoking the methods with different arguments.

Tested with regression test (-Xint/-Xcomp) and RBT (running).

Thanks,
Tobias