JavaMemoryModel: quick opcodes unsafe under weak memory models

From: Bill Pugh (
Date: Wed Jul 21 1999 - 14:19:53 EDT

After worrying about them for a while, I looked through the source
at the implementation of the quick opcodes in Sun's community source
VM (the quick opcodes are described in Chapter 9 of edition 1 of
the VM spec).

The implementation of the quick opcodes is very unsafe on any multiprocessor
system on which reads can be reordered. I'm not sure that
any safe implementation of quick opcodes is possible on a processor that
reorders reads.

How widely used is Sun's implementation of quick opcodes? Does the Dec JVM
use them?

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