Shark: fix ldc(Class)

[Andrew Haley]

Gary Benson wrote:
> Andrew Haley wrote:
>> I've been trying to track down a mysterious bug in Shark for a
>> couple of weeks, and I finally got it.  It turns out that there's
>> no code generated for ldc(Class).  What fun!
>>
>> Oh well, I learned a lot...  :-)
> 
> Was it not hitting an Unimplemented() or similar?

It simply generated a read from the constant pool.  The cpool entry
points to a classOopDesc, so code has to be generated to get from the
classOopDesc to the Class.

Looking at sharkConstantPool.cpp, I now see java_mirror() which does the
same thing as the code I added.  I'll change my code to call that
function.

Incidentally, I think there has to me a memory barrier between reading
the tag and reading the constant pool entry.  The c++ interpeter
does this by calling byte_at_acquire().

Andrew.