TO-DO list
----------

  Virtual machine

    - Make _jc_env * have per-thread linkage:
      http://people.redhat.com/drepper/tls.pdf

    - Compress vtables by mapping overridden methods to superclass.
      Requires virtual method lookup at generation time.

    - Why does a conglomerated ELF object save a lot of memory?

    - Add a flag to control on-demand heap initialization. Perform GC
      attempts before heap is completely full. Implement jc.heap.initial.

    - Put the line number tables in a custom ELF section, then
      remove the section hack from _JC_STRING().

    - _jc_type contains pointer to bs->hint; use to inline allocations
      of small objects when the hint is correct and it's not the last
      block in the page. For large object, pointer always points to NULL.

    - Fix _JC_STACK_ALLOC() to detect stack overflows.

    - Handle the case where _JC_FULL_ALIGNMENT > sizeof(_jc_word). If so,
      then objects with an odd number of references could have primitive
      fields that are not aligned.

    - Use libunwind: http://www.hpl.hp.com/research/linux/libunwind/
      Should make the common case of uncaught exceptions faster.

    - http://www.cl.cam.ac.uk/Research/SRG/netos/lock-free/

    - Sun's SIGQUIT debugging menu:
	    http://docs.sun.com/db/doc/806-1367/6jalj6mv1?a=view

    - Show locked objects in SIGUSR1 output (by examining stack)

    - Fix all broken Mauve tests

    - Try jack benchmark; use gprof to find & optimize hotspots

    - Add support for retaining line numbers of inlined methods

    - Generational garbage collection: mark each heap pages as
      part of some generation. When a full page survives GC without
      losing any objects, bump it's generation.

  Code generation

    - Record inlined method information to fix disappearing stack frames.

    - Add lots of "restrict" keywords in the generated code.

    - Support enable/disable assertions; when disabled, use Soot
      to remove the assertion checking bytecode.

    - Find class initializers that just fill in static arrays with
      non-String constants and pre-generate them instead.

    - Make the dependency analysis more precise to avoid unecessary
      recompilations due to non-structural changes.

    - Implement thin-lock locking inline in the generated code.

  Other random ideas:

    - New gc/heap algorithm: single space, compacting, generational,
      compare-and-swap alloc. generational via starting point for compact.

Known bugs
----------

    - _jc_cs_fmod() is probably wrong on at least some platforms

    - Java 'volatile' longs and doubles should be accessed atomically.
      Need a new macro for reading&writing volatile longs & doubles.

    - Should impose global memory read barrier with MONITORENTER and global
      memory write barrier with MONITOREXIT in thin lock case. In the fat
      lock case, pthread_mutex_*() guarantees this for us.

Random Notes
------------

    - http://developer.java.sun.com/developer/bugParade/bugs/4329831.html
      What exactly is the memory model that we inherit from C? Are we
      violating the current JVM spec in any way?

    - Interesting Sun JVM bug:
      http://developer.java.sun.com/developer/bugParade/bugs/4699981.html

References
----------

    - New classfile format with CONSTANT_Class literals

	http://jcp.org/en/jsr/detail?id=202

    - Assertions

	http://java.sun.com/docs/books/jls/assert-spec.html#semantics
	http://java.sun.com/j2se/1.4/docs/guide/lang/assert.html

    - New Java memory model and JSR-133

	http://gee.cs.oswego.edu/dl/jmm/cookbook.html

    - JVM changes

	http://java.sun.com/docs/books/jls/jls-proposed-changes.html
	http://java.sun.com/docs/books/vmspec/2nd-edition/jvms-proposed-changes.html
	http://java.sun.com/docs/books/vmspec/2nd-edition/jvms-java5.html

    - GC

	http://www.cs.kent.ac.uk/people/staff/rej/gc.html
        http://java.sun.com/docs/hotspot/gc/

    - JNI 1.4

	http://java.sun.com/j2se/1.4.2/docs/guide/jni/jni-14.html
	http://java.sun.com/j2se/1.4.2/docs/guide/jni/spec/jniTOC.html

    - LLVM:

      http://llvm.cs.uiuc.edu/

    - MMTk:

      http://csdl.computer.org/comp/proceedings/icse/2004/2163/00/21630137abs.htm

$Id: NOTES,v 1.36 2005/07/03 19:34:18 archiecobbs Exp $