Patch: Imported boehm-gc 5.0alpha6

[Bryce McKinlay]

I have imported gc 5.0alpha6 into libgcj. The new version obsoletes many
of our libgcj-local hacks (for example, it should now know to look at
data_start on linux systems). Rather than post the entire patch, I have
posted the remaining diffs against the stock gc distribution. The
changes in dyn_load.c are some minor typo fixes that I have sent back to
Hans.

Here's the list of changes from the gc's README file:

 - GC_malloc_explicitly_typed and friends sometimes failed to
   initialize first word.
 - Added allocation routines and support in the marker for mark
descriptors
   in a type structure referenced by the first word of an object.  This
was
   introduced to support gcj, but hopefully in a way that makes it
   generically useful.
 - Added GC_requested_heapsize, and inhibited collections in
nonincremental
   mode if the actual used heap size is less than what was explicitly
   requested.
 - The Solaris pthreads version of GC_pthread_create didn't handle a
NULL
   attribute pointer.  Solaris thread support used the wrong default
thread
   stack size.  (Thanks to Melissa O'Neill for the patch.)
 - Changed PUSH_CONTENTS macro to no longer modify first parameter.
   This usually doesn't matter, but it was certainly an accident waiting

   to happen ...
 - Added GC_register_finalizer_no_order and friends to gc.h.  They're
   needed by Java implementations.
 - Integrated a fix for a win32 deadlock resulting from clock() calling
   malloc.  (Thanks to Chris Dodd.)
 - Integrated Hiroshi Kawashima's port to Linux/MIPS.  This was designed

   for a handheld platform, and may or may not be sufficient for other
   machines.
 - Fixed a va_arg problem with the %c specifier in cordprnt.c.  It
appears
   that this was always broken, but recent versions of gcc are the first
to
   report the (statically detectable) bug.
 - Added an attempt at a more general solution to dlopen
races/deadlocks.
   GC_dlopen now temporarily disables collection.  Still not ideal, but
...
 - Added -DUSE_I686_PREFETCH, -DUSE_3DNOW_PREFETCH, and support for IA64

   prefetch instructions.  May improve performance measurably, but I'm
not
   sure the code will run correctly on processors that don't support the

   instruction.  Won't build except with very recent gcc.
 - Added caching for header lookups in the marker.  This seems to result

   in a barely measurable performance gain.  Added support for
interleaved
   lookups of two pointers, but unconfigured that since the performance
   gain is currently near zero, and it adds to code size.
 - Changed Linux DATA_START definition to check both data_start and
   __data_start, since nothing else seems to be portable.
 - Added -DUSE_LD_WRAP to optionally take advantage of the GNU ld
function
   wrapping mechanism.  Probably currently useful only on Linux.
 - Moved some variables for the scratch allocator into GC_arrays, on
   Martin Hirzel's suggestion.
 - Fixed a win32 threads bug that caused the collector to not look for
   interior pointers from one of the thread stacks without
   ALL_INTERIOR_POINTERS.  (Thanks to Jeff Sturm.)
 - Added Mingw32 support.  (Thanks again to Jeff Sturm for the patch.)
 - Changed the alpha port to use the generic register scanning code
instead
   of alpha_mach_dep.s.  Alpha_mach_dep.s doesn't look for pointers in
fp
   registers, but gcc sometimes spills pointers there.  (Thanks to
Manuel Serrano
   for helping me debug this by email.)  Changed the IA64 code to do
something
   similar for similar reasons.


2000-04-19  Bryce McKinlay  <bryce@albatross.co.nz>

        Imported version version 5.0alpha6.
        * acinclude.m4: Bump version to 5.0a6.
        * configure.in: Don't use alpha_mach_dep.s.
        * include/private/config.h, irix_threads.c gc_watcom.asm: Delete

        obsolete files.