As a precondition for other compile speed improvements, I've been 
rewriting the way that GCC represents attributes.  The result is a 
medium-size patch that touches every language and many targets (a 
surprising number of targets don't define any special attributes at 
all).

The basic principle is that DECL_ATTRIBUTES and TREE_ATTRIBUTES now 
point to an attribute_list:

/* A structure representing 'attributes' on a DECL or TYPE node.
    Each attribute has a NAME (an IDENTIFIER_NODE) and possibly a VALUE. 
  */
struct one_attribute GTY(())
{
   tree name;
   tree value;
};

/* A counted list of attributes.  */
struct attribute_list_s GTY(())
{
   attribute_count n_attributes;
   /* There are 16 bits free here.  */
   struct one_attribute GTY((length ("%h.n_attributes"))) attribs[1];
};

This has many benefits, mostly flowing from the fact that it's not a 
TREE_LIST any more.

1. Do we think this would be acceptable for stage 3, or should I make a 
branch?
2. Would anyone be interested in helping me test it, especially on the 
more difficult architectures like alpha-vms or i386-netware?

diffstat on my current patch looks like:

  ada/gigi.h                 |    2
  ada/utils.c                |    2
  attribs.c                  |  347 
++++++++++++++++++++++++++-------------------
  builtin-attrs.def          |   62 +++-----
  c-common.c                 |  116 +++++++++------
  c-common.h                 |    4
  c-decl.c                   |   76 +++++----
  c-format.c                 |   25 +--
  c-objc-common.c            |    4
  c-parse.in                 |   98 ++++++------
  c-pragma.c                 |   10 -
  c-tree.h                   |   28 +--
  c-typeck.c                 |   12 -
  cgraphunit.c               |    2
  config/alpha/alpha.c       |    6
  config/arm/arm.c           |   37 ++--
  config/arm/pe.c            |   12 -
  config/avr/avr.c           |   14 -
  config/c4x/c4x.c           |    6
  config/frv/frv.c           |    2
  config/h8300/h8300.c       |   35 ----
  config/i386/i386.c         |   42 ++---
  config/i386/netware.c      |    8 -
  config/i386/winnt.c        |   22 +-
  config/ia64/ia64.c         |   10 -
  config/ip2k/ip2k.c         |    5
  config/m32r/m32r.c         |   10 -
  config/m68hc11/m68hc11.c   |   28 +--
  config/m68k/m68k.c         |    5
  config/mcore/mcore.c       |    6
  config/ns32k/ns32k.c       |    4
  config/rs6000/rs6000.c     |   22 +-
  config/sh/sh.c             |   10 -
  config/sh/symbian.c        |   28 +--
  config/sol2.c              |    8 -
  config/stormy16/stormy16.c |    6
  config/v850/v850.c         |   20 --
  coretypes.h                |    6
  cp/call.c                  |    2
  cp/class.c                 |    2
  cp/cp-tree.h               |   29 ++-
  cp/decl.c                  |   59 +++----
  cp/decl.h                  |    2
  cp/decl2.c                 |   14 -
  cp/friend.c                |    2
  cp/method.c                |    4
  cp/name-lookup.c           |   10 -
  cp/name-lookup.h           |    2
  cp/optimize.c              |    2
  cp/parser.c                |  176 ++++++++++++----------
  cp/pt.c                    |    2
  cp/tree.c                  |    4
  cp/typeck.c                |    8 -
  fold-const.c               |    4
  gengtype-lex.l             |    6
  integrate.c                |    9 -
  java/decl.c                |   46 ++---
  java/java-tree.h           |    2
  java/jcf-reader.c          |   12 -
  langhooks.c                |    4
  langhooks.h                |    2
  objc/objc-act.c            |   90 ++++++-----
  passes.c                   |    5
  print-tree.c               |   23 ++
  system.h                   |    2
  target-def.h               |    4
  target.h                   |   10 -
  targhooks.c                |   10 +
  targhooks.h                |    4
  tree-browser.c             |    9 -
  tree-inline.c              |    6
  tree.c                     |  307 
+++++++++++++++++++++++++--------------
  tree.h                     |   81 ++++++++--
  treelang/treetree.c        |    6
  varasm.c                   |    6
  75 files changed, 1171 insertions, 935 deletions