Fix MAKE-LOAD-FORM data-flow ordering in the file compiler

[blakemcbride]

Fix MAKE-LOAD-FORM data-flow ordering in the file compiler

Summary

• Fixes all 12 failing MAKE-LOAD-FORM.ORDER.* tests (ORDER.3–14) in
  the ANSI test suite: compiled-test failures drop from 64 to 52
  with no regressions.
• The file compiler now emits MAKE-LOAD-FORM creation and
  initialization forms to the fasl in data-flow dependency order,
  with init forms run ASAP per CLHS.
• Bumps *FASL-VERSION* from 43 to 44 (fasl layout changed).

Motivation

CLHS requires, for every literal instance handled by
MAKE-LOAD-FORM:

• the creation form runs after creation of every object it
  references (transitive closure);
• the init form runs after all objects it references are created,
  and as soon as its data-flow dependencies are satisfied.

Previously, ABCL emitted the creation + init forms inline at the
point where the instance was referenced, expanded via
get-instance-form as (let ((inst <creation>)) <init> inst). This
could not express cross-object dependencies and failed every
MAKE-LOAD-FORM.ORDER.* test that involved more than one instance
with dependencies between them.

Approach

Each fasl now carries a per-file instance vector
sys::*fasl-instances* indexed by integer. For every literal
instance referenced in the compile unit, the compiler emits (in
dependency order, before the top-level form that references it):

(setf (svref sys::*fasl-instances* N) <creation-form>)
<initialization-form>

and the original inline reference to the instance is rewritten to
#.(svref sys::*fasl-instances* N). The vector is allocated once in
the fasl prologue from the final instance count.

A two-phase dependency walker drives the emission:

1. %fasl-ensure-created(X) — recursively ensures creation of every
   instance embedded in X's creation form, then emits X's
   creation form. A re-entry while X is mid-creation is a real
   circular creation dependency and signals an error (CLHS: undefined
   behavior).
2. %fasl-ensure-initialized(X) — ensures X is created, then
   recursively ensures initialization of every instance embedded in
   X's init form, then emits X's init form. An in-progress init
   cycle is tolerated (CLHS leaves ordering within an init cycle
   unspecified).

To honor the ASAP rule (tests .6, .10–.12),
%fasl-ensure-created eagerly initializes X immediately after
emitting its creation form iff %fasl-init-deps-ready-p reports
that every object referenced by X's init form (ignoring X itself,
since MAKE-LOAD-FORM methods commonly embed ',x in their init
form) is already initialized. Otherwise init-X is emitted later,
either from the top-level walk that directly references X or from
another object's init-form walk.

Circularity detection

dump-instance now writes #.(svref sys::*fasl-instances* N)
instead of the legacy inline form. The existing *circularity*
walker (df-check-object) had to be taught to walk the same cons
that dump-instance ultimately writes, so a single reference cons
per instance is cached in *fasl-instance-refs* and reused by both
sites.

A new dynamic variable *fasl-emitting-to-fasl-stream* gates the new
behavior: when unbound (e.g. dumping constants into a class file via
SERIALIZE-OBJECT), dump-instance / df-check-instance fall back
to the legacy get-instance-form expansion.

Files changed

• src/org/armedbear/lisp/Load.java
  • Bump *FASL-VERSION* from 43 to 44.
  • Add the *FASL-INSTANCES* special; bindSpecial it per fasl in
    init_fasl.execute.
• src/org/armedbear/lisp/dump-form.lisp
  • Add per-fasl instance tables and the two-phase dep walk
    (%fasl-ensure-created, %fasl-ensure-initialized,
    %fasl-walk-for-deps, %fasl-init-deps-ready-p,
    %fasl-write-raw-form, %fasl-emit-toplevel-form).
  • Teach dump-instance and df-check-instance to use the cached
    ref cons when emitting to a fasl stream; retain the legacy
    get-instance-form path for non-fasl contexts.
• src/org/armedbear/lisp/compile-file.lisp
  • Bind the new instance-table specials in compile-from-stream.
  • Emit (setq sys::*fasl-instances* (make-array N)) in the fasl
    prologue when any instance was registered.
  • Route top-level forms through %fasl-emit-toplevel-form.

Test plan

• Smoke test mirroring MAKE-LOAD-FORM.ORDER.4 runs in the
  expected order:
  *ORDER* = (:CREATING B :CREATING A :INITIALIZING A :INITIALIZING B) (eql (ob-init-dep *b*) *a*) = T
• ant test.ansi.compiled: 64 → 52 failures / 21930 tests.
• All of MAKE-LOAD-FORM.ORDER.3 through .14 now pass.
• No new failures vs. baseline on this branch.

Compatibility

Fasl layout has changed (new prologue setq of
sys::*fasl-instances*, new per-reference (svref ...) form), hence
the *FASL-VERSION* bump. Older .abcl fasls are rejected by the
version check in Load.java and must be recompiled.

[blakemcbride]

Duplicated in pull request 743