Subrs are RTL programs

* libguile/gsubr.c: Define RTL stubs instead of stack VM stubs.
  (SUBR_STUB_CODE, get_subr_stub_code): Adapt to return a uint32_t*
  pointer instead of a SCM value.
  (create_subr): Create RTL procedures instead of stack VM procedures.
  For RTL procedures, the function pointer, name, and generic address
  pointer go inline to the procedure, as free variables.
  (scm_i_primitive_arity, scm_i_primitive_call_ip): New helpers.
  (scm_c_make_gsubr, scm_c_define_gsubr, scm_c_make_gsubr_with_generic)
  (scm_c_define_gsubr_with_generic): Adapt to create_gsubr being renamed
  to create_subr.

  Remove gsubr test code.

* libguile/gsubr.h (SCM_PRIMITIVE_P, SCM_PRIMITIVE_GENERIC_P): Only RTL
  programs can be primitives now.
  (SCM_SUBRF, SCM_SUBR_NAME, SCM_SUBR_GENERIC): These fields are now in
  the RTL free variables, not the object table.

* libguile/programs.c (scm_i_rtl_program_name):
  (scm_i_rtl_program_documentation):
  (scm_i_rtl_program_properties):
  (scm_i_rtl_program_minimum_arity): Implement these appropriately for
  primitives, which lack debugging information.
  (scm_primitive_p, scm_primitive_call_ip): New helpers.

* libguile/snarf.h: Remove static allocation for subrs.  Since there is
  nothing to allocate besides the program itself, which needs runtime
  relocation, static allocation is not a win.

* system/vm/program.scm: Fix up various arity-related things for
  primitives, which don't use ELF arity info.

* test-suite/tests/eval.test ("stack involving a primitive"): Add an
  XFAIL until we get just one VM.

module/system/vm/program.scm

@@ -198,7 +198,8 @@
 ;; returns list of list of bindings
 ;; (list-ref ret N) == bindings bound to the Nth local slot
 (define (program-bindings-by-index prog)
-  (cond ((program-bindings prog) => collapse-locals)
+  (cond ((rtl-program? prog) '())
+        ((program-bindings prog) => collapse-locals)
         (else '())))
 
 (define (program-bindings-for-ip prog ip)
@@ -291,14 +292,29 @@
 ;; the name "program-arguments" is taken by features.c...
 (define* (program-arguments-alist prog #:optional ip)
   "Returns the signature of the given procedure in the form of an association list."
-  (if (rtl-program? prog)
+  (cond
+   ((primitive? prog)
+    (match (procedure-minimum-arity prog)
+      (#f #f)
+      ((nreq nopt rest?)
+       (let ((start (primitive-call-ip prog)))
+         ;; Assume that there is only one IP for the call.
+         (and (or (not ip) (= start ip))
+              (arity->arguments-alist
+               prog
+               (list 0 0 nreq nopt rest? '(#f . ()))))))))
+   ((rtl-program? prog)
+    (let ((pc (and ip (+ (rtl-program-code prog) ip))))
       (or-map (lambda (arity)
-                (and #t
+                (and (or (not pc)
+                         (and (<= (arity-low-pc arity) pc)
+                              (< pc (arity-high-pc arity))))
                      (arity-arguments-alist arity)))
-              (or (find-program-arities (rtl-program-code prog)) '()))
-      (let ((arity (program-arity prog ip)))
-        (and arity
-             (arity->arguments-alist prog arity)))))
+              (or (find-program-arities (rtl-program-code prog)) '()))))
+   (else
+    (let ((arity (program-arity prog ip)))
+      (and arity
+           (arity->arguments-alist prog arity))))))
 
 (define* (program-lambda-list prog #:optional ip)
   "Returns the signature of the given procedure in the form of an argument list."
@@ -325,6 +341,14 @@
 
 (define (program-arguments-alists prog)
   (cond
+   ((primitive? prog)
+    (match (procedure-minimum-arity prog)
+      (#f '())
+      ((nreq nopt rest?)
+       (list
+        (arity->arguments-alist
+         prog
+         (list 0 0 nreq nopt rest? '(#f . ())))))))
    ((rtl-program? prog)
     (map arity-arguments-alist
          (or (find-program-arities (rtl-program-code prog)) '())))