actually capture partial continuations

* libguile/control.c (cont_objcode): Along with a bunch of boilerplate
  that certainly needs to go in some central place, define this
  continuation-calling trampoline.
  (reify_partial_continuation): New function, returns a procedure that
  when called will reinstate a partial continuation.
  (scm_c_abort): Take an extra arg, the cookie. Actually reify a
  continuation.
  (scm_at_abort): Adapt to scm_c_abort change.

* libguile/control.h: Declare scm_c_abort change.

* libguile/vm-i-system.c (partial_cont_call): New instruction.
  (call/cc, tail-call/cc): Adapt to scm_i_vm_capture_stack change.
  (abort): Pass vm_cookie to abort.

* libguile/vm.h (SCM_F_VM_CONT_PARTIAL, SCM_F_VM_CONT_REWINDABLE): New
  flags.
  (struct scm_vm_cont): Add flags field.
  (SCM_VM_CONT_PARTIAL_P, SCM_VM_CONT_REWINDABLE_P): New predicates.

* libguile/vm.c (scm_i_vm_capture_stack): Rename from
  vm_capture_continuation, and make internal instead of static. Take a
  flags argument.
  (scm_i_vm_capture_continuation): Adapt to scm_i_vm_capture_stack
  change.
  (vm_abort): Plumb cookie to scm_c_abort.
  (vm_reinstate_partial_continuation): New stub.

libguile/control.c

@@ -22,6 +22,8 @@
 
 #include "libguile/_scm.h"
 #include "libguile/control.h"
+#include "libguile/objcodes.h"
+#include "libguile/instructions.h"
 #include "libguile/vm.h"
 
 
@@ -52,10 +54,115 @@ scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
   return ret;
 }
 
-SCM
+#ifdef WORDS_BIGENDIAN
-scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv)
+#define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
+#define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
+#else
+#define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
+#define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
+#endif
+
+#define ROUND_UP(len,align) (((len-1)|(align-1))+1)
+#define ALIGN_PTR(type,p,align) (type*)(ROUND_UP (((scm_t_bits)p), align))
+
+#ifdef SCM_ALIGNED
+#define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
+static const type sym[]
+#define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)\
+static SCM_ALIGNED (alignment) const type sym[]
+#else
+#define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
+static type *sym
+#define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)                  \
+SCM_SNARF_INIT(sym = scm_malloc (sizeof(sym##__unaligned) + alignment - 1); \
+               sym = ALIGN_PTR (type, sym, alignment);                  \
+               memcpy (sym, sym##__unaligned, sizeof(sym##__unaligned));) \
+static type *sym = NULL;                                                \
+static const type sym##__unaligned[]
+#endif
+
+#define STATIC_OBJCODE_TAG                                      \
+  SCM_PACK (scm_tc7_objcode | (SCM_F_OBJCODE_IS_STATIC << 8))
+
+#define SCM_STATIC_OBJCODE(sym)                                         \
+  SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
+  SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
+    { STATIC_OBJCODE_TAG, SCM_PACK (sym##__bytecode) },                 \
+    { SCM_BOOL_F, SCM_PACK (0) }                                        \
+  };                                                                    \
+  static const SCM sym = SCM_PACK (sym##__cells);                       \
+  SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
+
+  
+SCM_STATIC_OBJCODE (cont_objcode) = {
+  /* Like in continuations.c, but with partial-cont-call. */
+  OBJCODE_HEADER (8, 19),
+  /* leave args on the stack */
+  /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
+  /* 2 */ scm_op_object_ref, 1, /* push internal winds */
+  /* 4 */ scm_op_object_ref, 2, /* push external winds */
+  /* 6 */ scm_op_partial_cont_call, /* and go! */
+  /* 7 */ scm_op_nop, /* pad to 8 bytes */
+  /* 8 */
+
+  /* We could put some meta-info to say that this proc is a continuation. Not sure
+     how to do that, though. */
+  META_HEADER (19),
+  /* 0 */ scm_op_make_eol, /* bindings */
+  /* 1 */ scm_op_make_eol, /* sources */
+  /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 7, /* arity: from ip 0 to ip 7 */
+  /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
+  /* 7 */ scm_op_make_int8_0, /* 0 optionals */
+  /* 8 */ scm_op_make_true, /* and a rest arg */
+  /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
+  /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
+  /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
+  /* 18 */ scm_op_return /* and return */
+  /* 19 */
+};
+
+
+static SCM
+reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
+                            scm_t_int64 cookie)
 {
-  SCM winds, prompt = SCM_BOOL_F;
+  SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
+  scm_t_uint32 flags;
+
+  /* No need to reify if the continuation is never referenced in the handler. */
+  if (SCM_PROMPT_ESCAPE_P (prompt))
+    return SCM_BOOL_F;
+
+  dynwinds = scm_i_dynwinds ();
+  while (!scm_is_eq (dynwinds, extwinds))
+    {
+      intwinds = scm_cons (scm_car (dynwinds), intwinds);
+      dynwinds = scm_cdr (dynwinds);
+    }
+
+  flags = SCM_F_VM_CONT_PARTIAL;
+  if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
+    flags |= SCM_F_VM_CONT_REWINDABLE;
+
+  /* NULL RA and MVRA, as those get set when the cont is reinstated */
+  vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp,
+                                    SCM_VM_DATA (vm)->fp,
+                                    SCM_VM_DATA (vm)->sp,
+                                    NULL, NULL,
+                                    flags);
+
+  ret = scm_make_program (cont_objcode,
+                          scm_vector (scm_list_3 (vm_cont, intwinds, extwinds)),
+                          SCM_BOOL_F);
+  SCM_SET_CELL_WORD_0 (ret,
+                       SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_CONTINUATION);
+  return ret;
+}
+
+SCM
+scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
+{
+  SCM cont, winds, prompt = SCM_BOOL_F;
   long delta;
   size_t i;
 
@@ -83,6 +190,8 @@ scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv)
       abort ();
     }
 
+  cont = reify_partial_continuation (vm, prompt, winds, cookie);
+
   /* Unwind once more, beyond the prompt. */
   winds = SCM_CDR (winds), delta++;
   
@@ -99,7 +208,7 @@ scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv)
     abort ();
 
   /* Push vals */
-  *(++(SCM_VM_DATA (vm)->sp)) = SCM_BOOL_F; /* the continuation */
+  *(++(SCM_VM_DATA (vm)->sp)) = cont;
   for (i = 0; i < n; i++)
     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
@@ -123,7 +232,7 @@ SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
   for (i = 0; i < n; i++, args = scm_cdr (args))
     argv[i] = scm_car (args);
 
-  scm_c_abort (scm_the_vm (), tag, n, argv);
+  scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 
   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
      that's quite impossible, given that we're already in C-land here, so...

libguile/control.h

@@ -44,7 +44,8 @@ struct scm_prompt_registers
 
 SCM_INTERNAL SCM scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
                                     scm_t_int64 cookie);
-SCM_INTERNAL SCM scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv) SCM_NORETURN;
+SCM_INTERNAL SCM scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv,
+                              scm_t_int64 cookie) SCM_NORETURN;
 SCM_INTERNAL SCM scm_at_abort (SCM tag, SCM args) SCM_NORETURN;
 
 

libguile/vm-i-system.c

@@ -993,6 +993,17 @@ VM_DEFINE_INSTRUCTION (89, continuation_call, "continuation-call", 0, -1, 0)
   abort ();
 }
 
+VM_DEFINE_INSTRUCTION (94, partial_cont_call, "partial-cont-call", 0, -1, 0)
+{
+  SCM vmcont, intwinds, extwinds;
+  POP (extwinds);
+  POP (intwinds);
+  POP (vmcont);
+
+  vm_reinstate_partial_continuation (vm, vmcont, intwinds, extwinds);
+  NEXT;
+}
+
 VM_DEFINE_INSTRUCTION (59, tail_call_nargs, "tail-call/nargs", 0, 0, 1)
 {
   SCM x;
@@ -1099,7 +1110,7 @@ VM_DEFINE_INSTRUCTION (64, call_cc, "call/cc", 0, 1, 1)
   SCM proc, vm_cont, cont;
   POP (proc);
   SYNC_ALL ();
-  vm_cont = vm_capture_continuation (vp->stack_base, fp, sp, ip, NULL);
+  vm_cont = scm_i_vm_capture_stack (vp->stack_base, fp, sp, ip, NULL, 0);
   cont = scm_i_make_continuation (&first, vm, vm_cont);
   if (first) 
     {
@@ -1131,11 +1142,12 @@ VM_DEFINE_INSTRUCTION (65, tail_call_cc, "tail-call/cc", 0, 1, 1)
   SYNC_ALL ();
   /* In contrast to call/cc, tail-call/cc captures the continuation without the
      stack frame. */
-  vm_cont = vm_capture_continuation (vp->stack_base,
+  vm_cont = scm_i_vm_capture_stack (vp->stack_base,
-                                     SCM_FRAME_DYNAMIC_LINK (fp),
+                                    SCM_FRAME_DYNAMIC_LINK (fp),
-                                     SCM_FRAME_LOWER_ADDRESS (fp) - 1,
+                                    SCM_FRAME_LOWER_ADDRESS (fp) - 1,
-                                     SCM_FRAME_RETURN_ADDRESS (fp),
+                                    SCM_FRAME_RETURN_ADDRESS (fp),
-                                     SCM_FRAME_MV_RETURN_ADDRESS (fp));
+                                    SCM_FRAME_MV_RETURN_ADDRESS (fp),
+                                    0);
   cont = scm_i_make_continuation (&first, vm, vm_cont);
   if (first) 
     {
@@ -1511,7 +1523,7 @@ VM_DEFINE_INSTRUCTION (86, abort, "abort", 1, -1, -1)
   SYNC_REGISTER ();
   if (sp - n - 2 <= SCM_FRAME_UPPER_ADDRESS (fp))
     goto vm_error_stack_underflow;
-  vm_abort (vm, n);
+  vm_abort (vm, n, vm_cookie);
   /* vm_abort should not return */
   abort ();
 }

libguile/vm.c

@@ -91,9 +91,9 @@ scm_i_vm_cont_print (SCM x, SCM port, scm_print_state *pstate)
    continuation root is inside VM code, and call/cc was invoked within that same
    call to vm_run; but that's currently not implemented.
  */
-static SCM
+SCM
-vm_capture_continuation (SCM *stack_base,
+scm_i_vm_capture_stack (SCM *stack_base, SCM *fp, SCM *sp, scm_t_uint8 *ra,
-                         SCM *fp, SCM *sp, scm_t_uint8 *ra, scm_t_uint8 *mvra)
+                        scm_t_uint8 *mvra, scm_t_uint32 flags)
 {
   struct scm_vm_cont *p;
 
@@ -116,6 +116,7 @@ vm_capture_continuation (SCM *stack_base,
   p->fp = fp;
   memcpy (p->stack_base, stack_base, (sp + 1 - stack_base) * sizeof (SCM));
   p->reloc = p->stack_base - stack_base;
+  p->flags = flags;
   return scm_cell (scm_tc7_vm_cont, (scm_t_bits)p);
 }
 
@@ -178,7 +179,7 @@ SCM
 scm_i_vm_capture_continuation (SCM vm)
 {
   struct scm_vm *vp = SCM_VM_DATA (vm);
-  return vm_capture_continuation (vp->stack_base, vp->fp, vp->sp, vp->ip, NULL);
+  return scm_i_vm_capture_stack (vp->stack_base, vp->fp, vp->sp, vp->ip, NULL, 0);
 }
 
 static void
@@ -201,9 +202,9 @@ vm_dispatch_hook (SCM vm, int hook_num)
   vp->trace_level++;
 }
 
-static void vm_abort (SCM vm, size_t n) SCM_NORETURN;
+static void vm_abort (SCM vm, size_t n, scm_t_int64 cookie) SCM_NORETURN;
 static void
-vm_abort (SCM vm, size_t n)
+vm_abort (SCM vm, size_t n, scm_t_int64 vm_cookie)
 {
   size_t i;
   ssize_t tail_len;
@@ -224,7 +225,14 @@ vm_abort (SCM vm, size_t n)
   /* NULLSTACK (n + 1) */
   SCM_VM_DATA (vm)->sp -= n + 1;
 
-  scm_c_abort (vm, tag, n + tail_len, argv);
+  scm_c_abort (vm, tag, n + tail_len, argv, vm_cookie);
+}
+
+static void
+vm_reinstate_partial_continuation (SCM vm, SCM vm_cont, SCM intwinds,
+                                   SCM extwinds)
+{
+  abort ();
 }
 
 

libguile/vm.h

@@ -87,6 +87,9 @@ SCM_API SCM scm_set_vm_option_x (SCM vm, SCM key, SCM val);
 SCM_API SCM scm_vm_trace_level (SCM vm);
 SCM_API SCM scm_set_vm_trace_level_x (SCM vm, SCM level);
 
+#define SCM_F_VM_CONT_PARTIAL 0x1
+#define SCM_F_VM_CONT_REWINDABLE 0x2
+
 struct scm_vm_cont {
   SCM *sp;
   SCM *fp;
@@ -94,16 +97,22 @@ struct scm_vm_cont {
   scm_t_ptrdiff stack_size;
   SCM *stack_base;
   scm_t_ptrdiff reloc;
+  scm_t_uint32 flags;
 };
 
 #define SCM_VM_CONT_P(OBJ)	(SCM_NIMP (OBJ) && SCM_TYP7 (OBJ) == scm_tc7_vm_cont)
 #define SCM_VM_CONT_DATA(CONT)	((struct scm_vm_cont *) SCM_CELL_WORD_1 (CONT))
+#define SCM_VM_CONT_PARTIAL_P(CONT) (SCM_VM_CONT_DATA (CONT) & SCM_F_VM_CONT_PARTIAL)
+#define SCM_VM_CONT_REWINDABLE_P(CONT) (SCM_VM_CONT_DATA (CONT) & SCM_F_VM_CONT_REWINDABLE)
 
 SCM_API SCM scm_load_compiled_with_vm (SCM file);
 
 SCM_INTERNAL void scm_i_vm_print (SCM x, SCM port,
                                   scm_print_state *pstate);
 SCM_INTERNAL SCM scm_i_vm_capture_continuation (SCM vm);
+SCM_INTERNAL SCM scm_i_vm_capture_stack (SCM *stack_base, SCM *fp, SCM *sp,
+                                         scm_t_uint8 *ra, scm_t_uint8 *mvra,
+                                         scm_t_uint32 flags);
 SCM_INTERNAL void scm_i_vm_cont_print (SCM x, SCM port,
                                        scm_print_state *pstate);
 SCM_INTERNAL void scm_bootstrap_vm (void);