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actually capture partial continuations

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* 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.
This commit is contained in:
Andy Wingo 2010-02-22 23:00:19 +01:00
parent 76e3816281
commit cee1d22c3c
5 changed files with 159 additions and 20 deletions
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119
libguile/control.c
View file

@ -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
scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv)
#ifdef WORDS_BIGENDIAN
#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...

3
libguile/control.h
View file

@ -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;

26
libguile/vm-i-system.c
View file

@ -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,
SCM_FRAME_DYNAMIC_LINK (fp),
SCM_FRAME_LOWER_ADDRESS (fp) - 1,
SCM_FRAME_RETURN_ADDRESS (fp),
SCM_FRAME_MV_RETURN_ADDRESS (fp));
vm_cont = scm_i_vm_capture_stack (vp->stack_base,
SCM_FRAME_DYNAMIC_LINK (fp),
SCM_FRAME_LOWER_ADDRESS (fp) - 1,
SCM_FRAME_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 ();
}

22
libguile/vm.c
View file

@ -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
vm_capture_continuation (SCM *stack_base,
SCM *fp, SCM *sp, scm_t_uint8 *ra, scm_t_uint8 *mvra)
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)
{
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 ();
}

9
libguile/vm.h
View file

@ -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);