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Partial continuations are RTL stubs

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* libguile/control.c: Implement partial continuations as RTL programs.

* libguile/programs.c (scm_i_rtl_program_minimum_arity): Add partial
  continuation case.

* libguile/vm-engine.c (compose-continuation): Fix to look for vm_cont
  from the free variables.

* libguile/vm-i-system.c (abort): Poison continuations captured in the
  stack VM, as the can't be rewound by the RTL stubs.
This commit is contained in:
Andy Wingo 2013-10-18 19:33:50 +02:00
parent d6fbf0c00e
commit d76de8716d
4 changed files with 24 additions and 70 deletions
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85
libguile/control.c
View file

@ -24,7 +24,7 @@
#include "libguile/_scm.h"
#include "libguile/control.h"
#include "libguile/objcodes.h"
#include "libguile/programs.h"
#include "libguile/instructions.h"
#include "libguile/vm.h"
@ -57,69 +57,25 @@ scm_i_prompt_pop_abort_args_x (SCM vm)
}
#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 OBJCODE_TAG SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0)
#if defined (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[]
#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) = { \
{ SCM_PACK (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)
#else
#define SCM_STATIC_OBJCODE(sym) \
static SCM sym; \
static scm_t_uint8 *sym##_bytecode; \
SCM_SNARF_INIT(sym##_bytecode = scm_gc_malloc_pointerless (sizeof(sym##_bytecode__unaligned), "partial continuation stub"); \
memcpy (sym##_bytecode, sym##_bytecode__unaligned, sizeof(sym##_bytecode__unaligned));) \
SCM_SNARF_INIT(sym = scm_double_cell (OBJCODE_TAG, \
(scm_t_bits)sym##_bytecode, \
SCM_UNPACK (SCM_BOOL_F), \
0);) \
static const scm_t_uint8 sym##_bytecode__unaligned[]
#endif
static const scm_t_uint32 compose_continuation_code[] =
{
SCM_PACK_RTL_24 (scm_rtl_op_compose_continuation, 0)
};
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_partial_cont_call, /* and go! */
/* 3 */ scm_op_nop,
/* 4 */ scm_op_nop, scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
/* 8 */
static SCM
make_partial_continuation (SCM vm_cont)
{
scm_t_bits nfree = 1;
scm_t_bits flags = SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION;
SCM ret;
/* 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, 3, /* arity: from ip 0 to ip 3 */
/* 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 */
};
ret = scm_words (scm_tc7_rtl_program | (nfree << 16) | flags, nfree + 2);
SCM_SET_CELL_WORD_1 (ret, compose_continuation_code);
SCM_RTL_PROGRAM_FREE_VARIABLE_SET (ret, 0, vm_cont);
return ret;
}
static SCM
reify_partial_continuation (SCM vm,
@ -128,7 +84,7 @@ reify_partial_continuation (SCM vm,
scm_t_dynstack *dynstack,
scm_i_jmp_buf *current_registers)
{
SCM vm_cont, ret;
SCM vm_cont;
scm_t_uint32 flags;
flags = SCM_F_VM_CONT_PARTIAL;
@ -155,12 +111,7 @@ reify_partial_continuation (SCM vm,
dynstack,
flags);
ret = scm_make_program (cont_objcode,
scm_c_make_vector (1, vm_cont),
SCM_BOOL_F);
SCM_SET_CELL_WORD_0 (ret,
SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
return ret;
return make_partial_continuation (vm_cont);
}
void

3
libguile/programs.c
View file

@ -527,7 +527,8 @@ scm_i_rtl_program_minimum_arity (SCM program, int *req, int *opt, int *rest)
if (SCM_PROGRAM_IS_FOREIGN (program))
return scm_i_foreign_arity (program, req, opt, rest);
if (SCM_PROGRAM_IS_CONTINUATION (program))
if (SCM_PROGRAM_IS_CONTINUATION (program)
|| SCM_PROGRAM_IS_PARTIAL_CONTINUATION (program))
{
*req = *opt = 0;
*rest = 1;

2
libguile/vm-engine.c
View file

@ -1273,7 +1273,7 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t nargs_)
scm_t_uint32 cont_idx;
SCM_UNPACK_RTL_24 (op, cont_idx);
vmcont = LOCAL_REF (cont_idx);
vmcont = SCM_RTL_PROGRAM_FREE_VARIABLE_REF (LOCAL_REF (0), cont_idx);
SYNC_IP ();
VM_ASSERT (SCM_VM_CONT_REWINDABLE_P (vmcont),

4
libguile/vm-i-system.c
View file

@ -1482,7 +1482,9 @@ VM_DEFINE_INSTRUCTION (89, abort, "abort", 1, -1, -1)
tail = sp[0];
stack_args = sp - n;
tag = sp[-(n + 1)];
vm_abort (vm, tag, n, stack_args, tail, sp - (n + 2), &registers);
/* Partial continuations are now RTL programs, and therefore not
resumable. Pass NULL as registers to indicate that fact. */
vm_abort (vm, tag, n, stack_args, tail, sp - (n + 2), NULL);
/* vm_abort should not return */
abort ();
}