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Optimize abort-to-prompt to avoid alloca

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* libguile/vm.c (capture_delimited_continuation): Adapt to caller not
  truncating vp->sp to vp->fp before calling.
  (abort_to_prompt): Inline vm_abort and avoid the alloca.
This commit is contained in:
Andy Wingo 2018-06-26 17:08:24 +02:00
parent 770360e066
commit bf66fdca55
1 changed files with 23 additions and 38 deletions
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61
libguile/vm.c
View file

@ -1329,8 +1329,10 @@ capture_delimited_continuation (struct scm_vm *vp,
scm_dynstack_relocate_prompts (dynstack, vp->stack_top - base_fp); scm_dynstack_relocate_prompts (dynstack, vp->stack_top - base_fp);
/* Capture from the base_fp to the top thunk application frame. */ /* Capture from the base_fp to the top thunk application frame. Don't
vm_cont = scm_i_vm_capture_stack (base_fp, vp->fp, vp->sp, vp->ip, dynstack, capture values from the most recent frame, as they are the abort
args. */
vm_cont = scm_i_vm_capture_stack (base_fp, vp->fp, vp->fp, vp->ip, dynstack,
flags); flags);
return scm_i_make_composable_continuation (vm_cont); return scm_i_make_composable_continuation (vm_cont);
@ -1345,18 +1347,21 @@ scm_i_vm_abort (SCM *tag_and_argv, size_t n)
} }
static void static void
vm_abort (struct scm_vm *vp, SCM tag, size_t n, SCM *argv, abort_to_prompt (scm_thread *thread, jmp_buf *current_registers)
jmp_buf *current_registers)
{ {
SCM cont; struct scm_vm *vp = &thread->vm;
scm_t_dynstack *dynstack = &SCM_I_CURRENT_THREAD->dynstack; scm_t_dynstack *dynstack = &thread->dynstack;
SCM tag, cont;
size_t nargs;
scm_t_bits *prompt; scm_t_bits *prompt;
scm_t_dynstack_prompt_flags flags; scm_t_dynstack_prompt_flags flags;
ptrdiff_t fp_offset, sp_offset; ptrdiff_t fp_offset, sp_offset;
union scm_vm_stack_element *fp, *sp; union scm_vm_stack_element *fp, *sp;
uint32_t *ip; uint32_t *ip;
jmp_buf *registers; jmp_buf *registers;
size_t i;
tag = SCM_FRAME_LOCAL (vp->fp, 1);
nargs = frame_locals_count (thread) - 2;
prompt = scm_dynstack_find_prompt (dynstack, tag, prompt = scm_dynstack_find_prompt (dynstack, tag,
&flags, &fp_offset, &sp_offset, &ip, &flags, &fp_offset, &sp_offset, &ip,
@ -1383,20 +1388,21 @@ vm_abort (struct scm_vm *vp, SCM tag, size_t n, SCM *argv,
/* Unwind. */ /* Unwind. */
scm_dynstack_unwind (dynstack, prompt); scm_dynstack_unwind (dynstack, prompt);
sp = sp - nargs - 1;
/* Shuffle abort arguments down to the prompt continuation. We have
to be jumping to an older part of the stack. */
if (sp < vp->sp)
abort ();
sp[nargs].as_scm = cont;
while (nargs--)
sp[nargs] = vp->sp[nargs];
/* Restore VM regs */ /* Restore VM regs */
vp->fp = fp; vp->fp = fp;
vp->sp = sp - n - 1; vp->sp = sp;
vp->ip = ip; vp->ip = ip;
/* Since we're jumping down, we should always have enough space. */
if (vp->sp < vp->stack_limit)
abort ();
/* Push vals */
vp->sp[n].as_scm = cont;
for (i = 0; i < n; i++)
vp->sp[n - i - 1].as_scm = argv[i];
/* Jump! */ /* Jump! */
longjmp (*registers, 1); longjmp (*registers, 1);
@ -1404,27 +1410,6 @@ vm_abort (struct scm_vm *vp, SCM tag, size_t n, SCM *argv,
abort (); abort ();
} }
static void
abort_to_prompt (scm_thread *thread, jmp_buf *current_registers)
{
struct scm_vm *vp = &thread->vm;
SCM tag;
size_t nargs, i;
SCM *argv;
tag = SCM_FRAME_LOCAL (vp->fp, 1);
nargs = frame_locals_count (thread) - 2;
/* FIXME: Avoid this alloca. */
argv = alloca (nargs * sizeof (SCM));
for (i = 0; i < nargs; i++)
argv[i] = vp->sp[nargs - i - 1].as_scm;
vp->sp = vp->fp;
vm_abort (vp, tag, nargs, argv, current_registers);
}
SCM SCM
scm_call_n (SCM proc, SCM *argv, size_t nargs) scm_call_n (SCM proc, SCM *argv, size_t nargs)
{ {