[Guile-commits] 18/26: Refactor continuation capture in VM

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit 51e35158bad42b8db28e9272ebb279f17b76dbe4
Author: Andy Wingo <address@hidden>
Date:   Tue Jun 26 11:25:07 2018 +0200

    Refactor continuation capture in VM
    
    * libguile/continuations.h:
    * libguile/continuations.c (scm_i_make_continuation): Refactor to expect
      registers to already be captured.
    * libguile/scm.h (scm_i_thread): Add forward decl.
    * libguile/threads.h (struct scm_i_thread): Just fill in the struct
      type.
    * libguile/vm-engine.c (call/cc); Use the registers already captured
      before entering the VM.
---
 libguile/continuations.c | 21 +++------------------
 libguile/continuations.h |  4 ++--
 libguile/scm.h           |  2 +-
 libguile/threads.h       |  4 ++--
 libguile/vm-engine.c     | 37 +++++++++++--------------------------
 5 files changed, 19 insertions(+), 49 deletions(-)

diff --git a/libguile/continuations.c b/libguile/continuations.c
index c99e0eb..172168e 100644
--- a/libguile/continuations.c
+++ b/libguile/continuations.c
@@ -166,18 +166,12 @@ restore_auxiliary_stack (scm_i_thread *thread, 
scm_t_contregs *continuation)
 #endif
 }
 
-/* this may return more than once: the first time with the escape
-   procedure, then subsequently with SCM_UNDEFINED (the vals already having 
been
-   placed on the VM stack). */
-#define FUNC_NAME "scm_i_make_continuation"
 SCM 
-scm_i_make_continuation (int *first, struct scm_vm *vp, SCM vm_cont)
+scm_i_make_continuation (jmp_buf *registers, scm_i_thread *thread, SCM vm_cont)
 {
-  scm_i_thread *thread = SCM_I_CURRENT_THREAD;
   SCM cont;
   scm_t_contregs *continuation;
   long stack_size;
-  const void *saved_cookie;
   SCM_STACKITEM * src;
 
   SCM_FLUSH_REGISTER_WINDOWS;
@@ -193,23 +187,14 @@ scm_i_make_continuation (int *first, struct scm_vm *vp, 
SCM vm_cont)
 #endif
   continuation->offset = continuation->stack - src;
   memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size);
+  memcpy (continuation->jmpbuf, registers, sizeof (*registers));
   continuation->vm_cont = vm_cont;
-  saved_cookie = vp->resumable_prompt_cookie;
   capture_auxiliary_stack (thread, continuation);
 
   SCM_NEWSMOB (cont, tc16_continuation, continuation);
 
-  *first = !setjmp (continuation->jmpbuf);
-  if (*first)
-    return make_continuation_trampoline (cont);
-  else
-    {
-      vp->resumable_prompt_cookie = saved_cookie;
-      scm_gc_after_nonlocal_exit ();
-      return SCM_UNDEFINED;
-    }
+  return make_continuation_trampoline (cont);
 }
-#undef FUNC_NAME
 
 int
 scm_i_continuation_to_frame (SCM continuation, struct scm_frame *frame)
diff --git a/libguile/continuations.h b/libguile/continuations.h
index 6b52f26..9e044c4 100644
--- a/libguile/continuations.h
+++ b/libguile/continuations.h
@@ -67,8 +67,8 @@ typedef struct
 
 
 
-SCM_INTERNAL SCM scm_i_make_continuation (int *first,
-                                          struct scm_vm *vp,
+SCM_INTERNAL SCM scm_i_make_continuation (jmp_buf *registers,
+                                          scm_i_thread *thread,
                                           SCM vm_cont);
 SCM_INTERNAL void scm_i_reinstate_continuation (SCM cont) SCM_NORETURN;
 
diff --git a/libguile/scm.h b/libguile/scm.h
index 9996ec4..99b20fc 100644
--- a/libguile/scm.h
+++ b/libguile/scm.h
@@ -827,7 +827,7 @@ typedef int32_t scm_t_wchar;
 struct scm_frame;
 struct scm_vm;
 union scm_vm_stack_element;
-
+typedef struct scm_i_thread scm_i_thread; /* FIXME: Rename.  */
 
 
 
diff --git a/libguile/threads.h b/libguile/threads.h
index 50d4ba1..9f0ccc5 100644
--- a/libguile/threads.h
+++ b/libguile/threads.h
@@ -48,7 +48,7 @@ SCM_API scm_t_bits scm_tc16_condvar;
 
 struct scm_thread_wake_data;
 
-typedef struct scm_i_thread {
+struct scm_i_thread {
   struct scm_i_thread *next_thread;
 
   SCM handle;
@@ -105,7 +105,7 @@ typedef struct scm_i_thread {
   struct scm_vm vm;
   SCM_STACKITEM *base;
   jmp_buf regs;
-} scm_i_thread;
+};
 
 #define SCM_I_IS_THREAD(x)    SCM_SMOB_PREDICATE (scm_tc16_thread, x)
 #define SCM_I_THREAD_DATA(x)  ((scm_i_thread *) SCM_SMOB_DATA (x))
diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 6f2e093..0fdbf00 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -758,7 +758,6 @@ VM_NAME (scm_i_thread *thread, jmp_buf *registers, int 
resume)
     {
       SCM vm_cont, cont;
       scm_t_dynstack *dynstack;
-      int first;
 
       SYNC_IP ();
       dynstack = scm_dynstack_capture_all (&thread->dynstack);
@@ -768,35 +767,21 @@ VM_NAME (scm_i_thread *thread, jmp_buf *registers, int 
resume)
                                         SCM_FRAME_RETURN_ADDRESS (VP->fp),
                                         dynstack,
                                         0);
-      /* FIXME: Seems silly to capture the registers here, when they are
-         already captured in the registers local, which here we are
-         copying out to the heap; and likewise, the setjmp(&registers)
-         code already has the non-local return handler.  But oh
-         well!  */
-      cont = scm_i_make_continuation (&first, VP, vm_cont);
-
-      if (first)
-        {
-          RESET_FRAME (2);
-
-          SP_SET (1, SP_REF (0));
-          SP_SET (0, cont);
+      cont = scm_i_make_continuation (registers, thread, vm_cont);
 
-          if (SCM_LIKELY (SCM_PROGRAM_P (SP_REF (1))))
-            ip = SCM_PROGRAM_CODE (SP_REF (1));
-          else
-            ip = (uint32_t *) vm_apply_non_program_code;
+      RESET_FRAME (2);
 
-          APPLY_HOOK ();
+      SP_SET (1, SP_REF (0));
+      SP_SET (0, cont);
 
-          NEXT (0);
-        }
+      if (SCM_LIKELY (SCM_PROGRAM_P (SP_REF (1))))
+        ip = SCM_PROGRAM_CODE (SP_REF (1));
       else
-        {
-          CACHE_REGISTER ();
-          ABORT_CONTINUATION_HOOK ();
-          NEXT (0);
-        }
+        ip = (uint32_t *) vm_apply_non_program_code;
+
+      APPLY_HOOK ();
+
+      NEXT (0);
     }
 
   /* abort _:24