#include "programs.h"
\f
-/*
- * VM frames
- */
+/* Stack frames
+ ------------
-/*
- * It's a little confusing, but there are two representations of frames in this
- * file: frame pointers and Scheme objects wrapping those frame pointers. The
- * former uses the SCM_FRAME_... macro prefix, the latter SCM_VM_FRAME_..
- * prefix.
- *
- * The confusing thing is that only Scheme frame objects have functions that use
- * them, and they use the scm_frame_.. prefix. Hysterical raisins.
- */
+ It's a little confusing, but there are two representations of frames
+ in this file: frame pointers, and Scheme objects wrapping those frame
+ pointers. The former uses the SCM_FRAME macro prefix, the latter
+ SCM_VM_FRAME prefix.
+
+ The confusing thing is that only Scheme frame objects have functions
+ that use them, and they use the lower-case scm_frame prefix.
-/* VM Frame Layout
- ---------------
+ Stack frame layout
+ ------------------
+
+ /------------------\
+ | Local N-1 | <- sp
| ... |
- | Intermed. val. 0 | <- fp + nargs + nlocs
- +------------------+
- | Local variable 1 |
- | Local variable 0 | <- fp + nargs
- | Argument 1 |
- | Argument 0 | <- fp = SCM_FRAME_STACK_ADDRESS (fp)
- | Program | <- fp - 1
+ | Local 1 |
+ | Local 0 | <- fp = SCM_FRAME_LOCALS_ADDRESS (fp)
+==================+
- | Return address | <- SCM_FRAME_UPPER_ADDRESS (fp)
- | Dynamic link | <- fp - 3 = SCM_FRAME_DATA_ADDRESS (fp) = SCM_FRAME_LOWER_ADDRESS (fp)
+ | Return address |
+ | Dynamic link | <- fp - 2 = SCM_FRAME_LOWER_ADDRESS (fp)
+==================+
- | |
+ | | <- fp - 3 = SCM_FRAME_PREVIOUS_SP (fp)
- As can be inferred from this drawing, it is assumed that
- `sizeof (SCM *) == sizeof (SCM)', since pointers (the `link' parts) are
- assumed to be as long as SCM objects.
+ The calling convention is that a caller prepares a stack frame
+ consisting of the saved FP and the return address, followed by the
+ procedure and then the arguments to the call, in order. Thus in the
+ beginning of a call, the procedure being called is in slot 0, the
+ first argument is in slot 1, and the SP points to the last argument.
+ The number of arguments, including the procedure, is thus SP - FP +
+ 1.
- When a program returns multiple values, it will shuffle them down to
- start contiguously from slot 1, as for a tail call. This means that
- when the caller goes to access them, there are 2 or 3 empty words
- between the top of the caller stack and the bottom of the values,
- corresponding to the frame that was just popped.
-*/
+ After ensuring that the correct number of arguments have been passed,
+ a function will set the stack pointer to point to the last local
+ slot. This lets a function allocate the temporary space that it
+ needs once in the beginning of the call, instead of pushing and
+ popping the stack pointer during the call's extent.
+
+ When a program returns, it returns its values in the slots starting
+ from local 1, as if the values were arguments to a tail call. We
+ start from 1 instead of 0 for the convenience of the "values" builtin
+ function, which can just leave its arguments in place.
+
+ The callee resets the stack pointer to point to the last value. In
+ this way the caller knows how many values there are: it's the number
+ of words between the stack pointer and the slot at which the caller
+ placed the procedure.
+
+ After checking that the number of values returned is appropriate, the
+ caller shuffles the values around (if needed), and resets the stack
+ pointer back to its original value from before the call. */
+
+
+\f
/* This structure maps to the contents of a VM stack frame. It can
alias a frame directly. */
{
SCM *dynamic_link;
scm_t_uint8 *return_address;
- SCM program;
- SCM stack[1]; /* Variable-length */
+ SCM locals[1]; /* Variable-length */
};
+#define SCM_FRAME_LOWER_ADDRESS(fp) (((SCM *) (fp)) - 2)
#define SCM_FRAME_STRUCT(fp) \
- ((struct scm_vm_frame *) SCM_FRAME_DATA_ADDRESS (fp))
-
-#define SCM_FRAME_DATA_ADDRESS(fp) (((SCM *) (fp)) - 3)
-#define SCM_FRAME_STACK_ADDRESS(fp) (SCM_FRAME_STRUCT (fp)->stack)
-#define SCM_FRAME_UPPER_ADDRESS(fp) ((SCM*)&SCM_FRAME_STRUCT (fp)->return_address)
-#define SCM_FRAME_LOWER_ADDRESS(fp) ((SCM*)SCM_FRAME_STRUCT (fp))
+ ((struct scm_vm_frame *) SCM_FRAME_LOWER_ADDRESS (fp))
+#define SCM_FRAME_LOCALS_ADDRESS(fp) (SCM_FRAME_STRUCT (fp)->locals)
-#define SCM_FRAME_BYTE_CAST(x) ((scm_t_uint8 *) SCM_UNPACK (x))
-#define SCM_FRAME_STACK_CAST(x) ((SCM *) SCM_UNPACK (x))
+#define SCM_FRAME_PREVIOUS_SP(fp) (((SCM *) (fp)) - 3)
#define SCM_FRAME_RETURN_ADDRESS(fp) \
(SCM_FRAME_STRUCT (fp)->return_address)
(SCM_FRAME_STRUCT (fp)->dynamic_link)
#define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl) \
SCM_FRAME_DYNAMIC_LINK (fp) = (dl)
-#define SCM_FRAME_VARIABLE(fp,i) \
- (SCM_FRAME_STRUCT (fp)->stack[i])
-#define SCM_FRAME_PROGRAM(fp) \
- (SCM_FRAME_STRUCT (fp)->program)
+#define SCM_FRAME_LOCAL(fp,i) \
+ (SCM_FRAME_STRUCT (fp)->locals[i])
+
+#define SCM_FRAME_NUM_LOCALS(fp, sp) \
+ ((sp) + 1 - &SCM_FRAME_LOCAL (fp, 0))
+
+/* Currently (November 2013) we keep the procedure and arguments in
+ their slots for the duration of the procedure call, regardless of
+ whether the values are live or not. This allows for backtraces that
+ show the closure and arguments. We may allow the compiler to relax
+ this restriction in the future, if the user so desires. This would
+ conserve stack space and make GC more precise. We would need better
+ debugging information to do that, however.
+
+ Even now there is an exception to the rule that slot 0 holds the
+ procedure, which is in the case of tail calls. The compiler will
+ emit code that shuffles the new procedure and arguments into position
+ before performing the tail call, so there is a window in which
+ SCM_FRAME_PROGRAM does not correspond to the program being executed.
+
+ The moral of the story is to use the IP in a frame to determine what
+ procedure is being called. It is only appropriate to use
+ SCM_FRAME_PROGRAM in the prologue of a procedure call, when you know
+ it must be there. */
+
+#define SCM_FRAME_PROGRAM(fp) (SCM_FRAME_LOCAL (fp, 0))
\f
RUN_HOOK0 (SCM_VM_APPLY_HOOK)
#define PUSH_CONTINUATION_HOOK() \
RUN_HOOK0 (SCM_VM_PUSH_CONTINUATION_HOOK)
-#define POP_CONTINUATION_HOOK(vals, n) \
- RUN_HOOK (SCM_VM_POP_CONTINUATION_HOOK, vals, n)
+#define POP_CONTINUATION_HOOK(old_fp) \
+ RUN_HOOK (SCM_VM_POP_CONTINUATION_HOOK, \
+ &SCM_FRAME_LOCAL (old_fp, 1), \
+ SCM_FRAME_NUM_LOCALS (old_fp, vp->sp) - 1)
#define NEXT_HOOK() \
RUN_HOOK0 (SCM_VM_NEXT_HOOK)
-#define ABORT_CONTINUATION_HOOK(vals, n) \
- RUN_HOOK (SCM_VM_ABORT_CONTINUATION_HOOK, vals, n)
+#define ABORT_CONTINUATION_HOOK() \
+ RUN_HOOK (SCM_VM_ABORT_CONTINUATION_HOOK, \
+ LOCAL_ADDRESS (1), \
+ FRAME_LOCALS_COUNT () - 1)
#define RESTORE_CONTINUATION_HOOK() \
RUN_HOOK0 (SCM_VM_RESTORE_CONTINUATION_HOOK)
} while (0)
/* Reserve stack space for a frame. Will check that there is sufficient
- stack space for N locals, including the procedure, in addition to
- 2 words to set up the next frame. Invoke after preparing the new
- frame and setting the fp and ip. */
+ stack space for N locals, including the procedure. Invoke after
+ preparing the new frame and setting the fp and ip. */
#define ALLOC_FRAME(n) \
do { \
- SCM *new_sp = vp->sp = fp - 1 + n - 1; \
- CHECK_OVERFLOW (new_sp + 3); \
+ SCM *new_sp = vp->sp = LOCAL_ADDRESS (n - 1); \
+ CHECK_OVERFLOW (new_sp); \
} while (0)
/* Reset the current frame to hold N locals. Used when we know that no
stack expansion is needed. */
#define RESET_FRAME(n) \
do { \
- vp->sp = fp - 2 + n; \
+ vp->sp = LOCAL_ADDRESS (n - 1); \
} while (0)
-/* Compute the number of locals in the frame. This is equal to the
- number of actual arguments when a function is first called, plus
- one for the function. */
-#define FRAME_LOCALS_COUNT() \
- (vp->sp + 1 - (fp - 1))
+/* Compute the number of locals in the frame. At a call, this is equal
+ to the number of actual arguments when a function is first called,
+ plus one for the function. */
+#define FRAME_LOCALS_COUNT_FROM(slot) \
+ (vp->sp + 1 - LOCAL_ADDRESS (slot))
+#define FRAME_LOCALS_COUNT() \
+ FRAME_LOCALS_COUNT_FROM (0)
/* Restore registers after returning from a frame. */
#define RESTORE_FRAME() \
case opcode:
#endif
-#define LOCAL_REF(i) SCM_FRAME_VARIABLE ((fp - 1), i)
-#define LOCAL_SET(i,o) SCM_FRAME_VARIABLE ((fp - 1), i) = o
+#define LOCAL_ADDRESS(i) (&SCM_FRAME_LOCAL (fp, i))
+#define LOCAL_REF(i) SCM_FRAME_LOCAL (fp, i)
+#define LOCAL_SET(i,o) SCM_FRAME_LOCAL (fp, i) = o
#define VARIABLE_REF(v) SCM_VARIABLE_REF (v)
#define VARIABLE_SET(v,o) SCM_VARIABLE_SET (v, o)
#define RETURN_ONE_VALUE(ret) \
do { \
SCM val = ret; \
- SCM *sp = SCM_FRAME_LOWER_ADDRESS (fp); \
+ SCM *old_fp = fp; \
VM_HANDLE_INTERRUPTS; \
ip = SCM_FRAME_RTL_RETURN_ADDRESS (fp); \
fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp); \
/* Clear frame. */ \
- sp[0] = SCM_BOOL_F; \
- sp[1] = SCM_BOOL_F; \
+ old_fp[-1] = SCM_BOOL_F; \
+ old_fp[-2] = SCM_BOOL_F; \
/* Leave proc. */ \
- sp[3] = val; \
- vp->sp = sp + 3; \
- POP_CONTINUATION_HOOK (sp, 1); \
+ SCM_FRAME_LOCAL (old_fp, 1) = val; \
+ vp->sp = &SCM_FRAME_LOCAL (old_fp, 1); \
+ POP_CONTINUATION_HOOK (old_fp); \
NEXT (0); \
} while (0)
do { \
SCM vals = vals_; \
VM_HANDLE_INTERRUPTS; \
- fp[-1] = vm_builtin_apply; \
- fp[0] = vm_builtin_values; \
- fp[1] = vals; \
+ fp[0] = vm_builtin_apply; \
+ fp[1] = vm_builtin_values; \
+ fp[2] = vals; \
RESET_FRAME (3); \
ip = (scm_t_uint32 *) vm_builtin_apply_code; \
goto op_tail_apply; \
to pull all our state back from the ip/fp/sp.
*/
CACHE_REGISTER ();
- ABORT_CONTINUATION_HOOK (fp, FRAME_LOCALS_COUNT () - 1);
+ ABORT_CONTINUATION_HOOK ();
NEXT (0);
}
base[0] = SCM_PACK (fp); /* dynamic link */
base[1] = SCM_PACK (ip); /* ra */
base[2] = rtl_boot_continuation;
- fp = &base[3];
+ fp = &base[2];
ip = (scm_t_uint32 *) rtl_boot_continuation_code;
/* MV-call frame, function & arguments */
base[3] = SCM_PACK (fp); /* dynamic link */
base[4] = SCM_PACK (ip); /* ra */
base[5] = program;
- fp = vp->fp = &base[6];
+ fp = vp->fp = &base[5];
RESET_FRAME (nargs_ + 1);
}
if (SCM_STRUCTP (proc) && SCM_STRUCT_APPLICABLE_P (proc))
{
- fp[-1] = SCM_STRUCT_PROCEDURE (proc);
+ LOCAL_SET (0, SCM_STRUCT_PROCEDURE (proc));
continue;
}
if (SCM_HAS_TYP7 (proc, scm_tc7_smob) && SCM_SMOB_APPLICABLE_P (proc))
*/
VM_DEFINE_OP (0, halt, "halt", OP1 (U8_X24))
{
- scm_t_uint32 nvals = FRAME_LOCALS_COUNT() - 4;
- SCM ret;
-
/* Boot closure in r0, empty frame in r1/r2, proc in r3, values from r4. */
+ scm_t_uint32 nvals = FRAME_LOCALS_COUNT_FROM (4);
+ SCM ret;
+
if (nvals == 1)
ret = LOCAL_REF (4);
else
}
vp->ip = SCM_FRAME_RETURN_ADDRESS (fp);
- vp->sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
+ vp->sp = SCM_FRAME_PREVIOUS_SP (fp);
vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
return ret;
*/
VM_DEFINE_OP (7, return_values, "return-values", OP1 (U8_X24))
{
- scm_t_uint32 nvalues _GL_UNUSED = FRAME_LOCALS_COUNT();
- SCM *base = fp;
+ SCM *old_fp = fp;
VM_HANDLE_INTERRUPTS;
ip = SCM_FRAME_RTL_RETURN_ADDRESS (fp);
fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
/* Clear stack frame. */
- base[-2] = SCM_BOOL_F;
- base[-3] = SCM_BOOL_F;
+ old_fp[-1] = SCM_BOOL_F;
+ old_fp[-2] = SCM_BOOL_F;
- POP_CONTINUATION_HOOK (base, nvalues);
+ POP_CONTINUATION_HOOK (old_fp);
NEXT (0);
}
VM_HANDLE_INTERRUPTS;
SYNC_IP ();
- switch (FRAME_LOCALS_COUNT () - 1)
+ switch (FRAME_LOCALS_COUNT_FROM (1))
{
case 0:
ret = subr ();
break;
case 1:
- ret = subr (fp[0]);
+ ret = subr (fp[1]);
break;
case 2:
- ret = subr (fp[0], fp[1]);
+ ret = subr (fp[1], fp[2]);
break;
case 3:
- ret = subr (fp[0], fp[1], fp[2]);
+ ret = subr (fp[1], fp[2], fp[3]);
break;
case 4:
- ret = subr (fp[0], fp[1], fp[2], fp[3]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4]);
break;
case 5:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5]);
break;
case 6:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5], fp[6]);
break;
case 7:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7]);
break;
case 8:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8]);
break;
case 9:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8], fp[9]);
break;
case 10:
- ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8], fp[9]);
+ ret = subr (fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], fp[8], fp[9], fp[10]);
break;
default:
abort ();
VM_HANDLE_INTERRUPTS;
// FIXME: separate args
- ret = scm_i_foreign_call (scm_cons (cif, pointer), fp);
+ ret = scm_i_foreign_call (scm_cons (cif, pointer), LOCAL_ADDRESS (1));
// NULLSTACK_FOR_NONLOCAL_EXIT ();
scm_i_check_continuation (contregs);
vm_return_to_continuation (scm_i_contregs_vm (contregs),
scm_i_contregs_vm_cont (contregs),
- FRAME_LOCALS_COUNT () - 1, fp);
+ FRAME_LOCALS_COUNT_FROM (1),
+ LOCAL_ADDRESS (1));
scm_i_reinstate_continuation (contregs);
/* no NEXT */
SYNC_IP ();
VM_ASSERT (SCM_VM_CONT_REWINDABLE_P (vmcont),
vm_error_continuation_not_rewindable (vmcont));
- vm_reinstate_partial_continuation (vm, vmcont, FRAME_LOCALS_COUNT () - 1, fp,
+ vm_reinstate_partial_continuation (vm, vmcont, FRAME_LOCALS_COUNT_FROM (1),
+ LOCAL_ADDRESS (1),
¤t_thread->dynstack,
®isters);
CACHE_REGISTER ();
dynstack = scm_dynstack_capture_all (¤t_thread->dynstack);
vm_cont = scm_i_vm_capture_stack (vp->stack_base,
SCM_FRAME_DYNAMIC_LINK (fp),
- SCM_FRAME_LOWER_ADDRESS (fp) - 1,
+ SCM_FRAME_PREVIOUS_SP (fp),
SCM_FRAME_RETURN_ADDRESS (fp),
dynstack,
0);
else
{
CACHE_REGISTER ();
- ABORT_CONTINUATION_HOOK (fp, FRAME_LOCALS_COUNT () - 1);
+ ABORT_CONTINUATION_HOOK ();
NEXT (0);
}
}
it continues with the next instruction. */
ip++;
SYNC_IP ();
- vm_abort (vm, LOCAL_REF (1), nlocals - 2, &LOCAL_REF (2),
- SCM_EOL, &LOCAL_REF (0), ®isters);
+ vm_abort (vm, LOCAL_REF (1), nlocals - 2, LOCAL_ADDRESS (2),
+ SCM_EOL, LOCAL_ADDRESS (0), ®isters);
/* vm_abort should not return */
abort ();
var = scm_lookup (LOCAL_REF (sym));
if (ip[1] & 0x1)
VM_ASSERT (VARIABLE_BOUNDP (var),
- vm_error_unbound (fp[-1], LOCAL_REF (sym)));
+ vm_error_unbound (fp[0], LOCAL_REF (sym)));
LOCAL_SET (dst, var);
NEXT (2);
var = scm_module_lookup (mod, sym);
if (ip[4] & 0x1)
- VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+ VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[0], sym));
*var_loc = var;
}
var = scm_private_lookup (SCM_CDR (modname), sym);
if (ip[4] & 0x1)
- VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+ VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[0], sym));
*var_loc = var;
}
scm_dynstack_push_prompt (¤t_thread->dynstack, flags,
LOCAL_REF (tag),
fp,
- &LOCAL_REF (proc_slot),
+ LOCAL_ADDRESS (proc_slot),
(scm_t_uint8 *)(ip + offset),
®isters);
NEXT (3);
HCoop / bpt / guile.git / commitdiff