libguile/frames.h

   1 /* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013, 2014 Free Software Foundation, Inc.
   2  * *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public License
   5  * as published by the Free Software Foundation; either version 3 of
   6  * the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301 USA
  17  */
  18
  19 #ifndef _SCM_FRAMES_H_
  20 #define _SCM_FRAMES_H_
  21
  22 #include <libguile.h>
  23 #include "programs.h"
  24
  25 \f
  26 /* Stack frames
  27    ------------
  28
  29    It's a little confusing, but there are two representations of frames
  30    in this file: frame pointers, and Scheme objects wrapping those frame
  31    pointers.  The former uses the SCM_FRAME macro prefix, the latter
  32    SCM_VM_FRAME prefix.
  33
  34    The confusing thing is that only Scheme frame objects have functions
  35    that use them, and they use the lower-case scm_frame prefix.
  36
  37
  38    Stack frame layout
  39    ------------------
  40
  41    /------------------\
  42    | Local N-1        | <- sp
  43    | ...              |
  44    | Local 1          |
  45    | Local 0          | <- fp = SCM_FRAME_LOCALS_ADDRESS (fp)
  46    +==================+
  47    | Return address   |
  48    | Dynamic link     | <- fp - 2 = SCM_FRAME_LOWER_ADDRESS (fp)
  49    +==================+
  50    |                  | <- fp - 3 = SCM_FRAME_PREVIOUS_SP (fp)
  51
  52    The calling convention is that a caller prepares a stack frame
  53    consisting of the saved FP and the return address, followed by the
  54    procedure and then the arguments to the call, in order.  Thus in the
  55    beginning of a call, the procedure being called is in slot 0, the
  56    first argument is in slot 1, and the SP points to the last argument.
  57    The number of arguments, including the procedure, is thus SP - FP +
  58    1.
  59
  60    After ensuring that the correct number of arguments have been passed,
  61    a function will set the stack pointer to point to the last local
  62    slot.  This lets a function allocate the temporary space that it
  63    needs once in the beginning of the call, instead of pushing and
  64    popping the stack pointer during the call's extent.
  65
  66    When a program returns, it returns its values in the slots starting
  67    from local 1, as if the values were arguments to a tail call.  We
  68    start from 1 instead of 0 for the convenience of the "values" builtin
  69    function, which can just leave its arguments in place.
  70
  71    The callee resets the stack pointer to point to the last value.  In
  72    this way the caller knows how many values there are: it's the number
  73    of words between the stack pointer and the slot at which the caller
  74    placed the procedure.
  75
  76    After checking that the number of values returned is appropriate, the
  77    caller shuffles the values around (if needed), and resets the stack
  78    pointer back to its original value from before the call.  */
  79
  80
  81 \f
  82
  83 /* This structure maps to the contents of a VM stack frame.  It can
  84    alias a frame directly.  */
  85 struct scm_vm_frame
  86 {
  87   SCM *dynamic_link;
  88   scm_t_uint32 *return_address;
  89   SCM locals[1]; /* Variable-length */
  90 };
  91
  92 #define SCM_FRAME_LOWER_ADDRESS(fp)     (((SCM *) (fp)) - 2)
  93 #define SCM_FRAME_STRUCT(fp)                            \
  94   ((struct scm_vm_frame *) SCM_FRAME_LOWER_ADDRESS (fp))
  95 #define SCM_FRAME_LOCALS_ADDRESS(fp)    (SCM_FRAME_STRUCT (fp)->locals)
  96
  97 #define SCM_FRAME_PREVIOUS_SP(fp)       (((SCM *) (fp)) - 3)
  98
  99 #define SCM_FRAME_RETURN_ADDRESS(fp)            \
 100   (SCM_FRAME_STRUCT (fp)->return_address)
 101 #define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra)    \
 102   SCM_FRAME_STRUCT (fp)->return_address = (ra)
 103 #define SCM_FRAME_DYNAMIC_LINK(fp)              \
 104   (SCM_FRAME_STRUCT (fp)->dynamic_link)
 105 #define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl)      \
 106   SCM_FRAME_DYNAMIC_LINK (fp) = (dl)
 107 #define SCM_FRAME_LOCAL(fp,i)                   \
 108   (SCM_FRAME_STRUCT (fp)->locals[i])
 109
 110 #define SCM_FRAME_NUM_LOCALS(fp, sp)            \
 111   ((sp) + 1 - &SCM_FRAME_LOCAL (fp, 0))
 112
 113 \f
 114 /*
 115  * Heap frames
 116  */
 117
 118 #ifdef BUILDING_LIBGUILE
 119
 120 struct scm_frame
 121 {
 122   void *stack_holder;
 123   scm_t_ptrdiff fp_offset;
 124   scm_t_ptrdiff sp_offset;
 125   scm_t_uint32 *ip;
 126 };
 127
 128 enum scm_vm_frame_kind
 129   {
 130     SCM_VM_FRAME_KIND_VM,
 131     SCM_VM_FRAME_KIND_CONT
 132   };
 133
 134 #define SCM_VM_FRAME_P(x)       (SCM_HAS_TYP7 (x, scm_tc7_frame))
 135 #define SCM_VM_FRAME_KIND(x)    ((enum scm_vm_frame_kind) (SCM_CELL_WORD_0 (x) >> 8))
 136 #define SCM_VM_FRAME_DATA(x)    ((struct scm_frame *)SCM_CELL_WORD_1 (x))
 137 #define SCM_VM_FRAME_STACK_HOLDER(f)    SCM_VM_FRAME_DATA (f)->stack_holder
 138 #define SCM_VM_FRAME_FP_OFFSET(f)       SCM_VM_FRAME_DATA (f)->fp_offset
 139 #define SCM_VM_FRAME_SP_OFFSET(f)       SCM_VM_FRAME_DATA (f)->sp_offset
 140 #define SCM_VM_FRAME_FP(f)      (SCM_VM_FRAME_FP_OFFSET (f) + scm_i_frame_stack_base (f))
 141 #define SCM_VM_FRAME_SP(f)      (SCM_VM_FRAME_SP_OFFSET (f) + scm_i_frame_stack_base (f))
 142 #define SCM_VM_FRAME_IP(f)      SCM_VM_FRAME_DATA (f)->ip
 143 #define SCM_VM_FRAME_OFFSET(f)  scm_i_frame_offset (f)
 144 #define SCM_VALIDATE_VM_FRAME(p,x)      SCM_MAKE_VALIDATE (p, x, VM_FRAME_P)
 145
 146 SCM_INTERNAL SCM* scm_i_frame_stack_base (SCM frame);
 147 SCM_INTERNAL scm_t_ptrdiff scm_i_frame_offset (SCM frame);
 148
 149 /* See notes in frames.c before using this.  */
 150 SCM_INTERNAL SCM scm_c_frame_closure (enum scm_vm_frame_kind kind,
 151                                       const struct scm_frame *frame);
 152
 153 SCM_INTERNAL SCM scm_c_make_frame (enum scm_vm_frame_kind kind,
 154                                    const struct scm_frame *frame);
 155
 156 SCM_INTERNAL int scm_c_frame_previous (enum scm_vm_frame_kind kind,
 157                                        struct scm_frame *frame);
 158
 159 #endif
 160
 161 SCM_API SCM scm_frame_p (SCM obj);
 162 SCM_API SCM scm_frame_procedure (SCM frame);
 163 SCM_API SCM scm_frame_call_representation (SCM frame);
 164 SCM_API SCM scm_frame_arguments (SCM frame);
 165 SCM_API SCM scm_frame_source (SCM frame);
 166 SCM_API SCM scm_frame_num_locals (SCM frame);
 167 SCM_API SCM scm_frame_local_ref (SCM frame, SCM index);
 168 SCM_API SCM scm_frame_local_set_x (SCM frame, SCM index, SCM val);
 169 SCM_API SCM scm_frame_address (SCM frame);
 170 SCM_API SCM scm_frame_stack_pointer (SCM frame);
 171 SCM_API SCM scm_frame_instruction_pointer (SCM frame);
 172 SCM_API SCM scm_frame_return_address (SCM frame);
 173 SCM_API SCM scm_frame_dynamic_link (SCM frame);
 174 SCM_API SCM scm_frame_previous (SCM frame);
 175
 176 SCM_INTERNAL void scm_i_frame_print (SCM frame, SCM port,
 177                                      scm_print_state *pstate);
 178 SCM_INTERNAL void scm_init_frames (void);
 179
 180 #endif /* _SCM_FRAMES_H_ */
 181
 182 /*
 183   Local Variables:
 184   c-file-style: "gnu"
 185   End:
 186 */