gdb/am29k-tdep.c

   1 /* Target-machine dependent code for the AMD 29000
   2    Copyright (C) 1990 Free Software Foundation, Inc.
   3    Contributed by Cygnus Support.  Written by Jim Kingdon.
   4
   5 This file is part of GDB.
   6
   7 This program is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 1, or (at your option)
  10 any later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21 #include "defs.h"
  22 #include "gdbcore.h"
  23 #include <stdio.h>
  24 #include "frame.h"
  25 #include "value.h"
  26 #include "param.h"
  27 #include "symtab.h"
  28 #include "inferior.h"
  29
  30 /* Structure to hold cached info about function prologues.  */
  31 struct prologue_info
  32 {
  33   CORE_ADDR pc;                 /* First addr after fn prologue */
  34   unsigned rsize, msize;        /* register stack frame size, mem stack ditto */
  35   unsigned mfp_used : 1;        /* memory frame pointer used */
  36   unsigned rsize_valid : 1;     /* Validity bits for the above */
  37   unsigned msize_valid : 1;
  38   unsigned mfp_valid : 1;
  39 };
  40
  41 /* Examine the prologue of a function which starts at PC.  Return
  42    the first addess past the prologue.  If MSIZE is non-NULL, then
  43    set *MSIZE to the memory stack frame size.  If RSIZE is non-NULL,
  44    then set *RSIZE to the register stack frame size (not including
  45    incoming arguments and the return address & frame pointer stored
  46    with them).  If no prologue is found, *RSIZE is set to zero.
  47    If no prologue is found, or a prologue which doesn't involve
  48    allocating a memory stack frame, then set *MSIZE to zero.
  49
  50    Note that both msize and rsize are in bytes.  This is not consistent
  51    with the _User's Manual_ with respect to rsize, but it is much more
  52    convenient.
  53
  54    If MFP_USED is non-NULL, *MFP_USED is set to nonzero if a memory
  55    frame pointer is being used.  */
  56 CORE_ADDR
  57 examine_prologue (pc, rsize, msize, mfp_used)
  58      CORE_ADDR pc;
  59      unsigned *msize;
  60      unsigned *rsize;
  61      int *mfp_used;
  62 {
  63   long insn;
  64   CORE_ADDR p = pc;
  65   int misc_index = find_pc_misc_function (pc);
  66   struct prologue_info *mi = 0;
  67
  68   if (misc_index >= 0)
  69     mi = (struct prologue_info *)misc_function_vector[misc_index].misc_info;
  70
  71   if (mi != 0)
  72     {
  73       int valid = 1;
  74       if (rsize != NULL)
  75         {
  76           *rsize = mi->rsize;
  77           valid &= mi->rsize_valid;
  78         }
  79       if (msize != NULL)
  80         {
  81           *msize = mi->msize;
  82           valid &= mi->msize_valid;
  83         }
  84       if (mfp_used != NULL)
  85         {
  86           *mfp_used = mi->mfp_used;
  87           valid &= mi->mfp_valid;
  88         }
  89       if (valid)
  90         return mi->pc;
  91     }
  92
  93   if (rsize != NULL)
  94     *rsize = 0;
  95   if (msize != NULL)
  96     *msize = 0;
  97   if (mfp_used != NULL)
  98     *mfp_used = 0;
  99
 100   /* Prologue must start with subtracting a constant from gr1.
 101      Normally this is sub gr1,gr1,<rsize * 4>.  */
 102   insn = read_memory_integer (p, 4);
 103   if ((insn & 0xffffff00) != 0x25010100)
 104     {
 105       /* If the frame is large, instead of a single instruction it
 106          might be a pair of instructions:
 107          const <reg>, <rsize * 4>
 108          sub gr1,gr1,<reg>
 109          */
 110       int reg;
 111       /* Possible value for rsize.  */
 112       unsigned int rsize0;
 113
 114       if ((insn & 0xff000000) != 0x03000000)
 115         {
 116           p = pc;
 117           goto done;
 118         }
 119       reg = (insn >> 8) & 0xff;
 120       rsize0 = (((insn >> 8) & 0xff00) | (insn & 0xff));
 121       p += 4;
 122       insn = read_memory_integer (p, 4);
 123       if ((insn & 0xffffff00) != 0x24010100
 124           || (insn & 0xff) != reg)
 125         {
 126           p = pc;
 127           goto done;
 128         }
 129       if (rsize != NULL)
 130         *rsize = rsize0;
 131     }
 132   else
 133     {
 134       if (rsize != NULL)
 135         *rsize = (insn & 0xff);
 136     }
 137   p += 4;
 138
 139   /* Next instruction must be asgeu V_SPILL,gr1,rab.  */
 140   insn = read_memory_integer (p, 4);
 141   if (insn != 0x5e40017e)
 142     {
 143       p = pc;
 144       goto done;
 145     }
 146   p += 4;
 147
 148   /* Next instruction usually sets the frame pointer (lr1) by adding
 149      <size * 4> from gr1.  However, this can (and high C does) be
 150      deferred until anytime before the first function call.  So it is
 151      OK if we don't see anything which sets lr1.  */
 152   /* Normally this is just add lr1,gr1,<size * 4>.  */
 153   insn = read_memory_integer (p, 4);
 154   if ((insn & 0xffffff00) == 0x15810100)
 155     p += 4;
 156   else
 157     {
 158       /* However, for large frames it can be
 159          const <reg>, <size *4>
 160          add lr1,gr1,<reg>
 161          */
 162       int reg;
 163       CORE_ADDR q;
 164
 165       if ((insn & 0xff000000) == 0x03000000)
 166         {
 167           reg = (insn >> 8) & 0xff;
 168           q = p + 4;
 169           insn = read_memory_integer (q, 4);
 170           if ((insn & 0xffffff00) == 0x14810100
 171               && (insn & 0xff) == reg)
 172             p = q;
 173         }
 174     }
 175
 176   /* Next comes "add lr{<rsize-1>},msp,0", but only if a memory
 177      frame pointer is in use.  We just check for add lr<anything>,msp,0;
 178      we don't check this rsize against the first instruction, and
 179      we don't check that the trace-back tag indicates a memory frame pointer
 180      is in use.
 181
 182      The recommended instruction is actually "sll lr<whatever>,msp,0".
 183      We check for that, too.  Originally Jim Kingdon's code seemed
 184      to be looking for a "sub" instruction here, but the mask was set
 185      up to lose all the time. */
 186   insn = read_memory_integer (p, 4);
 187   if (((insn & 0xff80ffff) == 0x15807d00)       /* add */
 188    || ((insn & 0xff80ffff) == 0x81807d00) )     /* sll */
 189     {
 190       p += 4;
 191       if (mfp_used != NULL)
 192         *mfp_used = 1;
 193     }
 194
 195   /* Next comes a subtraction from msp to allocate a memory frame,
 196      but only if a memory frame is
 197      being used.  We don't check msize against the trace-back tag.
 198
 199      Normally this is just
 200      sub msp,msp,<msize>
 201      */
 202   insn = read_memory_integer (p, 4);
 203   if ((insn & 0xffffff00) == 0x257d7d00)
 204     {
 205       p += 4;
 206       if (msize != NULL)
 207         *msize = insn & 0xff;
 208     }
 209   else
 210     {
 211       /* For large frames, instead of a single instruction it might
 212          be
 213
 214          const <reg>, <msize>
 215          consth <reg>, <msize>     ; optional
 216          sub msp,msp,<reg>
 217          */
 218       int reg;
 219       unsigned msize0;
 220       CORE_ADDR q = p;
 221
 222       if ((insn & 0xff000000) == 0x03000000)
 223         {
 224           reg = (insn >> 8) & 0xff;
 225           msize0 = ((insn >> 8) & 0xff00) | (insn & 0xff);
 226           q += 4;
 227           insn = read_memory_integer (q, 4);
 228           /* Check for consth.  */
 229           if ((insn & 0xff000000) == 0x02000000
 230               && (insn & 0x0000ff00) == reg)
 231             {
 232               msize0 |= (insn << 8) & 0xff000000;
 233               msize0 |= (insn << 16) & 0x00ff0000;
 234               q += 4;
 235               insn = read_memory_integer (q, 4);
 236             }
 237           /* Check for sub msp,msp,<reg>.  */
 238           if ((insn & 0xffffff00) == 0x247d7d00
 239               && (insn & 0xff) == reg)
 240             {
 241               p = q + 4;
 242               if (msize != NULL)
 243                 *msize = msize0;
 244             }
 245         }
 246     }
 247
 248  done:
 249   if (misc_index >= 0)
 250     {
 251       if (mi == 0)
 252         {
 253           /* Add a new cache entry.  */
 254           mi = (struct prologue_info *)xmalloc (sizeof (struct prologue_info));
 255           misc_function_vector[misc_index].misc_info = (char *)mi;
 256           mi->rsize_valid = 0;
 257           mi->msize_valid = 0;
 258           mi->mfp_valid = 0;
 259         }
 260       /* else, cache entry exists, but info is incomplete.  */
 261       mi->pc = p;
 262       if (rsize != NULL)
 263         {
 264           mi->rsize = *rsize;
 265           mi->rsize_valid = 1;
 266         }
 267       if (msize != NULL)
 268         {
 269           mi->msize = *msize;
 270           mi->msize_valid = 1;
 271         }
 272       if (mfp_used != NULL)
 273         {
 274           mi->mfp_used = *mfp_used;
 275           mi->mfp_valid = 1;
 276         }
 277     }
 278   return p;
 279 }
 280
 281 /* Advance PC across any function entry prologue instructions
 282    to reach some "real" code.  */
 283
 284 CORE_ADDR
 285 skip_prologue (pc)
 286      CORE_ADDR pc;
 287 {
 288   return examine_prologue (pc, (unsigned *)NULL, (unsigned *)NULL,
 289                            (int *)NULL);
 290 }
 291
 292 /* Initialize the frame.  In addition to setting "extra" frame info,
 293    we also set ->frame because we use it in a nonstandard way, and ->pc
 294    because we need to know it to get the other stuff.  See the diagram
 295    of stacks and the frame cache in tm-29k.h for more detail.  */
 296 static void
 297 init_frame_info (innermost_frame, fci)
 298      int innermost_frame;
 299      struct frame_info *fci;
 300 {
 301   CORE_ADDR p;
 302   long insn;
 303   unsigned rsize;
 304   unsigned msize;
 305   int mfp_used;
 306   struct symbol *func;
 307
 308   p = fci->pc;
 309
 310   if (innermost_frame)
 311     fci->frame = read_register (GR1_REGNUM);
 312   else
 313     fci->frame = fci->next_frame + fci->next->rsize;
 314
 315 #if CALL_DUMMY_LOCATION == ON_STACK
 316   This wont work;
 317 #else
 318   if (PC_IN_CALL_DUMMY (p, 0, 0))
 319 #endif
 320     {
 321       fci->rsize = DUMMY_FRAME_RSIZE;
 322       /* This doesn't matter since we never try to get locals or args
 323          from a dummy frame.  */
 324       fci->msize = 0;
 325       /* Dummy frames always use a memory frame pointer.  */
 326       fci->saved_msp =
 327         read_register_stack_integer (fci->frame + DUMMY_FRAME_RSIZE - 4, 4);
 328       return;
 329     }
 330
 331   func = find_pc_function (p);
 332   if (func != NULL)
 333     p = BLOCK_START (SYMBOL_BLOCK_VALUE (func));
 334   else
 335     {
 336       /* Search backward to find the trace-back tag.  However,
 337          do not trace back beyond the start of the text segment
 338          (just as a sanity check to avoid going into never-never land).  */
 339       while (p >= text_start
 340              && ((insn = read_memory_integer (p, 4)) & 0xff000000) != 0)
 341         p -= 4;
 342
 343       if (p < text_start)
 344         {
 345           /* Couldn't find the trace-back tag.
 346              Something strange is going on.  */
 347           fci->saved_msp = 0;
 348           fci->rsize = 0;
 349           fci->msize = 0;
 350           return;
 351         }
 352       else
 353         /* Advance to the first word of the function, i.e. the word
 354            after the trace-back tag.  */
 355         p += 4;
 356     }
 357   /* We've found the start of the function.  Since High C interchanges
 358      the meanings of bits 23 and 22 (as of Jul 90), and we
 359      need to look at the prologue anyway to figure out
 360      what rsize is, ignore the contents of the trace-back tag.  */
 361   examine_prologue (p, &rsize, &msize, &mfp_used);
 362   fci->rsize = rsize;
 363   fci->msize = msize;
 364   if (innermost_frame)
 365     {
 366       fci->saved_msp = read_register (MSP_REGNUM) + msize;
 367     }
 368   else
 369     {
 370       if (mfp_used)
 371         fci->saved_msp =
 372           read_register_stack_integer (fci->frame + rsize - 1, 4);
 373       else
 374         fci->saved_msp = fci->next->saved_msp + msize;
 375     }
 376 }
 377
 378 void
 379 init_extra_frame_info (fci)
 380      struct frame_info *fci;
 381 {
 382   if (fci->next == 0)
 383     /* Assume innermost frame.  May produce strange results for "info frame"
 384        but there isn't any way to tell the difference.  */
 385     init_frame_info (1, fci);
 386   else
 387     /* We're in get_prev_frame_info.
 388        Take care of everything in init_frame_pc.  */
 389     ;
 390 }
 391
 392 void
 393 init_frame_pc (fromleaf, fci)
 394      int fromleaf;
 395      struct frame_info *fci;
 396 {
 397   fci->pc = (fromleaf ? SAVED_PC_AFTER_CALL (fci->next) :
 398              fci->next ? FRAME_SAVED_PC (fci->next) : read_pc ());
 399   init_frame_info (0, fci);
 400 }
 401 \f
 402 /* Local variables (i.e. LOC_LOCAL) are on the memory stack, with their
 403    offsets being relative to the memory stack pointer (high C) or
 404    saved_msp (gcc).  */
 405
 406 CORE_ADDR
 407 frame_locals_address (fi)
 408      struct frame_info *fi;
 409 {
 410   struct block *b = block_for_pc (fi->pc);
 411   /* If compiled without -g, assume GCC.  */
 412   if (b == NULL || BLOCK_GCC_COMPILED (b))
 413     return fi->saved_msp;
 414   else
 415     return fi->saved_msp - fi->msize;
 416 }
 417 \f
 418 /* Routines for reading the register stack.  The caller gets to treat
 419    the register stack as a uniform stack in memory, from address $gr1
 420    straight through $rfb and beyond.  */
 421
 422 /* Analogous to read_memory except the length is understood to be 4.
 423    Also, myaddr can be NULL (meaning don't bother to read), and
 424    if actual_mem_addr is non-NULL, store there the address that it
 425    was fetched from (or if from a register the offset within
 426    registers).  Set *LVAL to lval_memory or lval_register, depending
 427    on where it came from.  */
 428 void
 429 read_register_stack (memaddr, myaddr, actual_mem_addr, lval)
 430      CORE_ADDR memaddr;
 431      char *myaddr;
 432      CORE_ADDR *actual_mem_addr;
 433      enum lval_type *lval;
 434 {
 435   long rfb = read_register (RFB_REGNUM);
 436   long rsp = read_register (RSP_REGNUM);
 437   if (memaddr < rfb)
 438     {
 439       /* It's in a register.  */
 440       int regnum = (memaddr - rsp) / 4 + LR0_REGNUM;
 441       if (regnum < LR0_REGNUM || regnum > LR0_REGNUM + 127)
 442         error ("Attempt to read register stack out of range.");
 443       if (myaddr != NULL)
 444         read_register_gen (regnum, myaddr);
 445       if (lval != NULL)
 446         *lval = lval_register;
 447       if (actual_mem_addr != NULL)
 448         *actual_mem_addr = REGISTER_BYTE (regnum);
 449     }
 450   else
 451     {
 452       /* It's in the memory portion of the register stack.  */
 453       if (myaddr != NULL)
 454         read_memory (memaddr, myaddr, 4);
 455       if (lval != NULL)
 456         *lval = lval_memory;
 457       if (actual_mem_addr != NULL)
 458         *actual_mem_addr == memaddr;
 459     }
 460 }
 461
 462 /* Analogous to read_memory_integer
 463    except the length is understood to be 4.  */
 464 long
 465 read_register_stack_integer (memaddr, len)
 466      CORE_ADDR memaddr;
 467      int len;
 468 {
 469   long buf;
 470   read_register_stack (memaddr, &buf, NULL, NULL);
 471   SWAP_TARGET_AND_HOST (&buf, 4);
 472   return buf;
 473 }
 474
 475 /* Copy 4 bytes from GDB memory at MYADDR into inferior memory
 476    at MEMADDR and put the actual address written into in
 477    *ACTUAL_MEM_ADDR.  */
 478 static void
 479 write_register_stack (memaddr, myaddr, actual_mem_addr)
 480      CORE_ADDR memaddr;
 481      char *myaddr;
 482      CORE_ADDR *actual_mem_addr;
 483 {
 484   long rfb = read_register (RFB_REGNUM);
 485   long rsp = read_register (RSP_REGNUM);
 486   if (memaddr < rfb)
 487     {
 488       /* It's in a register.  */
 489       int regnum = (memaddr - rsp) / 4 + LR0_REGNUM;
 490       if (regnum < LR0_REGNUM || regnum > LR0_REGNUM + 127)
 491         error ("Attempt to read register stack out of range.");
 492       if (myaddr != NULL)
 493         write_register (regnum, *(long *)myaddr);
 494       if (actual_mem_addr != NULL)
 495         *actual_mem_addr = NULL;
 496     }
 497   else
 498     {
 499       /* It's in the memory portion of the register stack.  */
 500       if (myaddr != NULL)
 501         write_memory (memaddr, myaddr, 4);
 502       if (actual_mem_addr != NULL)
 503         *actual_mem_addr == memaddr;
 504     }
 505 }
 506 \f
 507 /* Find register number REGNUM relative to FRAME and put its
 508    (raw) contents in *RAW_BUFFER.  Set *OPTIMIZED if the variable
 509    was optimized out (and thus can't be fetched).  If the variable
 510    was fetched from memory, set *ADDRP to where it was fetched from,
 511    otherwise it was fetched from a register.
 512
 513    The argument RAW_BUFFER must point to aligned memory.  */
 514 void
 515 get_saved_register (raw_buffer, optimized, addrp, frame, regnum, lvalp)
 516      char *raw_buffer;
 517      int *optimized;
 518      CORE_ADDR *addrp;
 519      FRAME frame;
 520      int regnum;
 521      enum lval_type *lvalp;
 522 {
 523   struct frame_info *fi = get_frame_info (frame);
 524   CORE_ADDR addr;
 525   enum lval_type lval;
 526
 527   /* Once something has a register number, it doesn't get optimized out.  */
 528   if (optimized != NULL)
 529     *optimized = 0;
 530   if (regnum == RSP_REGNUM)
 531     {
 532       if (raw_buffer != NULL)
 533         *(CORE_ADDR *)raw_buffer = fi->frame;
 534       if (lvalp != NULL)
 535         *lvalp = not_lval;
 536       return;
 537     }
 538   else if (regnum == PC_REGNUM)
 539     {
 540       if (raw_buffer != NULL)
 541         *(CORE_ADDR *)raw_buffer = fi->pc;
 542
 543       /* Not sure we have to do this.  */
 544       if (lvalp != NULL)
 545         *lvalp = not_lval;
 546
 547       return;
 548     }
 549   else if (regnum == MSP_REGNUM)
 550     {
 551       if (raw_buffer != NULL)
 552         {
 553           if (fi->next != NULL)
 554             *(CORE_ADDR *)raw_buffer = fi->next->saved_msp;
 555           else
 556             *(CORE_ADDR *)raw_buffer = read_register (MSP_REGNUM);
 557         }
 558       /* The value may have been computed, not fetched.  */
 559       if (lvalp != NULL)
 560         *lvalp = not_lval;
 561       return;
 562     }
 563   else if (regnum < LR0_REGNUM || regnum >= LR0_REGNUM + 128)
 564     {
 565       /* These registers are not saved over procedure calls,
 566          so just print out the current values.  */
 567       if (raw_buffer != NULL)
 568         *(CORE_ADDR *)raw_buffer = read_register (regnum);
 569       if (lvalp != NULL)
 570         *lvalp = lval_register;
 571       if (addrp != NULL)
 572         *addrp = REGISTER_BYTE (regnum);
 573       return;
 574     }
 575
 576   addr = fi->frame + (regnum - LR0_REGNUM) * 4;
 577   if (raw_buffer != NULL)
 578     read_register_stack (addr, raw_buffer, &addr, &lval);
 579   if (lvalp != NULL)
 580     *lvalp = lval;
 581   if (addrp != NULL)
 582     *addrp = addr;
 583 }
 584 \f
 585 /* Discard from the stack the innermost frame,
 586    restoring all saved registers.  */
 587
 588 void
 589 pop_frame ()
 590 {
 591   FRAME frame = get_current_frame ();
 592   struct frame_info *fi = get_frame_info (frame);
 593   CORE_ADDR rfb = read_register (RFB_REGNUM);
 594   CORE_ADDR gr1 = fi->frame + fi->rsize;
 595   CORE_ADDR lr1;
 596   CORE_ADDR ret_addr;
 597   int i;
 598
 599   /* If popping a dummy frame, need to restore registers.  */
 600   if (PC_IN_CALL_DUMMY (read_register (PC_REGNUM),
 601                         read_register (SP_REGNUM),
 602                         FRAME_FP (fi)))
 603     {
 604       for (i = 0; i < DUMMY_SAVE_SR128; ++i)
 605         write_register
 606           (SR_REGNUM (i + 128),
 607            read_register (LR0_REGNUM + DUMMY_ARG / 4 + i));
 608       for (i = 0; i < DUMMY_SAVE_GR96; ++i)
 609         write_register
 610           (GR96_REGNUM + i,
 611            read_register (LR0_REGNUM + DUMMY_ARG / 4 + DUMMY_SAVE_SR128 + i));
 612     }
 613
 614   /* Restore the memory stack pointer.  */
 615   write_register (MSP_REGNUM, fi->saved_msp);
 616   /* Restore the register stack pointer.  */
 617   write_register (GR1_REGNUM, gr1);
 618   /* Check whether we need to fill registers.  */
 619   lr1 = read_register (LR0_REGNUM + 1);
 620   if (lr1 > rfb)
 621     {
 622       /* Fill.  */
 623       int num_bytes = lr1 - rfb;
 624       int i;
 625       long word;
 626       write_register (RAB_REGNUM, read_register (RAB_REGNUM) + num_bytes);
 627       write_register (RFB_REGNUM, lr1);
 628       for (i = 0; i < num_bytes; i += 4)
 629         {
 630           /* Note: word is in host byte order.  */
 631           word = read_memory_integer (rfb + i, 4);
 632           write_register (LR0_REGNUM + ((rfb - gr1) % 0x80) + i / 4, word);
 633         }
 634     }
 635   ret_addr = read_register (LR0_REGNUM);
 636   write_register (PC_REGNUM, ret_addr);
 637   write_register (NPC_REGNUM, ret_addr + 4);
 638   flush_cached_frames ();
 639   set_current_frame (create_new_frame (0, read_pc()));
 640 }
 641
 642 /* Push an empty stack frame, to record the current PC, etc.  */
 643
 644 void
 645 push_dummy_frame ()
 646 {
 647   long w;
 648   CORE_ADDR rab, gr1;
 649   CORE_ADDR msp = read_register (MSP_REGNUM);
 650   int i;
 651
 652   /* Save the PC.  */
 653   write_register (LR0_REGNUM, read_register (PC_REGNUM));
 654
 655   /* Allocate the new frame.  */
 656   gr1 = read_register (GR1_REGNUM) - DUMMY_FRAME_RSIZE;
 657   write_register (GR1_REGNUM, gr1);
 658
 659   rab = read_register (RAB_REGNUM);
 660   if (gr1 < rab)
 661     {
 662       /* We need to spill registers.  */
 663       int num_bytes = rab - gr1;
 664       CORE_ADDR rfb = read_register (RFB_REGNUM);
 665       int i;
 666       long word;
 667
 668       write_register (RFB_REGNUM, rfb - num_bytes);
 669       write_register (RAB_REGNUM, gr1);
 670       for (i = 0; i < num_bytes; i += 4)
 671         {
 672           /* Note:  word is in target byte order.  */
 673           read_register_gen (LR0_REGNUM + i / 4, &word, 4);
 674           write_memory (rfb - num_bytes + i, &word, 4);
 675         }
 676     }
 677
 678   /* There are no arguments in to the dummy frame, so we don't need
 679      more than rsize plus the return address and lr1.  */
 680   write_register (LR0_REGNUM + 1, gr1 + DUMMY_FRAME_RSIZE + 2 * 4);
 681
 682   /* Set the memory frame pointer.  */
 683   write_register (LR0_REGNUM + DUMMY_FRAME_RSIZE / 4 - 1, msp);
 684
 685   /* Allocate arg_slop.  */
 686   write_register (MSP_REGNUM, msp - 16 * 4);
 687
 688   /* Save registers.  */
 689   for (i = 0; i < DUMMY_SAVE_SR128; ++i)
 690     write_register (LR0_REGNUM + DUMMY_ARG / 4 + i,
 691                     read_register (SR_REGNUM (i + 128)));
 692   for (i = 0; i < DUMMY_SAVE_GR96; ++i)
 693     write_register (LR0_REGNUM + DUMMY_ARG / 4 + DUMMY_SAVE_SR128 + i,
 694                     read_register (GR96_REGNUM + i));
 695 }