path: root/gdb/mips-tdep.c

/* Target-dependent code for the MIPS architecture, for GDB, the GNU Debugger.
   Copyright 1988, 1989, 1990, 1991  Free Software Foundation, Inc.
   Contributed by Alessandro Forin(af@cs.cmu.edu) at CMU
   and by Per Bothner(bothner@cs.wisc.edu) at U.Wisconsin.

This file is part of GDB.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include <stdio.h>
#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "symtab.h"
#include "value.h"
#include "gdbcmd.h"
#include "language.h"

#ifdef USG
#include <sys/types.h>
#endif

#include <sys/param.h>
#include <sys/dir.h>
#include <signal.h>
#include <sys/ioctl.h>

#include "gdbcore.h"

#ifndef	MIPSMAGIC
#ifdef MIPSEL
#define MIPSMAGIC	MIPSELMAGIC
#else
#define MIPSMAGIC	MIPSEBMAGIC
#endif
#endif

#define VM_MIN_ADDRESS (unsigned)0x400000

#include <sys/user.h>		/* After a.out.h  */
#include <sys/file.h>
#include <sys/stat.h>


#define PROC_LOW_ADDR(proc) ((proc)->adr) /* least address */
#define PROC_HIGH_ADDR(proc) ((proc)->pad2) /* upper address bound */
#define PROC_FRAME_OFFSET(proc) ((proc)->framesize)
#define PROC_FRAME_REG(proc) ((proc)->framereg)
#define PROC_REG_MASK(proc) ((proc)->regmask)
#define PROC_FREG_MASK(proc) ((proc)->fregmask)
#define PROC_REG_OFFSET(proc) ((proc)->regoffset)
#define PROC_FREG_OFFSET(proc) ((proc)->fregoffset)
#define PROC_PC_REG(proc) ((proc)->pcreg)
#define PROC_SYMBOL(proc) (*(struct symbol**)&(proc)->isym)
#define _PROC_MAGIC_ 0x0F0F0F0F
#define PROC_DESC_IS_DUMMY(proc) ((proc)->isym == _PROC_MAGIC_)
#define SET_PROC_DESC_IS_DUMMY(proc) ((proc)->isym = _PROC_MAGIC_)

struct linked_proc_info
{
  struct mips_extra_func_info info;
  struct linked_proc_info *next;
} * linked_proc_desc_table = NULL;


#define READ_FRAME_REG(fi, regno) read_next_frame_reg((fi)->next, regno)

int
read_next_frame_reg(fi, regno)
     FRAME fi;
     int regno;
{
#define SIGFRAME_BASE   sizeof(struct sigcontext)
#define SIGFRAME_PC_OFF (-SIGFRAME_BASE+ 2*sizeof(int))
#define SIGFRAME_SP_OFF (-SIGFRAME_BASE+32*sizeof(int))
#define SIGFRAME_RA_OFF (-SIGFRAME_BASE+34*sizeof(int))
  for (; fi; fi = fi->next)
      if (in_sigtramp(fi->pc, 0)) {
	  /* No idea if this code works. --PB. */
	  int offset;
	  if (regno == PC_REGNUM) offset = SIGFRAME_PC_OFF;
	  else if (regno == RA_REGNUM) offset = SIGFRAME_RA_OFF;
	  else if (regno == SP_REGNUM) offset = SIGFRAME_SP_OFF;
	  else return 0;
	  return read_memory_integer(fi->frame + offset, 4);
      }
      else if (regno == SP_REGNUM) return fi->frame;
      else if (fi->saved_regs->regs[regno])
	return read_memory_integer(fi->saved_regs->regs[regno], 4);
  return read_register(regno);
}

int
mips_frame_saved_pc(frame)
     FRAME frame;
{
  mips_extra_func_info_t proc_desc = (mips_extra_func_info_t)frame->proc_desc;
  int pcreg = proc_desc ? PROC_PC_REG(proc_desc) : RA_REGNUM;
  if (proc_desc && PROC_DESC_IS_DUMMY(proc_desc))
      return read_memory_integer(frame->frame - 4, 4);
#if 0
  /* If in the procedure prologue, RA_REGNUM might not have been saved yet.
   * Assume non-leaf functions start with:
   *	addiu $sp,$sp,-frame_size
   *	sw $ra,ra_offset($sp)
   * This if the pc is pointing at either of these instructions,
   * then $ra hasn't been trashed.
   * If the pc has advanced beyond these two instructions,
   * then $ra has been saved.
   * critical, and much more complex. Handling $ra is enough to get
   * a stack trace, but some register values with be wrong.
   */
  if (frame->proc_desc && frame->pc < PROC_LOW_ADDR(proc_desc) + 8)
      return read_register(pcreg);
#endif
  return read_next_frame_reg(frame, pcreg);
}

static struct mips_extra_func_info temp_proc_desc;
static struct frame_saved_regs temp_saved_regs;

CORE_ADDR heuristic_proc_start(pc)
    CORE_ADDR pc;
{

    CORE_ADDR start_pc = pc;
    CORE_ADDR fence = start_pc - 10000;
    if (fence < VM_MIN_ADDRESS) fence = VM_MIN_ADDRESS;
    /* search back for previous return */
    for (start_pc -= 4; ; start_pc -= 4)
	if (start_pc < fence) return 0; 
	else if (ABOUT_TO_RETURN(start_pc))
	    break;

    start_pc += 8; /* skip return, and its delay slot */
#if 0
    /* skip nops (usually 1) 0 - is this */
    while (start_pc < pc && read_memory_integer (start_pc, 4) == 0)
	start_pc += 4;
#endif
    return start_pc;
}

mips_extra_func_info_t
heuristic_proc_desc(start_pc, limit_pc, next_frame)
    CORE_ADDR start_pc, limit_pc;
    FRAME next_frame;
{
    CORE_ADDR sp = next_frame ? next_frame->frame : read_register (SP_REGNUM);
    CORE_ADDR cur_pc;
    int frame_size;
    int has_frame_reg = 0;
    int reg30; /* Value of $r30. Used by gcc for frame-pointer */
    unsigned long reg_mask = 0;

    if (start_pc == 0) return NULL;
    bzero(&temp_proc_desc, sizeof(temp_proc_desc));
    bzero(&temp_saved_regs, sizeof(struct frame_saved_regs));
    if (start_pc + 200 < limit_pc) limit_pc = start_pc + 200;
  restart:
    frame_size = 0;
    for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += 4) {
	unsigned long word;
	int status;

	status = read_memory_nobpt (cur_pc, &word, 4); 
	if (status) memory_error (status, cur_pc); 
	if ((word & 0xFFFF0000) == 0x27bd0000) /* addiu $sp,$sp,-i */
	    frame_size += (-word) & 0xFFFF;
	else if ((word & 0xFFFF0000) == 0x23bd0000) /* addu $sp,$sp,-i */
	    frame_size += (-word) & 0xFFFF;
	else if ((word & 0xFFE00000) == 0xafa00000) { /* sw reg,offset($sp) */
	    int reg = (word & 0x001F0000) >> 16;
	    reg_mask |= 1 << reg;
	    temp_saved_regs.regs[reg] = sp + (short)word;
	}
	else if ((word & 0xFFFF0000) == 0x27be0000) { /* addiu $30,$sp,size */
	    if ((unsigned short)word != frame_size)
		reg30 = sp + (unsigned short)word;
	    else if (!has_frame_reg) {
		int alloca_adjust;
		has_frame_reg = 1;
		reg30 = read_next_frame_reg(next_frame, 30);
		alloca_adjust = reg30 - (sp + (unsigned short)word);
		if (alloca_adjust > 0) {
		    /* FP > SP + frame_size. This may be because
		    /* of an alloca or somethings similar.
		     * Fix sp to "pre-alloca" value, and try again.
		     */
		    sp += alloca_adjust;
		    goto restart;
		}
	    }
	}
	else if ((word & 0xFFE00000) == 0xafc00000) { /* sw reg,offset($30) */
	    int reg = (word & 0x001F0000) >> 16;
	    reg_mask |= 1 << reg;
	    temp_saved_regs.regs[reg] = reg30 + (short)word;
	}
    }
    if (has_frame_reg) {
	PROC_FRAME_REG(&temp_proc_desc) = 30;
	PROC_FRAME_OFFSET(&temp_proc_desc) = 0;
    }
    else {
	PROC_FRAME_REG(&temp_proc_desc) = SP_REGNUM;
	PROC_FRAME_OFFSET(&temp_proc_desc) = frame_size;
    }
    PROC_REG_MASK(&temp_proc_desc) = reg_mask;
    PROC_PC_REG(&temp_proc_desc) = RA_REGNUM;
    return &temp_proc_desc;
}

mips_extra_func_info_t
find_proc_desc(pc, next_frame)
    CORE_ADDR pc;
    FRAME next_frame;
{
  mips_extra_func_info_t proc_desc;
  extern struct block *block_for_pc();
  struct block   *b = block_for_pc(pc);

  struct symbol *sym =
      b ? lookup_symbol(".gdbinfo.", b, LABEL_NAMESPACE, 0, NULL) : NULL;
  if (sym != NULL)
    {
	/* IF this is the topmost frame AND
	 * (this proc does not have debugging information OR
	 * the PC is in the procedure prologue)
	 * THEN create a "hueristic" proc_desc (by analyzing
	 * the actual code) to replace the "official" proc_desc.
	 */
	proc_desc = (struct mips_extra_func_info *)sym->value.value;
	if (next_frame == NULL) {
	    struct symtab_and_line val;
	    struct symbol *proc_symbol =
		PROC_DESC_IS_DUMMY(proc_desc) ? 0 : PROC_SYMBOL(proc_desc);
	    if (proc_symbol) {
		val = find_pc_line (BLOCK_START
				    (SYMBOL_BLOCK_VALUE(proc_symbol)),
				    0);
		val.pc = val.end ? val.end : pc;
	    }
	    if (!proc_symbol || pc < val.pc) {
		mips_extra_func_info_t found_heuristic =
		    heuristic_proc_desc(PROC_LOW_ADDR(proc_desc),
					pc, next_frame);
		if (found_heuristic) proc_desc = found_heuristic;
	    }
	}
    }
  else
    {
      register struct linked_proc_info *link;
      for (link = linked_proc_desc_table; link; link = link->next)
	  if (PROC_LOW_ADDR(&link->info) <= pc
	      && PROC_HIGH_ADDR(&link->info) > pc)
	      return &link->info;
      proc_desc =
	  heuristic_proc_desc(heuristic_proc_start(pc), pc, next_frame);
    }
  return proc_desc;
}

mips_extra_func_info_t cached_proc_desc;

FRAME_ADDR mips_frame_chain(frame)
    FRAME frame;
{
    extern CORE_ADDR startup_file_start;	/* From blockframe.c */
    mips_extra_func_info_t proc_desc;
    CORE_ADDR saved_pc = FRAME_SAVED_PC(frame);
    if (startup_file_start)
      { /* has at least the __start symbol */
	if (saved_pc == 0 || !outside_startup_file (saved_pc)) return 0;
      }
    else
      { /* This hack depends on the internals of __start. */
	/* We also assume the breakpoints are *not* inserted */
        if (saved_pc == 0
	    || read_memory_integer (saved_pc + 8, 4) & 0xFC00003F == 0xD)
	    return 0;  /* break */
      }
    proc_desc = find_proc_desc(saved_pc, frame);
    if (!proc_desc) return 0;
    cached_proc_desc = proc_desc;
    return read_next_frame_reg(frame, PROC_FRAME_REG(proc_desc))
	+ PROC_FRAME_OFFSET(proc_desc);
}

void
init_extra_frame_info(fci)
     struct frame_info *fci;
{
  extern struct obstack frame_cache_obstack;
  /* Use proc_desc calculated in frame_chain */
  mips_extra_func_info_t proc_desc = fci->next ? cached_proc_desc :
      find_proc_desc(fci->pc, fci->next);
  fci->saved_regs = (struct frame_saved_regs*)
    obstack_alloc (&frame_cache_obstack, sizeof(struct frame_saved_regs));
  bzero(fci->saved_regs, sizeof(struct frame_saved_regs));
  fci->proc_desc =
      proc_desc == &temp_proc_desc ? (char*)NULL : (char*)proc_desc;
  if (proc_desc)
    {
      int ireg;
      CORE_ADDR reg_position;
      unsigned long mask;
      /* r0 bit means kernel trap */
      int kernel_trap = PROC_REG_MASK(proc_desc) & 1;

      /* Fixup frame-pointer - only needed for top frame */
      /* This may not be quite right, if procedure has a real frame register */
      if (fci->pc == PROC_LOW_ADDR(proc_desc))
	  fci->frame = read_register (SP_REGNUM);
      else
	  fci->frame = READ_FRAME_REG(fci, PROC_FRAME_REG(proc_desc))
	      + PROC_FRAME_OFFSET(proc_desc);

      if (proc_desc == &temp_proc_desc)
	  *fci->saved_regs = temp_saved_regs;
      else
      {
	  /* find which general-purpose registers were saved */
	  reg_position = fci->frame + PROC_REG_OFFSET(proc_desc);
	  mask = kernel_trap ? 0xFFFFFFFF : PROC_REG_MASK(proc_desc);
	  for (ireg= 31; mask; --ireg, mask <<= 1)
	      if (mask & 0x80000000)
	      {
		  fci->saved_regs->regs[ireg] = reg_position;
		  reg_position -= 4;
	      }
	  /* find which floating-point registers were saved */
	  reg_position = fci->frame + PROC_FREG_OFFSET(proc_desc);
	  /* The freg_offset points to where the first *double* register is saved.
	   * So skip to the high-order word. */
	  reg_position += 4;
	  mask = kernel_trap ? 0xFFFFFFFF : PROC_FREG_MASK(proc_desc);
	  for (ireg = 31; mask; --ireg, mask <<= 1)
	      if (mask & 0x80000000)
	      {
		  fci->saved_regs->regs[32+ireg] = reg_position;
		  reg_position -= 4;
	      }
      }

      /* hack: if argument regs are saved, guess these contain args */
      if ((PROC_REG_MASK(proc_desc) & 0xF0) == 0) fci->num_args = -1;
      else if ((PROC_REG_MASK(proc_desc) & 0x80) == 0) fci->num_args = 4;
      else if ((PROC_REG_MASK(proc_desc) & 0x40) == 0) fci->num_args = 3;
      else if ((PROC_REG_MASK(proc_desc) & 0x20) == 0) fci->num_args = 2;
      else if ((PROC_REG_MASK(proc_desc) & 0x10) == 0) fci->num_args = 1;

      fci->saved_regs->regs[PC_REGNUM] = fci->saved_regs->regs[RA_REGNUM];
    }
  if (fci->next == 0)
      supply_register(FP_REGNUM, &fci->frame);
}


CORE_ADDR mips_push_arguments(nargs, args, sp, struct_return, struct_addr)
  int nargs;
  value *args;
  CORE_ADDR sp;
  int struct_return;
  CORE_ADDR struct_addr;
{
  CORE_ADDR buf;
  register i;
  int accumulate_size = struct_return ? 4 : 0;
  struct mips_arg { char *contents; int len; int offset; };
  struct mips_arg *mips_args =
      (struct mips_arg*)alloca(nargs * sizeof(struct mips_arg));
  register struct mips_arg *m_arg;
  for (i = 0, m_arg = mips_args; i < nargs; i++, m_arg++) {
    extern value value_arg_coerce();
    value arg = value_arg_coerce (args[i]);
    m_arg->len = TYPE_LENGTH (VALUE_TYPE (arg));
    /* This entire mips-specific routine is because doubles must be aligned
     * on 8-byte boundaries. It still isn't quite right, because MIPS decided
     * to align 'struct {int a, b}' on 4-byte boundaries (even though this
     * breaks their varargs implementation...). A correct solution
     * requires an simulation of gcc's 'alignof' (and use of 'alignof'
     * in stdarg.h/varargs.h).
     */
    if (m_arg->len > 4) accumulate_size = (accumulate_size + 7) & -8;
    m_arg->offset = accumulate_size;
    accumulate_size = (accumulate_size + m_arg->len + 3) & -4;
    m_arg->contents = VALUE_CONTENTS(arg);
  }
  accumulate_size = (accumulate_size + 7) & (-8);
  if (accumulate_size < 16) accumulate_size = 16; 
  sp -= accumulate_size;
  for (i = nargs; m_arg--, --i >= 0; )
    write_memory(sp + m_arg->offset, m_arg->contents, m_arg->len);
  if (struct_return) {
    buf = struct_addr;
    write_memory(sp, &buf, sizeof(CORE_ADDR));
}
  return sp;
}

/* MASK(i,j) == (1<<i) + (1<<(i+1)) + ... + (1<<j)). Assume i<=j<31. */
#define MASK(i,j) ((1 << (j)+1)-1 ^ (1 << (i))-1)

void
mips_push_dummy_frame()
{
  int ireg;
  struct linked_proc_info *link = (struct linked_proc_info*)
      xmalloc(sizeof(struct linked_proc_info));
  mips_extra_func_info_t proc_desc = &link->info;
  CORE_ADDR sp = read_register (SP_REGNUM);
  CORE_ADDR save_address;
  REGISTER_TYPE buffer;
  link->next = linked_proc_desc_table;
  linked_proc_desc_table = link;
#define PUSH_FP_REGNUM 16 /* must be a register preserved across calls */
#define GEN_REG_SAVE_MASK MASK(1,16)|MASK(24,28)|(1<<31)
#define GEN_REG_SAVE_COUNT 22
#define FLOAT_REG_SAVE_MASK MASK(0,19)
#define FLOAT_REG_SAVE_COUNT 20
#define SPECIAL_REG_SAVE_COUNT 4
  /*
   * The registers we must save are all those not preserved across
   * procedure calls. Dest_Reg (see tm-mips.h) must also be saved.
   * In addition, we must save the PC, and PUSH_FP_REGNUM.
   * (Ideally, we should also save MDLO/-HI and FP Control/Status reg.)
   *
   * Dummy frame layout:
   *  (high memory)
   * 	Saved PC
   *	Saved MMHI, MMLO, FPC_CSR
   *	Saved R31
   *	Saved R28
   *	...
   *	Saved R1
   *    Saved D18 (i.e. F19, F18)
   *    ...
   *    Saved D0 (i.e. F1, F0)
   *	CALL_DUMMY (subroutine stub; see m-mips.h)
   *	Parameter build area (not yet implemented)
   *  (low memory)
   */
  PROC_REG_MASK(proc_desc) = GEN_REG_SAVE_MASK;
  PROC_FREG_MASK(proc_desc) = FLOAT_REG_SAVE_MASK;
  PROC_REG_OFFSET(proc_desc) = /* offset of (Saved R31) from FP */
      -sizeof(long) - 4 * SPECIAL_REG_SAVE_COUNT;
  PROC_FREG_OFFSET(proc_desc) = /* offset of (Saved D18) from FP */
      -sizeof(double) - 4 * (SPECIAL_REG_SAVE_COUNT + GEN_REG_SAVE_COUNT);
  /* save general registers */
  save_address = sp + PROC_REG_OFFSET(proc_desc);
  for (ireg = 32; --ireg >= 0; )
    if (PROC_REG_MASK(proc_desc) & (1 << ireg))
      {
	buffer = read_register (ireg);
	write_memory (save_address, &buffer, sizeof(REGISTER_TYPE));
	save_address -= 4;
      }
  /* save floating-points registers */
  save_address = sp + PROC_FREG_OFFSET(proc_desc);
  for (ireg = 32; --ireg >= 0; )
    if (PROC_FREG_MASK(proc_desc) & (1 << ireg))
      {
	buffer = read_register (ireg + FP0_REGNUM);
	write_memory (save_address, &buffer, 4);
	save_address -= 4;
      }
  write_register (PUSH_FP_REGNUM, sp);
  PROC_FRAME_REG(proc_desc) = PUSH_FP_REGNUM;
  PROC_FRAME_OFFSET(proc_desc) = 0;
  buffer = read_register (PC_REGNUM);
  write_memory (sp - 4, &buffer, sizeof(REGISTER_TYPE));
  buffer = read_register (HI_REGNUM);
  write_memory (sp - 8, &buffer, sizeof(REGISTER_TYPE));
  buffer = read_register (LO_REGNUM);
  write_memory (sp - 12, &buffer, sizeof(REGISTER_TYPE));
  buffer = read_register (FCRCS_REGNUM);
  write_memory (sp - 16, &buffer, sizeof(REGISTER_TYPE));
  sp -= 4 * (GEN_REG_SAVE_COUNT+FLOAT_REG_SAVE_COUNT+SPECIAL_REG_SAVE_COUNT);
  write_register (SP_REGNUM, sp);
  PROC_LOW_ADDR(proc_desc) = sp - CALL_DUMMY_SIZE + CALL_DUMMY_START_OFFSET;
  PROC_HIGH_ADDR(proc_desc) = sp;
  SET_PROC_DESC_IS_DUMMY(proc_desc);
  PROC_PC_REG(proc_desc) = RA_REGNUM;
}

void
mips_pop_frame()
{ register int regnum;
  FRAME frame = get_current_frame ();
  CORE_ADDR new_sp = frame->frame;
  mips_extra_func_info_t proc_desc = (mips_extra_func_info_t)frame->proc_desc;
  if (PROC_DESC_IS_DUMMY(proc_desc))
    {
      struct linked_proc_info **ptr = &linked_proc_desc_table;;
      for (; &ptr[0]->info != proc_desc; ptr = &ptr[0]->next )
	  if (ptr[0] == NULL) abort();
      *ptr = ptr[0]->next;
      free (ptr[0]);
      write_register (HI_REGNUM, read_memory_integer(new_sp - 8, 4));
      write_register (LO_REGNUM, read_memory_integer(new_sp - 12, 4));
      write_register (FCRCS_REGNUM, read_memory_integer(new_sp - 16, 4));
    }
  write_register (PC_REGNUM, FRAME_SAVED_PC(frame));
  if (frame->proc_desc) {
    for (regnum = 32; --regnum >= 0; )
      if (PROC_REG_MASK(proc_desc) & (1 << regnum))
	write_register (regnum,
		  read_memory_integer (frame->saved_regs->regs[regnum], 4));
    for (regnum = 32; --regnum >= 0; )
      if (PROC_FREG_MASK(proc_desc) & (1 << regnum))
	write_register (regnum + FP0_REGNUM,
		  read_memory_integer (frame->saved_regs->regs[regnum + FP0_REGNUM], 4));
  }
  write_register (SP_REGNUM, new_sp);
  flush_cached_frames ();
  set_current_frame (create_new_frame (new_sp, read_pc ()));
}

static
mips_print_register(regnum, all)
     int regnum, all;
{
      unsigned char raw_buffer[8];
      REGISTER_TYPE val;

      read_relative_register_raw_bytes (regnum, raw_buffer);

      if (!(regnum & 1) && regnum >= FP0_REGNUM && regnum < FP0_REGNUM+32) {
	  read_relative_register_raw_bytes (regnum+1, raw_buffer+4);
	  printf_filtered ("(d%d: ", regnum&31);
	  val_print (builtin_type_double, raw_buffer, 0,
		     stdout, 0, 1, 0, Val_pretty_default);
	  printf_filtered ("); ", regnum&31);
      }
      fputs_filtered (reg_names[regnum], stdout);
#ifndef NUMERIC_REG_NAMES
      if (regnum < 32)
	  printf_filtered ("(r%d): ", regnum);
      else
#endif
	  printf_filtered (": ");

      /* If virtual format is floating, print it that way.  */
      if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT
	  && ! INVALID_FLOAT (raw_buffer, REGISTER_VIRTUAL_SIZE(regnum))) {
	  val_print (REGISTER_VIRTUAL_TYPE (regnum), raw_buffer, 0,
		     stdout, 0, 1, 0, Val_pretty_default);
      }
      /* Else print as integer in hex.  */
      else
	{
	  long val;

	  bcopy (raw_buffer, &val, sizeof (long));
	  if (val == 0)
	    printf_filtered ("0");
	  else if (all)
	    printf_filtered (local_hex_format(), val);
	  else
	    printf_filtered ("%s=%d", local_hex_string(val), val);
	}
}

/* Replacement for generic do_registers_info.  */
mips_do_registers_info (regnum, fpregs)
     int regnum;
     int fpregs;
{
  if (regnum != -1) {
      mips_print_register (regnum, 0);
      printf_filtered ("\n");
  }
  else {
      for (regnum = 0; regnum < NUM_REGS; ) {
	  if ((!fpregs) && regnum >= FP0_REGNUM && regnum <= FCRIR_REGNUM) {
	    regnum++;
	    continue;
	  }
	  mips_print_register (regnum, 1);
	  regnum++;
	  if ((regnum & 3) == 0 || regnum == NUM_REGS)
	      printf_filtered (";\n");
	  else
	      printf_filtered ("; ");
      }
  }
}
/* Return number of args passed to a frame. described by FIP.
   Can return -1, meaning no way to tell.  */

mips_frame_num_args(fip)
	FRAME fip;
{
#if 0
	struct chain_info_t *p;

	p = mips_find_cached_frame(FRAME_FP(fip));
	if (p->valid)
		return p->the_info.numargs;
#endif
	return -1;
}


/* Bad floats: Returns 0 if P points to a valid IEEE floating point number,
   1 if P points to a denormalized number or a NaN. LEN says whether this is
   a single-precision or double-precision float */
#define SINGLE_EXP_BITS  8
#define DOUBLE_EXP_BITS 11
int
isa_NAN(p, len)
     int *p, len;
{
  int exponent;
  if (len == 4)
    {
      exponent = *p;
      exponent = exponent << 1 >> (32 - SINGLE_EXP_BITS - 1);
      return ((exponent == -1) || (! exponent && *p));
    }
  else if (len == 8)
    {
      exponent = *(p+1);
      exponent = exponent << 1 >> (32 - DOUBLE_EXP_BITS - 1);
      return ((exponent == -1) || (! exponent && *p * *(p+1)));
    }
  else return 1;
}

/* To skip prologues, I use this predicate. Returns either PC
   itself if the code at PC does not look like a function prologue,
   PC+4 if it does (our caller does not need anything more fancy). */

CORE_ADDR mips_skip_prologue(pc)
     CORE_ADDR pc;
{
    struct symbol *f;
    struct block *b;
    unsigned long inst;

    /* For -g modules and most functions anyways the
       first instruction adjusts the stack. */
    inst = read_memory_integer(pc, 4);
    if ((inst & 0xffff0000) == 0x27bd0000)
	return pc + 4;

    /* Well, it looks like a frameless. Let's make sure.
       Note that we are not called on the current PC,
       but on the function`s start PC, and I have definitely
       seen optimized code that adjusts the SP quite later */
    b = block_for_pc(pc);
    if (!b) return pc;

    f = lookup_symbol(".gdbinfo.", b, LABEL_NAMESPACE, 0, NULL);
    if (!f) return pc;
    /* Ideally, I would like to use the adjusted info
       from mips_frame_info(), but for all practical
       purposes it will not matter (and it would require
       a different definition of SKIP_PROLOGUE())

       Actually, it would not hurt to skip the storing
       of arguments on the stack as well. */
    if (((struct mips_extra_func_info *)f->value.value)->framesize)
	return pc + 4;

    return pc;
}