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[deliverable/binutils-gdb.git] / gdb / mips-tdep.c

/* Target-dependent code for the MIPS architecture, for GDB, the GNU Debugger.
   Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998
   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., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdb_string.h"
#include "frame.h"
#include "inferior.h"
#include "symtab.h"
#include "value.h"
#include "gdbcmd.h"
#include "language.h"
#include "gdbcore.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbtypes.h"
#include "target.h"

#include "opcode/mips.h"

struct frame_extra_info
  {
    mips_extra_func_info_t proc_desc;
    int num_args;
  };

/* Some MIPS boards don't support floating point while others only
   support single-precision floating-point operations.  See also
   FP_REGISTER_DOUBLE. */

enum mips_fpu_type
  {
    MIPS_FPU_DOUBLE,            /* Full double precision floating point.  */
    MIPS_FPU_SINGLE,            /* Single precision floating point (R4650).  */
    MIPS_FPU_NONE               /* No floating point.  */
  };

#ifndef MIPS_DEFAULT_FPU_TYPE
#define MIPS_DEFAULT_FPU_TYPE MIPS_FPU_DOUBLE
#endif
static int mips_fpu_type_auto = 1;
static enum mips_fpu_type mips_fpu_type = MIPS_DEFAULT_FPU_TYPE;
#define MIPS_FPU_TYPE mips_fpu_type

#ifndef MIPS_SAVED_REGSIZE
#define MIPS_SAVED_REGSIZE MIPS_REGSIZE
#endif

/* Do not use "TARGET_IS_MIPS64" to test the size of floating point registers */
#ifndef FP_REGISTER_DOUBLE
#define FP_REGISTER_DOUBLE (REGISTER_VIRTUAL_SIZE(FP0_REGNUM) == 8)
#endif


#define VM_MIN_ADDRESS (CORE_ADDR)0x400000

#if 0
static int mips_in_lenient_prologue PARAMS ((CORE_ADDR, CORE_ADDR));
#endif

int gdb_print_insn_mips PARAMS ((bfd_vma, disassemble_info *));

static void mips_print_register PARAMS ((int, int));

static mips_extra_func_info_t
  heuristic_proc_desc PARAMS ((CORE_ADDR, CORE_ADDR, struct frame_info *));

static CORE_ADDR heuristic_proc_start PARAMS ((CORE_ADDR));

static CORE_ADDR read_next_frame_reg PARAMS ((struct frame_info *, int));

void mips_set_processor_type_command PARAMS ((char *, int));

int mips_set_processor_type PARAMS ((char *));

static void mips_show_processor_type_command PARAMS ((char *, int));

static void reinit_frame_cache_sfunc PARAMS ((char *, int,
                                              struct cmd_list_element *));

static mips_extra_func_info_t
  find_proc_desc PARAMS ((CORE_ADDR pc, struct frame_info * next_frame));

static CORE_ADDR after_prologue PARAMS ((CORE_ADDR pc,
                                         mips_extra_func_info_t proc_desc));

/* This value is the model of MIPS in use.  It is derived from the value
   of the PrID register.  */

char *mips_processor_type;

char *tmp_mips_processor_type;

/* A set of original names, to be used when restoring back to generic
   registers from a specific set.  */

char *mips_generic_reg_names[] = MIPS_REGISTER_NAMES;
char **mips_processor_reg_names = mips_generic_reg_names;

char *
mips_register_name (i)
     int i;
{
  return mips_processor_reg_names[i];
}
/* *INDENT-OFF* */
/* Names of IDT R3041 registers.  */

char *mips_r3041_reg_names[] = {
        "zero", "at",   "v0",   "v1",   "a0",   "a1",   "a2",   "a3",
        "t0",   "t1",   "t2",   "t3",   "t4",   "t5",   "t6",   "t7",
        "s0",   "s1",   "s2",   "s3",   "s4",   "s5",   "s6",   "s7",
        "t8",   "t9",   "k0",   "k1",   "gp",   "sp",   "s8",   "ra",
        "sr",   "lo",   "hi",   "bad",  "cause","pc",
        "f0",   "f1",   "f2",   "f3",   "f4",   "f5",   "f6",   "f7",
        "f8",   "f9",   "f10",  "f11",  "f12",  "f13",  "f14",  "f15",
        "f16",  "f17",  "f18",  "f19",  "f20",  "f21",  "f22",  "f23",
        "f24",  "f25",  "f26",  "f27",  "f28",  "f29",  "f30",  "f31",
        "fsr",  "fir",  "fp",   "",
        "",     "",     "bus",  "ccfg", "",     "",     "",     "",
        "",     "",     "port", "cmp",  "",     "",     "epc",  "prid",
};

/* Names of IDT R3051 registers.  */

char *mips_r3051_reg_names[] = {
        "zero", "at",   "v0",   "v1",   "a0",   "a1",   "a2",   "a3",
        "t0",   "t1",   "t2",   "t3",   "t4",   "t5",   "t6",   "t7",
        "s0",   "s1",   "s2",   "s3",   "s4",   "s5",   "s6",   "s7",
        "t8",   "t9",   "k0",   "k1",   "gp",   "sp",   "s8",   "ra",
        "sr",   "lo",   "hi",   "bad",  "cause","pc",
        "f0",   "f1",   "f2",   "f3",   "f4",   "f5",   "f6",   "f7",
        "f8",   "f9",   "f10",  "f11",  "f12",  "f13",  "f14",  "f15",
        "f16",  "f17",  "f18",  "f19",  "f20",  "f21",  "f22",  "f23",
        "f24",  "f25",  "f26",  "f27",  "f28",  "f29",  "f30",  "f31",
        "fsr",  "fir",  "fp",   "",
        "inx",  "rand", "elo",  "",     "ctxt", "",     "",     "",
        "",     "",     "ehi",  "",     "",     "",     "epc",  "prid",
};

/* Names of IDT R3081 registers.  */

char *mips_r3081_reg_names[] = {
        "zero", "at",   "v0",   "v1",   "a0",   "a1",   "a2",   "a3",
        "t0",   "t1",   "t2",   "t3",   "t4",   "t5",   "t6",   "t7",
        "s0",   "s1",   "s2",   "s3",   "s4",   "s5",   "s6",   "s7",
        "t8",   "t9",   "k0",   "k1",   "gp",   "sp",   "s8",   "ra",
        "sr",   "lo",   "hi",   "bad",  "cause","pc",
        "f0",   "f1",   "f2",   "f3",   "f4",   "f5",   "f6",   "f7",
        "f8",   "f9",   "f10",  "f11",  "f12",  "f13",  "f14",  "f15",
        "f16",  "f17",  "f18",  "f19",  "f20",  "f21",  "f22",  "f23",
        "f24",  "f25",  "f26",  "f27",  "f28",  "f29",  "f30",  "f31",
        "fsr",  "fir",  "fp",   "",
        "inx",  "rand", "elo",  "cfg",  "ctxt", "",     "",     "",
        "",     "",     "ehi",  "",     "",     "",     "epc",  "prid",
};

/* Names of LSI 33k registers.  */

char *mips_lsi33k_reg_names[] = {
        "zero", "at",   "v0",   "v1",   "a0",   "a1",   "a2",   "a3",
        "t0",   "t1",   "t2",   "t3",   "t4",   "t5",   "t6",   "t7",
        "s0",   "s1",   "s2",   "s3",   "s4",   "s5",   "s6",   "s7",
        "t8",   "t9",   "k0",   "k1",   "gp",   "sp",   "s8",   "ra",
        "epc",  "hi",   "lo",   "sr",   "cause","badvaddr",
        "dcic", "bpc",  "bda",  "",     "",     "",     "",      "",
        "",     "",     "",     "",     "",     "",     "",      "",
        "",     "",     "",     "",     "",     "",     "",      "",
        "",     "",     "",     "",     "",     "",     "",      "",
        "",     "",     "",     "",
        "",     "",     "",     "",     "",     "",     "",      "",
        "",     "",     "",     "",     "",     "",     "",      "",
};

struct {
  char *name;
  char **regnames;
} mips_processor_type_table[] = {
  { "generic", mips_generic_reg_names },
  { "r3041", mips_r3041_reg_names },
  { "r3051", mips_r3051_reg_names },
  { "r3071", mips_r3081_reg_names },
  { "r3081", mips_r3081_reg_names },
  { "lsi33k", mips_lsi33k_reg_names },
  { NULL, NULL }
};
/* *INDENT-ON* */




/* Table to translate MIPS16 register field to actual register number.  */
static int mips16_to_32_reg[8] =
{16, 17, 2, 3, 4, 5, 6, 7};

/* Heuristic_proc_start may hunt through the text section for a long
   time across a 2400 baud serial line.  Allows the user to limit this
   search.  */

static unsigned int heuristic_fence_post = 0;

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

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

void
mips_print_extra_frame_info (fi)
     struct frame_info *fi;
{
  if (fi
      && fi->extra_info
      && fi->extra_info->proc_desc
      && fi->extra_info->proc_desc->pdr.framereg < NUM_REGS)
    printf_filtered (" frame pointer is at %s+%d\n",
                     REGISTER_NAME (fi->extra_info->proc_desc->pdr.framereg),
                     fi->extra_info->proc_desc->pdr.frameoffset);
}

/* Convert between RAW and VIRTUAL registers.  The RAW register size
   defines the remote-gdb packet. */

static int mips64_transfers_32bit_regs_p = 0;

int
mips_register_raw_size (reg_nr)
     int reg_nr;
{
  if (mips64_transfers_32bit_regs_p)
    return REGISTER_VIRTUAL_SIZE (reg_nr);
  else
    return MIPS_REGSIZE;
}

int
mips_register_convertible (reg_nr)
     int reg_nr;
{
  if (mips64_transfers_32bit_regs_p)
    return 0;
  else
    return (REGISTER_RAW_SIZE (reg_nr) > REGISTER_VIRTUAL_SIZE (reg_nr));
}

void
mips_register_convert_to_virtual (n, virtual_type, raw_buf, virt_buf)
     int n;
     struct type *virtual_type;
     char *raw_buf;
     char *virt_buf;
{
  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    memcpy (virt_buf,
            raw_buf + (REGISTER_RAW_SIZE (n) - TYPE_LENGTH (virtual_type)),
            TYPE_LENGTH (virtual_type));
  else
    memcpy (virt_buf,
            raw_buf,
            TYPE_LENGTH (virtual_type));
}

void
mips_register_convert_to_raw (virtual_type, n, virt_buf, raw_buf)
     struct type *virtual_type;
     int n;
     char *virt_buf;
     char *raw_buf;
{
  memset (raw_buf, 0, REGISTER_RAW_SIZE (n));
  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    memcpy (raw_buf + (REGISTER_RAW_SIZE (n) - TYPE_LENGTH (virtual_type)),
            virt_buf,
            TYPE_LENGTH (virtual_type));
  else
    memcpy (raw_buf,
            virt_buf,
            TYPE_LENGTH (virtual_type));
}

/* Should the upper word of 64-bit addresses be zeroed? */
static int mask_address_p = 1;

/* Should call_function allocate stack space for a struct return?  */
int
mips_use_struct_convention (gcc_p, type)
     int gcc_p;
     struct type *type;
{
  if (MIPS_EABI)
    return (TYPE_LENGTH (type) > 2 * MIPS_SAVED_REGSIZE);
  else
    return 1;                   /* Structures are returned by ref in extra arg0 */
}

/* Tell if the program counter value in MEMADDR is in a MIPS16 function.  */

static int
pc_is_mips16 (bfd_vma memaddr)
{
  struct minimal_symbol *sym;

  /* If bit 0 of the address is set, assume this is a MIPS16 address. */
  if (IS_MIPS16_ADDR (memaddr))
    return 1;

  /* A flag indicating that this is a MIPS16 function is stored by elfread.c in
     the high bit of the info field.  Use this to decide if the function is
     MIPS16 or normal MIPS.  */
  sym = lookup_minimal_symbol_by_pc (memaddr);
  if (sym)
    return MSYMBOL_IS_SPECIAL (sym);
  else
    return 0;
}


/* This returns the PC of the first inst after the prologue.  If we can't
   find the prologue, then return 0.  */

static CORE_ADDR
after_prologue (pc, proc_desc)
     CORE_ADDR pc;
     mips_extra_func_info_t proc_desc;
{
  struct symtab_and_line sal;
  CORE_ADDR func_addr, func_end;

  if (!proc_desc)
    proc_desc = find_proc_desc (pc, NULL);

  if (proc_desc)
    {
      /* If function is frameless, then we need to do it the hard way.  I
         strongly suspect that frameless always means prologueless... */
      if (PROC_FRAME_REG (proc_desc) == SP_REGNUM
          && PROC_FRAME_OFFSET (proc_desc) == 0)
        return 0;
    }

  if (!find_pc_partial_function (pc, NULL, &func_addr, &func_end))
    return 0;                   /* Unknown */

  sal = find_pc_line (func_addr, 0);

  if (sal.end < func_end)
    return sal.end;

  /* The line after the prologue is after the end of the function.  In this
     case, tell the caller to find the prologue the hard way.  */

  return 0;
}

/* Decode a MIPS32 instruction that saves a register in the stack, and
   set the appropriate bit in the general register mask or float register mask
   to indicate which register is saved.  This is a helper function
   for mips_find_saved_regs.  */

static void
mips32_decode_reg_save (inst, gen_mask, float_mask)
     t_inst inst;
     unsigned long *gen_mask;
     unsigned long *float_mask;
{
  int reg;

  if ((inst & 0xffe00000) == 0xafa00000         /* sw reg,n($sp) */
      || (inst & 0xffe00000) == 0xafc00000      /* sw reg,n($r30) */
      || (inst & 0xffe00000) == 0xffa00000)     /* sd reg,n($sp) */
    {
      /* It might be possible to use the instruction to
         find the offset, rather than the code below which
         is based on things being in a certain order in the
         frame, but figuring out what the instruction's offset
         is relative to might be a little tricky.  */
      reg = (inst & 0x001f0000) >> 16;
      *gen_mask |= (1 << reg);
    }
  else if ((inst & 0xffe00000) == 0xe7a00000    /* swc1 freg,n($sp) */
           || (inst & 0xffe00000) == 0xe7c00000         /* swc1 freg,n($r30) */
           || (inst & 0xffe00000) == 0xf7a00000)        /* sdc1 freg,n($sp) */

    {
      reg = ((inst & 0x001f0000) >> 16);
      *float_mask |= (1 << reg);
    }
}

/* Decode a MIPS16 instruction that saves a register in the stack, and
   set the appropriate bit in the general register or float register mask
   to indicate which register is saved.  This is a helper function
   for mips_find_saved_regs.  */

static void
mips16_decode_reg_save (inst, gen_mask)
     t_inst inst;
     unsigned long *gen_mask;
{
  if ((inst & 0xf800) == 0xd000)        /* sw reg,n($sp) */
    {
      int reg = mips16_to_32_reg[(inst & 0x700) >> 8];
      *gen_mask |= (1 << reg);
    }
  else if ((inst & 0xff00) == 0xf900)   /* sd reg,n($sp) */
    {
      int reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
      *gen_mask |= (1 << reg);
    }
  else if ((inst & 0xff00) == 0x6200    /* sw $ra,n($sp) */
           || (inst & 0xff00) == 0xfa00)        /* sd $ra,n($sp) */
    *gen_mask |= (1 << RA_REGNUM);
}


/* Fetch and return instruction from the specified location.  If the PC
   is odd, assume it's a MIPS16 instruction; otherwise MIPS32.  */

static t_inst
mips_fetch_instruction (addr)
     CORE_ADDR addr;
{
  char buf[MIPS_INSTLEN];
  int instlen;
  int status;

  if (pc_is_mips16 (addr))
    {
      instlen = MIPS16_INSTLEN;
      addr = UNMAKE_MIPS16_ADDR (addr);
    }
  else
    instlen = MIPS_INSTLEN;
  status = read_memory_nobpt (addr, buf, instlen);
  if (status)
    memory_error (status, addr);
  return extract_unsigned_integer (buf, instlen);
}


/* These the fields of 32 bit mips instructions */
#define mips32_op(x) (x >> 25)
#define itype_op(x) (x >> 25)
#define itype_rs(x) ((x >> 21)& 0x1f)
#define itype_rt(x) ((x >> 16) & 0x1f)
#define itype_immediate(x) ( x & 0xffff)

#define jtype_op(x) (x >> 25)
#define jtype_target(x) ( x & 0x03fffff)

#define rtype_op(x) (x >>25)
#define rtype_rs(x) ((x>>21) & 0x1f)
#define rtype_rt(x) ((x>>16)  & 0x1f)
#define rtype_rd(x) ((x>>11) & 0x1f)
#define rtype_shamt(x) ((x>>6) & 0x1f)
#define rtype_funct(x) (x & 0x3f )

static CORE_ADDR
mips32_relative_offset (unsigned long inst)
{
  long x;
  x = itype_immediate (inst);
  if (x & 0x8000)               /* sign bit set */
    {
      x |= 0xffff0000;          /* sign extension */
    }
  x = x << 2;
  return x;
}

/* Determine whate to set a single step breakpoint while considering
   branch prediction */
CORE_ADDR
mips32_next_pc (CORE_ADDR pc)
{
  unsigned long inst;
  int op;
  inst = mips_fetch_instruction (pc);
  if ((inst & 0xe0000000) != 0) /* Not a special, junp or branch instruction */
    {
      if ((inst >> 27) == 5)    /* BEQL BNEZ BLEZL BGTZE , bits 0101xx */
        {
          op = ((inst >> 25) & 0x03);
          switch (op)
            {
            case 0:
              goto equal_branch;        /* BEQL   */
            case 1:
              goto neq_branch;  /* BNEZ   */
            case 2:
              goto less_branch; /* BLEZ   */
            case 3:
              goto greater_branch;      /* BGTZ */
            default:
              pc += 4;
            }
        }
      else
        pc += 4;                /* Not a branch, next instruction is easy */
    }
  else
    {                           /* This gets way messy */

      /* Further subdivide into SPECIAL, REGIMM and other */
      switch (op = ((inst >> 26) & 0x07))       /* extract bits 28,27,26 */
        {
        case 0:         /* SPECIAL */
          op = rtype_funct (inst);
          switch (op)
            {
            case 8:             /* JR */
            case 9:             /* JALR */
              pc = read_register (rtype_rs (inst));     /* Set PC to that address */
              break;
            default:
              pc += 4;
            }

          break;                /* end special */
        case 1:         /* REGIMM */
          {
            op = jtype_op (inst);       /* branch condition */
            switch (jtype_op (inst))
              {
              case 0:           /* BLTZ */
              case 2:           /* BLTXL */
              case 16:          /* BLTZALL */
              case 18:          /* BLTZALL */
              less_branch:
                if (read_register (itype_rs (inst)) < 0)
                  pc += mips32_relative_offset (inst) + 4;
                else
                  pc += 8;      /* after the delay slot */
                break;
              case 1:           /* GEZ */
              case 3:           /* BGEZL */
              case 17:          /* BGEZAL */
              case 19:          /* BGEZALL */
              greater_equal_branch:
                if (read_register (itype_rs (inst)) >= 0)
                  pc += mips32_relative_offset (inst) + 4;
                else
                  pc += 8;      /* after the delay slot */
                break;
                /* All of the other intructions in the REGIMM catagory */
              default:
                pc += 4;
              }
          }
          break;                /* end REGIMM */
        case 2:         /* J */
        case 3:         /* JAL */
          {
            unsigned long reg;
            reg = jtype_target (inst) << 2;
            pc = reg + ((pc + 4) & 0xf0000000);
            /* Whats this mysterious 0xf000000 adjustment ??? */
          }
          break;
          /* FIXME case JALX : */
          {
            unsigned long reg;
            reg = jtype_target (inst) << 2;
            pc = reg + ((pc + 4) & 0xf0000000) + 1;     /* yes, +1 */
            /* Add 1 to indicate 16 bit mode - Invert ISA mode */
          }
          break;                /* The new PC will be alternate mode */
        case 4:         /* BEQ , BEQL */
        equal_branch:
          if (read_register (itype_rs (inst)) ==
              read_register (itype_rt (inst)))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 5:         /* BNE , BNEL */
        neq_branch:
          if (read_register (itype_rs (inst)) !=
              read_register (itype_rs (inst)))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 6:         /* BLEZ , BLEZL */
        less_zero_branch:
          if (read_register (itype_rs (inst) <= 0))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 7:
        greater_branch: /* BGTZ BGTZL */
          if (read_register (itype_rs (inst) > 0))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        default:
          pc += 8;
        }                       /* switch */
    }                           /* else */
  return pc;
}                               /* mips32_next_pc */

/* Decoding the next place to set a breakpoint is irregular for the
   mips 16 variant, but fortunatly, there fewer instructions. We have to cope
   ith extensions for 16 bit instructions and a pair of actual 32 bit instructions.
   We dont want to set a single step instruction on the extend instruction
   either.
 */

/* Lots of mips16 instruction formats */
/* Predicting jumps requires itype,ritype,i8type
   and their extensions      extItype,extritype,extI8type
 */
enum mips16_inst_fmts
{
  itype,                        /* 0  immediate 5,10 */
  ritype,                       /* 1   5,3,8 */
  rrtype,                       /* 2   5,3,3,5 */
  rritype,                      /* 3   5,3,3,5 */
  rrrtype,                      /* 4   5,3,3,3,2 */
  rriatype,                     /* 5   5,3,3,1,4 */
  shifttype,                    /* 6   5,3,3,3,2 */
  i8type,                       /* 7   5,3,8 */
  i8movtype,                    /* 8   5,3,3,5 */
  i8mov32rtype,                 /* 9   5,3,5,3 */
  i64type,                      /* 10  5,3,8 */
  ri64type,                     /* 11  5,3,3,5 */
  jalxtype,                     /* 12  5,1,5,5,16 - a 32 bit instruction */
  exiItype,                     /* 13  5,6,5,5,1,1,1,1,1,1,5 */
  extRitype,                    /* 14  5,6,5,5,3,1,1,1,5 */
  extRRItype,                   /* 15  5,5,5,5,3,3,5 */
  extRRIAtype,                  /* 16  5,7,4,5,3,3,1,4 */
  EXTshifttype,                 /* 17  5,5,1,1,1,1,1,1,5,3,3,1,1,1,2 */
  extI8type,                    /* 18  5,6,5,5,3,1,1,1,5 */
  extI64type,                   /* 19  5,6,5,5,3,1,1,1,5 */
  extRi64type,                  /* 20  5,6,5,5,3,3,5 */
  extshift64type                /* 21  5,5,1,1,1,1,1,1,5,1,1,1,3,5 */
};
/* I am heaping all the fields of the formats into one structure and then,
   only the fields which are involved in instruction extension */
struct upk_mips16
  {
    unsigned short inst;
    enum mips16_inst_fmts fmt;
    unsigned long offset;
    unsigned int regx;          /* Function in i8 type */
    unsigned int regy;
  };



static void
print_unpack (char *comment,
              struct upk_mips16 *u)
{
  printf ("%s %04x ,f(%d) off(%08x) (x(%x) y(%x)\n",
          comment, u->inst, u->fmt, u->offset, u->regx, u->regy);
}

/* The EXT-I, EXT-ri nad EXT-I8 instructions all have the same
   format for the bits which make up the immediatate extension.
 */
static unsigned long
extended_offset (unsigned long extension)
{
  unsigned long value;
  value = (extension >> 21) & 0x3f;     /* * extract 15:11 */
  value = value << 6;
  value |= (extension >> 16) & 0x1f;    /* extrace 10:5 */
  value = value << 5;
  value |= extension & 0x01f;   /* extract 4:0 */
  return value;
}

/* Only call this function if you know that this is an extendable
   instruction, It wont malfunction, but why make excess remote memory references?
   If the immediate operands get sign extended or somthing, do it after
   the extension is performed.
 */
/* FIXME: Every one of these cases needs to worry about sign extension
   when the offset is to be used in relative addressing */


static unsigned short
fetch_mips_16 (CORE_ADDR pc)
{
  char buf[8];
  pc &= 0xfffffffe;             /* clear the low order bit */
  target_read_memory (pc, buf, 2);
  return extract_unsigned_integer (buf, 2);
}

static void
unpack_mips16 (CORE_ADDR pc,
               struct upk_mips16 *upk)
{
  CORE_ADDR extpc;
  unsigned long extension;
  int extended;
  extpc = (pc - 4) & ~0x01;     /* Extensions are 32 bit instructions */
  /* Decrement to previous address and loose the 16bit mode flag */
  /* return if the instruction was extendable, but not actually extended */
  extended = ((mips32_op (extension) == 30) ? 1 : 0);
  if (extended)
    {
      extension = mips_fetch_instruction (extpc);
    }
  switch (upk->fmt)
    {
    case itype:
      {
        unsigned long value;
        if (extended)
          {
            value = extended_offset (extension);
            value = value << 11;        /* rom for the original value */
            value |= upk->inst & 0x7ff;         /* eleven bits from instruction */
          }
        else
          {
            value = upk->inst & 0x7ff;
            /* FIXME : Consider sign extension */
          }
        upk->offset = value;
      }
      break;
    case ritype:
    case i8type:
      {                         /* A register identifier and an offset */
        /* Most of the fields are the same as I type but the
           immediate value is of a different length */
        unsigned long value;
        if (extended)
          {
            value = extended_offset (extension);
            value = value << 8; /* from the original instruction */
            value |= upk->inst & 0xff;  /* eleven bits from instruction */
            upk->regx = (extension >> 8) & 0x07;        /* or i8 funct */
            if (value & 0x4000) /* test the sign bit , bit 26 */
              {
                value &= ~0x3fff;       /* remove the sign bit */
                value = -value;
              }
          }
        else
          {
            value = upk->inst & 0xff;   /* 8 bits */
            upk->regx = (upk->inst >> 8) & 0x07;        /* or i8 funct */
            /* FIXME: Do sign extension , this format needs it */
            if (value & 0x80)   /* THIS CONFUSES ME */
              {
                value &= 0xef;  /* remove the sign bit */
                value = -value;
              }

          }
        upk->offset = value;
        break;
      }
    case jalxtype:
      {
        unsigned long value;
        unsigned short nexthalf;
        value = ((upk->inst & 0x1f) << 5) | ((upk->inst >> 5) & 0x1f);
        value = value << 16;
        nexthalf = mips_fetch_instruction (pc + 2);     /* low bit still set */
        value |= nexthalf;
        upk->offset = value;
        break;
      }
    default:
      printf_filtered ("Decoding unimplemented instruction format type\n");
      break;
    }
  /* print_unpack("UPK",upk) ; */
}


#define mips16_op(x) (x >> 11)

/* This is a map of the opcodes which ae known to perform branches */
static unsigned char map16[32] =
{0, 0, 1, 1, 1, 1, 0, 0,
 0, 0, 0, 0, 1, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 1, 1, 0
};

static CORE_ADDR
add_offset_16 (CORE_ADDR pc, int offset)
{
  return ((offset << 2) | ((pc + 2) & (0xf0000000)));

}



static struct upk_mips16 upk;

CORE_ADDR
mips16_next_pc (CORE_ADDR pc)
{
  int op;
  t_inst inst;
  /* inst = mips_fetch_instruction(pc) ; - This doesnt always work */
  inst = fetch_mips_16 (pc);
  upk.inst = inst;
  op = mips16_op (upk.inst);
  if (map16[op])
    {
      int reg;
      switch (op)
        {
        case 2:         /* Branch */
          upk.fmt = itype;
          unpack_mips16 (pc, &upk);
          {
            long offset;
            offset = upk.offset;
            if (offset & 0x800)
              {
                offset &= 0xeff;
                offset = -offset;
              }
            pc += (offset << 1) + 2;
          }
          break;
        case 3:         /* JAL , JALX - Watch out, these are 32 bit instruction */
          upk.fmt = jalxtype;
          unpack_mips16 (pc, &upk);
          pc = add_offset_16 (pc, upk.offset);
          if ((upk.inst >> 10) & 0x01)  /* Exchange mode */
            pc = pc & ~0x01;    /* Clear low bit, indicate 32 bit mode */
          else
            pc |= 0x01;
          break;
        case 4:         /* beqz */
          upk.fmt = ritype;
          unpack_mips16 (pc, &upk);
          reg = read_register (upk.regx);
          if (reg == 0)
            pc += (upk.offset << 1) + 2;
          else
            pc += 2;
          break;
        case 5:         /* bnez */
          upk.fmt = ritype;
          unpack_mips16 (pc, &upk);
          reg = read_register (upk.regx);
          if (reg != 0)
            pc += (upk.offset << 1) + 2;
          else
            pc += 2;
          break;
        case 12:                /* I8 Formats btez btnez */
          upk.fmt = i8type;
          unpack_mips16 (pc, &upk);
          /* upk.regx contains the opcode */
          reg = read_register (24);     /* Test register is 24 */
          if (((upk.regx == 0) && (reg == 0))   /* BTEZ */
              || ((upk.regx == 1) && (reg != 0)))       /* BTNEZ */
            /* pc = add_offset_16(pc,upk.offset) ; */
            pc += (upk.offset << 1) + 2;
          else
            pc += 2;
          break;
        case 29:                /* RR Formats JR, JALR, JALR-RA */
          upk.fmt = rrtype;
          op = upk.inst & 0x1f;
          if (op == 0)
            {
              upk.regx = (upk.inst >> 8) & 0x07;
              upk.regy = (upk.inst >> 5) & 0x07;
              switch (upk.regy)
                {
                case 0:
                  reg = upk.regx;
                  break;
                case 1:
                  reg = 31;
                  break;        /* Function return instruction */
                case 2:
                  reg = upk.regx;
                  break;
                default:
                  reg = 31;
                  break;        /* BOGUS Guess */
                }
              pc = read_register (reg);
            }
          else
            pc += 2;
          break;
        case 30:                /* This is an extend instruction */
          pc += 4;              /* Dont be setting breakpints on the second half */
          break;
        default:
          printf ("Filtered - next PC probably incorrrect due to jump inst\n");
          pc += 2;
          break;
        }
    }
  else
    pc += 2;                    /* just a good old instruction */
  /* See if we CAN actually break on the next instruction */
  /* printf("NXTm16PC %08x\n",(unsigned long)pc) ; */
  return pc;
}                               /* mips16_next_pc */

/* The mips_next_pc function supports single_tep when the remote target monitor or
   stub is not developed enough to so a single_step.
   It works by decoding the current instruction and predicting where a branch
   will go. This isnt hard because all the data is available.
   The MIPS32 and MIPS16 variants are quite different
 */
CORE_ADDR
mips_next_pc (CORE_ADDR pc)
{
  t_inst inst;
  /* inst = mips_fetch_instruction(pc) ; */
  /* if (pc_is_mips16) <----- This is failing */
  if (pc & 0x01)
    return mips16_next_pc (pc);
  else
    return mips32_next_pc (pc);
}                               /* mips_next_pc */

/* Guaranteed to set fci->saved_regs to some values (it never leaves it
   NULL).  */

void
mips_find_saved_regs (fci)
     struct frame_info *fci;
{
  int ireg;
  CORE_ADDR reg_position;
  /* r0 bit means kernel trap */
  int kernel_trap;
  /* What registers have been saved?  Bitmasks.  */
  unsigned long gen_mask, float_mask;
  mips_extra_func_info_t proc_desc;
  t_inst inst;

  frame_saved_regs_zalloc (fci);

  /* If it is the frame for sigtramp, the saved registers are located
     in a sigcontext structure somewhere on the stack.
     If the stack layout for sigtramp changes we might have to change these
     constants and the companion fixup_sigtramp in mdebugread.c  */
#ifndef SIGFRAME_BASE
/* To satisfy alignment restrictions, sigcontext is located 4 bytes
   above the sigtramp frame.  */
#define SIGFRAME_BASE           MIPS_REGSIZE
/* FIXME!  Are these correct?? */
#define SIGFRAME_PC_OFF         (SIGFRAME_BASE + 2 * MIPS_REGSIZE)
#define SIGFRAME_REGSAVE_OFF    (SIGFRAME_BASE + 3 * MIPS_REGSIZE)
#define SIGFRAME_FPREGSAVE_OFF  \
        (SIGFRAME_REGSAVE_OFF + MIPS_NUMREGS * MIPS_REGSIZE + 3 * MIPS_REGSIZE)
#endif
#ifndef SIGFRAME_REG_SIZE
/* FIXME!  Is this correct?? */
#define SIGFRAME_REG_SIZE       MIPS_REGSIZE
#endif
  if (fci->signal_handler_caller)
    {
      for (ireg = 0; ireg < MIPS_NUMREGS; ireg++)
        {
          reg_position = fci->frame + SIGFRAME_REGSAVE_OFF
            + ireg * SIGFRAME_REG_SIZE;
          fci->saved_regs[ireg] = reg_position;
        }
      for (ireg = 0; ireg < MIPS_NUMREGS; ireg++)
        {
          reg_position = fci->frame + SIGFRAME_FPREGSAVE_OFF
            + ireg * SIGFRAME_REG_SIZE;
          fci->saved_regs[FP0_REGNUM + ireg] = reg_position;
        }
      fci->saved_regs[PC_REGNUM] = fci->frame + SIGFRAME_PC_OFF;
      return;
    }

  proc_desc = fci->extra_info->proc_desc;
  if (proc_desc == NULL)
    /* I'm not sure how/whether this can happen.  Normally when we can't
       find a proc_desc, we "synthesize" one using heuristic_proc_desc
       and set the saved_regs right away.  */
    return;

  kernel_trap = PROC_REG_MASK (proc_desc) & 1;
  gen_mask = kernel_trap ? 0xFFFFFFFF : PROC_REG_MASK (proc_desc);
  float_mask = kernel_trap ? 0xFFFFFFFF : PROC_FREG_MASK (proc_desc);

  if (                          /* In any frame other than the innermost or a frame interrupted by
                                   a signal, we assume that all registers have been saved.
                                   This assumes that all register saves in a function happen before
                                   the first function call.  */
       (fci->next == NULL || fci->next->signal_handler_caller)

  /* In a dummy frame we know exactly where things are saved.  */
       && !PROC_DESC_IS_DUMMY (proc_desc)

  /* Don't bother unless we are inside a function prologue.  Outside the
     prologue, we know where everything is. */

       && in_prologue (fci->pc, PROC_LOW_ADDR (proc_desc))

  /* Not sure exactly what kernel_trap means, but if it means
     the kernel saves the registers without a prologue doing it,
     we better not examine the prologue to see whether registers
     have been saved yet.  */
       && !kernel_trap)
    {
      /* We need to figure out whether the registers that the proc_desc
         claims are saved have been saved yet.  */

      CORE_ADDR addr;

      /* Bitmasks; set if we have found a save for the register.  */
      unsigned long gen_save_found = 0;
      unsigned long float_save_found = 0;
      int instlen;

      /* If the address is odd, assume this is MIPS16 code.  */
      addr = PROC_LOW_ADDR (proc_desc);
      instlen = pc_is_mips16 (addr) ? MIPS16_INSTLEN : MIPS_INSTLEN;

      /* Scan through this function's instructions preceding the current
         PC, and look for those that save registers.  */
      while (addr < fci->pc)
        {
          inst = mips_fetch_instruction (addr);
          if (pc_is_mips16 (addr))
            mips16_decode_reg_save (inst, &gen_save_found);
          else
            mips32_decode_reg_save (inst, &gen_save_found, &float_save_found);
          addr += instlen;
        }
      gen_mask = gen_save_found;
      float_mask = float_save_found;
    }

  /* Fill in the offsets for the registers which gen_mask says
     were saved.  */
  reg_position = fci->frame + PROC_REG_OFFSET (proc_desc);
  for (ireg = MIPS_NUMREGS - 1; gen_mask; --ireg, gen_mask <<= 1)
    if (gen_mask & 0x80000000)
      {
        fci->saved_regs[ireg] = reg_position;
        reg_position -= MIPS_SAVED_REGSIZE;
      }

  /* The MIPS16 entry instruction saves $s0 and $s1 in the reverse order
     of that normally used by gcc.  Therefore, we have to fetch the first
     instruction of the function, and if it's an entry instruction that
     saves $s0 or $s1, correct their saved addresses.  */
  if (pc_is_mips16 (PROC_LOW_ADDR (proc_desc)))
    {
      inst = mips_fetch_instruction (PROC_LOW_ADDR (proc_desc));
      if ((inst & 0xf81f) == 0xe809 && (inst & 0x700) != 0x700)         /* entry */
        {
          int reg;
          int sreg_count = (inst >> 6) & 3;

          /* Check if the ra register was pushed on the stack.  */
          reg_position = fci->frame + PROC_REG_OFFSET (proc_desc);
          if (inst & 0x20)
            reg_position -= MIPS_SAVED_REGSIZE;

          /* Check if the s0 and s1 registers were pushed on the stack.  */
          for (reg = 16; reg < sreg_count + 16; reg++)
            {
              fci->saved_regs[reg] = reg_position;
              reg_position -= MIPS_SAVED_REGSIZE;
            }
        }
    }

  /* Fill in the offsets for the registers which float_mask says
     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. */
  if (!GDB_TARGET_IS_MIPS64)
    reg_position += MIPS_SAVED_REGSIZE;

  /* Fill in the offsets for the float registers which float_mask says
     were saved.  */
  for (ireg = MIPS_NUMREGS - 1; float_mask; --ireg, float_mask <<= 1)
    if (float_mask & 0x80000000)
      {
        fci->saved_regs[FP0_REGNUM + ireg] = reg_position;
        reg_position -= MIPS_SAVED_REGSIZE;
      }

  fci->saved_regs[PC_REGNUM] = fci->saved_regs[RA_REGNUM];
}

static CORE_ADDR
read_next_frame_reg (fi, regno)
     struct frame_info *fi;
     int regno;
{
  for (; fi; fi = fi->next)
    {
      /* We have to get the saved sp from the sigcontext
         if it is a signal handler frame.  */
      if (regno == SP_REGNUM && !fi->signal_handler_caller)
        return fi->frame;
      else
        {
          if (fi->saved_regs == NULL)
            mips_find_saved_regs (fi);
          if (fi->saved_regs[regno])
            return read_memory_integer (fi->saved_regs[regno], MIPS_SAVED_REGSIZE);
        }
    }
  return read_register (regno);
}

/* mips_addr_bits_remove - remove useless address bits  */

CORE_ADDR
mips_addr_bits_remove (addr)
     CORE_ADDR addr;
{
#if GDB_TARGET_IS_MIPS64
  if (mask_address_p && (addr >> 32 == (CORE_ADDR) 0xffffffff))
    {
      /* This hack is a work-around for existing boards using PMON,
         the simulator, and any other 64-bit targets that doesn't have
         true 64-bit addressing.  On these targets, the upper 32 bits
         of addresses are ignored by the hardware.  Thus, the PC or SP
         are likely to have been sign extended to all 1s by instruction
         sequences that load 32-bit addresses.  For example, a typical
         piece of code that loads an address is this:
         lui $r2, <upper 16 bits>
         ori $r2, <lower 16 bits>
         But the lui sign-extends the value such that the upper 32 bits
         may be all 1s.  The workaround is simply to mask off these bits.
         In the future, gcc may be changed to support true 64-bit
         addressing, and this masking will have to be disabled.  */
      addr &= (CORE_ADDR) 0xffffffff;
    }
#else
  /* Even when GDB is configured for some 32-bit targets (e.g. mips-elf),
     BFD is configured to handle 64-bit targets, so CORE_ADDR is 64 bits.
     So we still have to mask off useless bits from addresses.  */
  addr &= (CORE_ADDR) 0xffffffff;
#endif

  return addr;
}

void
mips_init_frame_pc_first (fromleaf, prev)
     int fromleaf;
     struct frame_info *prev;
{
  CORE_ADDR pc, tmp;

  pc = ((fromleaf) ? SAVED_PC_AFTER_CALL (prev->next) :
        prev->next ? FRAME_SAVED_PC (prev->next) : read_pc ());
  tmp = mips_skip_stub (pc);
  prev->pc = tmp ? tmp : pc;
}


CORE_ADDR
mips_frame_saved_pc (frame)
     struct frame_info *frame;
{
  CORE_ADDR saved_pc;
  mips_extra_func_info_t proc_desc = frame->extra_info->proc_desc;
  /* We have to get the saved pc from the sigcontext
     if it is a signal handler frame.  */
  int pcreg = frame->signal_handler_caller ? PC_REGNUM
  : (proc_desc ? PROC_PC_REG (proc_desc) : RA_REGNUM);

  if (proc_desc && PROC_DESC_IS_DUMMY (proc_desc))
    saved_pc = read_memory_integer (frame->frame - MIPS_SAVED_REGSIZE, MIPS_SAVED_REGSIZE);
  else
    saved_pc = read_next_frame_reg (frame, pcreg);

  return ADDR_BITS_REMOVE (saved_pc);
}

static struct mips_extra_func_info temp_proc_desc;
static CORE_ADDR temp_saved_regs[NUM_REGS];

/* Set a register's saved stack address in temp_saved_regs.  If an address
   has already been set for this register, do nothing; this way we will
   only recognize the first save of a given register in a function prologue.
   This is a helper function for mips{16,32}_heuristic_proc_desc.  */

static void
set_reg_offset (regno, offset)
     int regno;
     CORE_ADDR offset;
{
  if (temp_saved_regs[regno] == 0)
    temp_saved_regs[regno] = offset;
}


/* Test whether the PC points to the return instruction at the
   end of a function. */

static int
mips_about_to_return (pc)
     CORE_ADDR pc;
{
  if (pc_is_mips16 (pc))
    /* This mips16 case isn't necessarily reliable.  Sometimes the compiler
       generates a "jr $ra"; other times it generates code to load
       the return address from the stack to an accessible register (such
       as $a3), then a "jr" using that register.  This second case
       is almost impossible to distinguish from an indirect jump
       used for switch statements, so we don't even try.  */
    return mips_fetch_instruction (pc) == 0xe820;       /* jr $ra */
  else
    return mips_fetch_instruction (pc) == 0x3e00008;    /* jr $ra */
}


/* This fencepost looks highly suspicious to me.  Removing it also
   seems suspicious as it could affect remote debugging across serial
   lines.  */

static CORE_ADDR
heuristic_proc_start (pc)
     CORE_ADDR pc;
{
  CORE_ADDR start_pc;
  CORE_ADDR fence;
  int instlen;
  int seen_adjsp = 0;

  pc = ADDR_BITS_REMOVE (pc);
  start_pc = pc;
  fence = start_pc - heuristic_fence_post;
  if (start_pc == 0)
    return 0;

  if (heuristic_fence_post == UINT_MAX
      || fence < VM_MIN_ADDRESS)
    fence = VM_MIN_ADDRESS;

  instlen = pc_is_mips16 (pc) ? MIPS16_INSTLEN : MIPS_INSTLEN;

  /* search back for previous return */
  for (start_pc -= instlen;; start_pc -= instlen)
    if (start_pc < fence)
      {
        /* It's not clear to me why we reach this point when
           stop_soon_quietly, but with this test, at least we
           don't print out warnings for every child forked (eg, on
           decstation).  22apr93 rich@cygnus.com.  */
        if (!stop_soon_quietly)
          {
            static int blurb_printed = 0;

            warning ("Warning: GDB can't find the start of the function at 0x%s.",
                     paddr_nz (pc));

            if (!blurb_printed)
              {
                /* This actually happens frequently in embedded
                   development, when you first connect to a board
                   and your stack pointer and pc are nowhere in
                   particular.  This message needs to give people
                   in that situation enough information to
                   determine that it's no big deal.  */
                printf_filtered ("\n\
    GDB is unable to find the start of the function at 0x%s\n\
and thus can't determine the size of that function's stack frame.\n\
This means that GDB may be unable to access that stack frame, or\n\
the frames below it.\n\
    This problem is most likely caused by an invalid program counter or\n\
stack pointer.\n\
    However, if you think GDB should simply search farther back\n\
from 0x%s for code which looks like the beginning of a\n\
function, you can increase the range of the search using the `set\n\
heuristic-fence-post' command.\n",
                                 paddr_nz (pc), paddr_nz (pc));
                blurb_printed = 1;
              }
          }

        return 0;
      }
    else if (pc_is_mips16 (start_pc))
      {
        unsigned short inst;

        /* On MIPS16, any one of the following is likely to be the
           start of a function:
           entry
           addiu sp,-n
           daddiu sp,-n
           extend -n followed by 'addiu sp,+n' or 'daddiu sp,+n'  */
        inst = mips_fetch_instruction (start_pc);
        if (((inst & 0xf81f) == 0xe809 && (inst & 0x700) != 0x700)      /* entry */
            || (inst & 0xff80) == 0x6380        /* addiu sp,-n */
            || (inst & 0xff80) == 0xfb80        /* daddiu sp,-n */
            || ((inst & 0xf810) == 0xf010 && seen_adjsp))       /* extend -n */
          break;
        else if ((inst & 0xff00) == 0x6300      /* addiu sp */
                 || (inst & 0xff00) == 0xfb00)  /* daddiu sp */
          seen_adjsp = 1;
        else
          seen_adjsp = 0;
      }
    else if (mips_about_to_return (start_pc))
      {
        start_pc += 2 * MIPS_INSTLEN;   /* skip return, and its delay slot */
        break;
      }

#if 0
  /* skip nops (usually 1) 0 - is this */
  while (start_pc < pc && read_memory_integer (start_pc, MIPS_INSTLEN) == 0)
    start_pc += MIPS_INSTLEN;
#endif
  return start_pc;
}

/* Fetch the immediate value from a MIPS16 instruction.
   If the previous instruction was an EXTEND, use it to extend
   the upper bits of the immediate value.  This is a helper function
   for mips16_heuristic_proc_desc.  */

static int
mips16_get_imm (prev_inst, inst, nbits, scale, is_signed)
     unsigned short prev_inst;  /* previous instruction */
     unsigned short inst;       /* current instruction */
     int nbits;                 /* number of bits in imm field */
     int scale;                 /* scale factor to be applied to imm */
     int is_signed;             /* is the imm field signed? */
{
  int offset;

  if ((prev_inst & 0xf800) == 0xf000)   /* prev instruction was EXTEND? */
    {
      offset = ((prev_inst & 0x1f) << 11) | (prev_inst & 0x7e0);
      if (offset & 0x8000)      /* check for negative extend */
        offset = 0 - (0x10000 - (offset & 0xffff));
      return offset | (inst & 0x1f);
    }
  else
    {
      int max_imm = 1 << nbits;
      int mask = max_imm - 1;
      int sign_bit = max_imm >> 1;

      offset = inst & mask;
      if (is_signed && (offset & sign_bit))
        offset = 0 - (max_imm - offset);
      return offset * scale;
    }
}


/* Fill in values in temp_proc_desc based on the MIPS16 instruction
   stream from start_pc to limit_pc.  */

static void
mips16_heuristic_proc_desc (start_pc, limit_pc, next_frame, sp)
     CORE_ADDR start_pc, limit_pc;
     struct frame_info *next_frame;
     CORE_ADDR sp;
{
  CORE_ADDR cur_pc;
  CORE_ADDR frame_addr = 0;     /* Value of $r17, used as frame pointer */
  unsigned short prev_inst = 0; /* saved copy of previous instruction */
  unsigned inst = 0;            /* current instruction */
  unsigned entry_inst = 0;      /* the entry instruction */
  int reg, offset;

  PROC_FRAME_OFFSET (&temp_proc_desc) = 0;      /* size of stack frame */
  PROC_FRAME_ADJUST (&temp_proc_desc) = 0;      /* offset of FP from SP */

  for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += MIPS16_INSTLEN)
    {
      /* Save the previous instruction.  If it's an EXTEND, we'll extract
         the immediate offset extension from it in mips16_get_imm.  */
      prev_inst = inst;

      /* Fetch and decode the instruction.   */
      inst = (unsigned short) mips_fetch_instruction (cur_pc);
      if ((inst & 0xff00) == 0x6300     /* addiu sp */
          || (inst & 0xff00) == 0xfb00)         /* daddiu sp */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 8, 1);
          if (offset < 0)       /* negative stack adjustment? */
            PROC_FRAME_OFFSET (&temp_proc_desc) -= offset;
          else
            /* Exit loop if a positive stack adjustment is found, which
               usually means that the stack cleanup code in the function
               epilogue is reached.  */
            break;
        }
      else if ((inst & 0xf800) == 0xd000)       /* sw reg,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          reg = mips16_to_32_reg[(inst & 0x700) >> 8];
          PROC_REG_MASK (&temp_proc_desc) |= (1 << reg);
          set_reg_offset (reg, sp + offset);
        }
      else if ((inst & 0xff00) == 0xf900)       /* sd reg,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 8, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          PROC_REG_MASK (&temp_proc_desc) |= (1 << reg);
          set_reg_offset (reg, sp + offset);
        }
      else if ((inst & 0xff00) == 0x6200)       /* sw $ra,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          PROC_REG_MASK (&temp_proc_desc) |= (1 << RA_REGNUM);
          set_reg_offset (RA_REGNUM, sp + offset);
        }
      else if ((inst & 0xff00) == 0xfa00)       /* sd $ra,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 8, 0);
          PROC_REG_MASK (&temp_proc_desc) |= (1 << RA_REGNUM);
          set_reg_offset (RA_REGNUM, sp + offset);
        }
      else if (inst == 0x673d)  /* move $s1, $sp */
        {
          frame_addr = sp;
          PROC_FRAME_REG (&temp_proc_desc) = 17;
        }
      else if ((inst & 0xff00) == 0x0100)       /* addiu $s1,sp,n */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          frame_addr = sp + offset;
          PROC_FRAME_REG (&temp_proc_desc) = 17;
          PROC_FRAME_ADJUST (&temp_proc_desc) = offset;
        }
      else if ((inst & 0xFF00) == 0xd900)       /* sw reg,offset($s1) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 4, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, frame_addr + offset);
        }
      else if ((inst & 0xFF00) == 0x7900)       /* sd reg,offset($s1) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 8, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, frame_addr + offset);
        }
      else if ((inst & 0xf81f) == 0xe809 && (inst & 0x700) != 0x700)    /* entry */
        entry_inst = inst;      /* save for later processing */
      else if ((inst & 0xf800) == 0x1800)       /* jal(x) */
        cur_pc += MIPS16_INSTLEN;       /* 32-bit instruction */
    }

  /* The entry instruction is typically the first instruction in a function,
     and it stores registers at offsets relative to the value of the old SP
     (before the prologue).  But the value of the sp parameter to this
     function is the new SP (after the prologue has been executed).  So we
     can't calculate those offsets until we've seen the entire prologue,
     and can calculate what the old SP must have been. */
  if (entry_inst != 0)
    {
      int areg_count = (entry_inst >> 8) & 7;
      int sreg_count = (entry_inst >> 6) & 3;

      /* The entry instruction always subtracts 32 from the SP.  */
      PROC_FRAME_OFFSET (&temp_proc_desc) += 32;

      /* Now we can calculate what the SP must have been at the
         start of the function prologue.  */
      sp += PROC_FRAME_OFFSET (&temp_proc_desc);

      /* Check if a0-a3 were saved in the caller's argument save area.  */
      for (reg = 4, offset = 0; reg < areg_count + 4; reg++)
        {
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, sp + offset);
          offset += MIPS_SAVED_REGSIZE;
        }

      /* Check if the ra register was pushed on the stack.  */
      offset = -4;
      if (entry_inst & 0x20)
        {
          PROC_REG_MASK (&temp_proc_desc) |= 1 << RA_REGNUM;
          set_reg_offset (RA_REGNUM, sp + offset);
          offset -= MIPS_SAVED_REGSIZE;
        }

      /* Check if the s0 and s1 registers were pushed on the stack.  */
      for (reg = 16; reg < sreg_count + 16; reg++)
        {
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, sp + offset);
          offset -= MIPS_SAVED_REGSIZE;
        }
    }
}

static void
mips32_heuristic_proc_desc (start_pc, limit_pc, next_frame, sp)
     CORE_ADDR start_pc, limit_pc;
     struct frame_info *next_frame;
     CORE_ADDR sp;
{
  CORE_ADDR cur_pc;
  CORE_ADDR frame_addr = 0;     /* Value of $r30. Used by gcc for frame-pointer */
restart:
  memset (temp_saved_regs, '\0', SIZEOF_FRAME_SAVED_REGS);
  PROC_FRAME_OFFSET (&temp_proc_desc) = 0;
  PROC_FRAME_ADJUST (&temp_proc_desc) = 0;      /* offset of FP from SP */
  for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += MIPS_INSTLEN)
    {
      unsigned long inst, high_word, low_word;
      int reg;

      /* Fetch the instruction.   */
      inst = (unsigned long) mips_fetch_instruction (cur_pc);

      /* Save some code by pre-extracting some useful fields.  */
      high_word = (inst >> 16) & 0xffff;
      low_word = inst & 0xffff;
      reg = high_word & 0x1f;

      if (high_word == 0x27bd   /* addiu $sp,$sp,-i */
          || high_word == 0x23bd        /* addi $sp,$sp,-i */
          || high_word == 0x67bd)       /* daddiu $sp,$sp,-i */
        {
          if (low_word & 0x8000)        /* negative stack adjustment? */
            PROC_FRAME_OFFSET (&temp_proc_desc) += 0x10000 - low_word;
          else
            /* Exit loop if a positive stack adjustment is found, which
               usually means that the stack cleanup code in the function
               epilogue is reached.  */
            break;
        }
      else if ((high_word & 0xFFE0) == 0xafa0)  /* sw reg,offset($sp) */
        {
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, sp + low_word);
        }
      else if ((high_word & 0xFFE0) == 0xffa0)  /* sd reg,offset($sp) */
        {
          /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and $ra,
             but the register size used is only 32 bits. Make the address
             for the saved register point to the lower 32 bits.  */
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, sp + low_word + 8 - MIPS_REGSIZE);
        }
      else if (high_word == 0x27be)     /* addiu $30,$sp,size */
        {
          /* Old gcc frame, r30 is virtual frame pointer.  */
          if ((long) low_word != PROC_FRAME_OFFSET (&temp_proc_desc))
            frame_addr = sp + low_word;
          else if (PROC_FRAME_REG (&temp_proc_desc) == SP_REGNUM)
            {
              unsigned alloca_adjust;
              PROC_FRAME_REG (&temp_proc_desc) = 30;
              frame_addr = read_next_frame_reg (next_frame, 30);
              alloca_adjust = (unsigned) (frame_addr - (sp + low_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;
                }
            }
        }
      /* move $30,$sp.  With different versions of gas this will be either
         `addu $30,$sp,$zero' or `or $30,$sp,$zero' or `daddu 30,sp,$0'.
         Accept any one of these.  */
      else if (inst == 0x03A0F021 || inst == 0x03a0f025 || inst == 0x03a0f02d)
        {
          /* New gcc frame, virtual frame pointer is at r30 + frame_size.  */
          if (PROC_FRAME_REG (&temp_proc_desc) == SP_REGNUM)
            {
              unsigned alloca_adjust;
              PROC_FRAME_REG (&temp_proc_desc) = 30;
              frame_addr = read_next_frame_reg (next_frame, 30);
              alloca_adjust = (unsigned) (frame_addr - sp);
              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 ((high_word & 0xFFE0) == 0xafc0)  /* sw reg,offset($30) */
        {
          PROC_REG_MASK (&temp_proc_desc) |= 1 << reg;
          set_reg_offset (reg, frame_addr + low_word);
        }
    }
}

static mips_extra_func_info_t
heuristic_proc_desc (start_pc, limit_pc, next_frame)
     CORE_ADDR start_pc, limit_pc;
     struct frame_info *next_frame;
{
  CORE_ADDR sp = read_next_frame_reg (next_frame, SP_REGNUM);

  if (start_pc == 0)
    return NULL;
  memset (&temp_proc_desc, '\0', sizeof (temp_proc_desc));
  memset (&temp_saved_regs, '\0', SIZEOF_FRAME_SAVED_REGS);
  PROC_LOW_ADDR (&temp_proc_desc) = start_pc;
  PROC_FRAME_REG (&temp_proc_desc) = SP_REGNUM;
  PROC_PC_REG (&temp_proc_desc) = RA_REGNUM;

  if (start_pc + 200 < limit_pc)
    limit_pc = start_pc + 200;
  if (pc_is_mips16 (start_pc))
    mips16_heuristic_proc_desc (start_pc, limit_pc, next_frame, sp);
  else
    mips32_heuristic_proc_desc (start_pc, limit_pc, next_frame, sp);
  return &temp_proc_desc;
}

static mips_extra_func_info_t
non_heuristic_proc_desc (pc, addrptr)
     CORE_ADDR pc;
     CORE_ADDR *addrptr;
{
  CORE_ADDR startaddr;
  mips_extra_func_info_t proc_desc;
  struct block *b = block_for_pc (pc);
  struct symbol *sym;

  find_pc_partial_function (pc, NULL, &startaddr, NULL);
  if (addrptr)
    *addrptr = startaddr;
  if (b == NULL || PC_IN_CALL_DUMMY (pc, 0, 0))
    sym = NULL;
  else
    {
      if (startaddr > BLOCK_START (b))
        /* This is the "pathological" case referred to in a comment in
           print_frame_info.  It might be better to move this check into
           symbol reading.  */
        sym = NULL;
      else
        sym = lookup_symbol (MIPS_EFI_SYMBOL_NAME, b, LABEL_NAMESPACE, 0, NULL);
    }

  /* If we never found a PDR for this function in symbol reading, then
     examine prologues to find the information.  */
  if (sym)
    {
      proc_desc = (mips_extra_func_info_t) SYMBOL_VALUE (sym);
      if (PROC_FRAME_REG (proc_desc) == -1)
        return NULL;
      else
        return proc_desc;
    }
  else
    return NULL;
}


static mips_extra_func_info_t
find_proc_desc (pc, next_frame)
     CORE_ADDR pc;
     struct frame_info *next_frame;
{
  mips_extra_func_info_t proc_desc;
  CORE_ADDR startaddr;

  proc_desc = non_heuristic_proc_desc (pc, &startaddr);

  if (proc_desc)
    {
      /* 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 "heuristic" proc_desc (by analyzing
       * the actual code) to replace the "official" proc_desc.
       */
      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
    {
      /* Is linked_proc_desc_table really necessary?  It only seems to be used
         by procedure call dummys.  However, the procedures being called ought
         to have their own proc_descs, and even if they don't,
         heuristic_proc_desc knows how to create them! */

      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;

      if (startaddr == 0)
        startaddr = heuristic_proc_start (pc);

      proc_desc =
        heuristic_proc_desc (startaddr, pc, next_frame);
    }
  return proc_desc;
}

static CORE_ADDR
get_frame_pointer (frame, proc_desc)
     struct frame_info *frame;
     mips_extra_func_info_t proc_desc;
{
  return ADDR_BITS_REMOVE (
                   read_next_frame_reg (frame, PROC_FRAME_REG (proc_desc)) +
             PROC_FRAME_OFFSET (proc_desc) - PROC_FRAME_ADJUST (proc_desc));
}

mips_extra_func_info_t cached_proc_desc;

CORE_ADDR
mips_frame_chain (frame)
     struct frame_info *frame;
{
  mips_extra_func_info_t proc_desc;
  CORE_ADDR tmp;
  CORE_ADDR saved_pc = FRAME_SAVED_PC (frame);

  if (saved_pc == 0 || inside_entry_file (saved_pc))
    return 0;

  /* Check if the PC is inside a call stub.  If it is, fetch the
     PC of the caller of that stub.  */
  if ((tmp = mips_skip_stub (saved_pc)) != 0)
    saved_pc = tmp;

  /* Look up the procedure descriptor for this PC.  */
  proc_desc = find_proc_desc (saved_pc, frame);
  if (!proc_desc)
    return 0;

  cached_proc_desc = proc_desc;

  /* If no frame pointer and frame size is zero, we must be at end
     of stack (or otherwise hosed).  If we don't check frame size,
     we loop forever if we see a zero size frame.  */
  if (PROC_FRAME_REG (proc_desc) == SP_REGNUM
      && PROC_FRAME_OFFSET (proc_desc) == 0
  /* The previous frame from a sigtramp frame might be frameless
     and have frame size zero.  */
      && !frame->signal_handler_caller)
    return 0;
  else
    return get_frame_pointer (frame, proc_desc);
}

void
mips_init_extra_frame_info (fromleaf, fci)
     int fromleaf;
     struct frame_info *fci;
{
  int regnum;

  /* 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->extra_info = (struct frame_extra_info *)
    frame_obstack_alloc (sizeof (struct frame_extra_info));

  fci->saved_regs = NULL;
  fci->extra_info->proc_desc =
    proc_desc == &temp_proc_desc ? 0 : proc_desc;
  if (proc_desc)
    {
      /* Fixup frame-pointer - only needed for top frame */
      /* This may not be quite right, if proc has a real frame register.
         Get the value of the frame relative sp, procedure might have been
         interrupted by a signal at it's very start.  */
      if (fci->pc == PROC_LOW_ADDR (proc_desc)
          && !PROC_DESC_IS_DUMMY (proc_desc))
        fci->frame = read_next_frame_reg (fci->next, SP_REGNUM);
      else
        fci->frame = get_frame_pointer (fci->next, proc_desc);

      if (proc_desc == &temp_proc_desc)
        {
          char *name;

          /* Do not set the saved registers for a sigtramp frame,
             mips_find_saved_registers will do that for us.
             We can't use fci->signal_handler_caller, it is not yet set.  */
          find_pc_partial_function (fci->pc, &name,
                                    (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
          if (!IN_SIGTRAMP (fci->pc, name))
            {
              frame_saved_regs_zalloc (fci);
              memcpy (fci->saved_regs, temp_saved_regs, SIZEOF_FRAME_SAVED_REGS);
              fci->saved_regs[PC_REGNUM]
                = fci->saved_regs[RA_REGNUM];
            }
        }

      /* hack: if argument regs are saved, guess these contain args */
      /* assume we can't tell how many args for now */
      fci->extra_info->num_args = -1;
      for (regnum = MIPS_LAST_ARG_REGNUM; regnum >= A0_REGNUM; regnum--)
        {
          if (PROC_REG_MASK (proc_desc) & (1 << regnum))
            {
              fci->extra_info->num_args = regnum - A0_REGNUM + 1;
              break;
            }
        }
    }
}

/* MIPS stack frames are almost impenetrable.  When execution stops,
   we basically have to look at symbol information for the function
   that we stopped in, which tells us *which* register (if any) is
   the base of the frame pointer, and what offset from that register
   the frame itself is at.  

   This presents a problem when trying to examine a stack in memory
   (that isn't executing at the moment), using the "frame" command.  We
   don't have a PC, nor do we have any registers except SP.

   This routine takes two arguments, SP and PC, and tries to make the
   cached frames look as if these two arguments defined a frame on the
   cache.  This allows the rest of info frame to extract the important
   arguments without difficulty.  */

struct frame_info *
setup_arbitrary_frame (argc, argv)
     int argc;
     CORE_ADDR *argv;
{
  if (argc != 2)
    error ("MIPS frame specifications require two arguments: sp and pc");

  return create_new_frame (argv[0], argv[1]);
}

/*
 * STACK_ARGSIZE -- how many bytes does a pushed function arg take up on the stack?
 *
 * For n32 ABI, eight.
 * For all others, he same as the size of a general register.
 */
#if defined (_MIPS_SIM_NABI32) && _MIPS_SIM == _MIPS_SIM_NABI32
#define MIPS_NABI32   1
#define STACK_ARGSIZE 8
#else
#define MIPS_NABI32   0
#define STACK_ARGSIZE MIPS_SAVED_REGSIZE
#endif

CORE_ADDR
mips_push_arguments (nargs, args, sp, struct_return, struct_addr)
     int nargs;
     value_ptr *args;
     CORE_ADDR sp;
     int struct_return;
     CORE_ADDR struct_addr;
{
  int argreg;
  int float_argreg;
  int argnum;
  int len = 0;
  int stack_offset = 0;

  /* Macros to round N up or down to the next A boundary; A must be
     a power of two. */
#define ROUND_DOWN(n,a) ((n) & ~((a)-1))
#define ROUND_UP(n,a) (((n)+(a)-1) & ~((a)-1))

  /* First ensure that the stack and structure return address (if any)
     are properly aligned. The stack has to be at least 64-bit aligned
     even on 32-bit machines, because doubles must be 64-bit aligned.
     On at least one MIPS variant, stack frames need to be 128-bit
     aligned, so we round to this widest known alignment. */
  sp = ROUND_DOWN (sp, 16);
  struct_addr = ROUND_DOWN (struct_addr, MIPS_SAVED_REGSIZE);

  /* Now make space on the stack for the args. We allocate more
     than necessary for EABI, because the first few arguments are
     passed in registers, but that's OK. */
  for (argnum = 0; argnum < nargs; argnum++)
    len += ROUND_UP (TYPE_LENGTH (VALUE_TYPE (args[argnum])), MIPS_SAVED_REGSIZE);
  sp -= ROUND_UP (len, 16);

  /* Initialize the integer and float register pointers.  */
  argreg = A0_REGNUM;
  float_argreg = FPA0_REGNUM;

  /* the struct_return pointer occupies the first parameter-passing reg */
  if (struct_return)
    write_register (argreg++, struct_addr);

  /* Now load as many as possible of the first arguments into
     registers, and push the rest onto the stack.  Loop thru args
     from first to last.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      char *val;
      char valbuf[MAX_REGISTER_RAW_SIZE];
      value_ptr arg = args[argnum];
      struct type *arg_type = check_typedef (VALUE_TYPE (arg));
      int len = TYPE_LENGTH (arg_type);
      enum type_code typecode = TYPE_CODE (arg_type);

      /* The EABI passes structures that do not fit in a register by
         reference. In all other cases, pass the structure by value.  */
      if (MIPS_EABI && len > MIPS_SAVED_REGSIZE &&
          (typecode == TYPE_CODE_STRUCT || typecode == TYPE_CODE_UNION))
        {
          store_address (valbuf, MIPS_SAVED_REGSIZE, VALUE_ADDRESS (arg));
          typecode = TYPE_CODE_PTR;
          len = MIPS_SAVED_REGSIZE;
          val = valbuf;
        }
      else
        val = (char *) VALUE_CONTENTS (arg);

      /* 32-bit ABIs always start floating point arguments in an
         even-numbered floating point register.   */
      if (!FP_REGISTER_DOUBLE && typecode == TYPE_CODE_FLT
          && (float_argreg & 1))
        float_argreg++;

      /* Floating point arguments passed in registers have to be
         treated specially.  On 32-bit architectures, doubles
         are passed in register pairs; the even register gets
         the low word, and the odd register gets the high word.
         On non-EABI processors, the first two floating point arguments are
         also copied to general registers, because MIPS16 functions
         don't use float registers for arguments.  This duplication of
         arguments in general registers can't hurt non-MIPS16 functions
         because those registers are normally skipped.  */
      if (typecode == TYPE_CODE_FLT
          && float_argreg <= MIPS_LAST_FP_ARG_REGNUM
          && MIPS_FPU_TYPE != MIPS_FPU_NONE)
        {
          if (!FP_REGISTER_DOUBLE && len == 8)
            {
              int low_offset = TARGET_BYTE_ORDER == BIG_ENDIAN ? 4 : 0;
              unsigned long regval;

              /* Write the low word of the double to the even register(s).  */
              regval = extract_unsigned_integer (val + low_offset, 4);
              write_register (float_argreg++, regval);
              if (!MIPS_EABI)
                write_register (argreg + 1, regval);

              /* Write the high word of the double to the odd register(s).  */
              regval = extract_unsigned_integer (val + 4 - low_offset, 4);
              write_register (float_argreg++, regval);
              if (!MIPS_EABI)
                {
                  write_register (argreg, regval);
                  argreg += 2;
                }

            }
          else
            {
              /* This is a floating point value that fits entirely
                 in a single register.  */
              CORE_ADDR regval = extract_address (val, len);
              write_register (float_argreg++, regval);
              if (!MIPS_EABI)
                {
                  write_register (argreg, regval);
                  argreg += FP_REGISTER_DOUBLE ? 1 : 2;
                }
            }
        }
      else
        {
          /* Copy the argument to general registers or the stack in
             register-sized pieces.  Large arguments are split between
             registers and stack.  */
          /* Note: structs whose size is not a multiple of MIPS_REGSIZE
             are treated specially: Irix cc passes them in registers
             where gcc sometimes puts them on the stack.  For maximum
             compatibility, we will put them in both places.  */

          int odd_sized_struct = ((len > MIPS_SAVED_REGSIZE) &&
                                  (len % MIPS_SAVED_REGSIZE != 0));
          while (len > 0)
            {
              int partial_len = len < MIPS_SAVED_REGSIZE ? len : MIPS_SAVED_REGSIZE;

              if (argreg > MIPS_LAST_ARG_REGNUM || odd_sized_struct)
                {
                  /* Write this portion of the argument to the stack.  */
                  /* Should shorter than int integer values be
                     promoted to int before being stored? */

                  int longword_offset = 0;
                  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
                    {
                      if (STACK_ARGSIZE == 8 &&
                          (typecode == TYPE_CODE_INT ||
                           typecode == TYPE_CODE_PTR ||
                           typecode == TYPE_CODE_FLT) && len <= 4)
                        longword_offset = STACK_ARGSIZE - len;
                      else if ((typecode == TYPE_CODE_STRUCT ||
                                typecode == TYPE_CODE_UNION) &&
                               TYPE_LENGTH (arg_type) < STACK_ARGSIZE)
                        longword_offset = STACK_ARGSIZE - len;
                    }

                  write_memory (sp + stack_offset + longword_offset,
                                val, partial_len);
                }

              /* Note!!! This is NOT an else clause.
                 Odd sized structs may go thru BOTH paths.  */
              if (argreg <= MIPS_LAST_ARG_REGNUM)
                {
                  CORE_ADDR regval = extract_address (val, partial_len);

                  /* A non-floating-point argument being passed in a 
                     general register.  If a struct or union, and if
                     the remaining length is smaller than the register
                     size, we have to adjust the register value on
                     big endian targets.

                     It does not seem to be necessary to do the
                     same for integral types.

                     Also don't do this adjustment on EABI and O64
                     binaries. */

                  if (!MIPS_EABI
                      && MIPS_SAVED_REGSIZE < 8
                      && TARGET_BYTE_ORDER == BIG_ENDIAN
                      && partial_len < MIPS_SAVED_REGSIZE
                      && (typecode == TYPE_CODE_STRUCT ||
                          typecode == TYPE_CODE_UNION))
                    regval <<= ((MIPS_SAVED_REGSIZE - partial_len) *
                                TARGET_CHAR_BIT);

                  write_register (argreg, regval);
                  argreg++;

                  /* If this is the old ABI, prevent subsequent floating
                     point arguments from being passed in floating point
                     registers.  */
                  if (!MIPS_EABI)
                    float_argreg = MIPS_LAST_FP_ARG_REGNUM + 1;
                }

              len -= partial_len;
              val += partial_len;

              /* The offset onto the stack at which we will start
                 copying parameters (after the registers are used up) 
                 begins at (4 * MIPS_REGSIZE) in the old ABI.  This 
                 leaves room for the "home" area for register parameters.

                 In the new EABI (and the NABI32), the 8 register parameters 
                 do not have "home" stack space reserved for them, so the
                 stack offset does not get incremented until after
                 we have used up the 8 parameter registers.  */

              if (!(MIPS_EABI || MIPS_NABI32) ||
                  argnum >= 8)
                stack_offset += ROUND_UP (partial_len, STACK_ARGSIZE);
            }
        }
    }

  /* Return adjusted stack pointer.  */
  return sp;
}

CORE_ADDR
mips_push_return_address (pc, sp)
     CORE_ADDR pc;
     CORE_ADDR sp;
{
  /* Set the return address register to point to the entry
     point of the program, where a breakpoint lies in wait.  */
  write_register (RA_REGNUM, CALL_DUMMY_ADDRESS ());
  return sp;
}

static void
mips_push_register (CORE_ADDR * sp, int regno)
{
  char buffer[MAX_REGISTER_RAW_SIZE];
  int regsize;
  int offset;
  if (MIPS_SAVED_REGSIZE < REGISTER_RAW_SIZE (regno))
    {
      regsize = MIPS_SAVED_REGSIZE;
      offset = (TARGET_BYTE_ORDER == BIG_ENDIAN
                ? REGISTER_RAW_SIZE (regno) - MIPS_SAVED_REGSIZE
                : 0);
    }
  else
    {
      regsize = REGISTER_RAW_SIZE (regno);
      offset = 0;
    }
  *sp -= regsize;
  read_register_gen (regno, buffer);
  write_memory (*sp, buffer + offset, regsize);
}

/* MASK(i,j) == (1<<i) + (1<<(i+1)) + ... + (1<<j)). Assume i<=j<(MIPS_NUMREGS-1). */
#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 = ADDR_BITS_REMOVE (read_register (SP_REGNUM));
  CORE_ADDR old_sp = sp;
  link->next = linked_proc_desc_table;
  linked_proc_desc_table = link;

/* FIXME!   are these correct ? */
#define PUSH_FP_REGNUM 16       /* must be a register preserved across calls */
#define GEN_REG_SAVE_MASK MASK(1,16)|MASK(24,28)|(1<<(MIPS_NUMREGS-1))
#define FLOAT_REG_SAVE_MASK MASK(0,19)
#define FLOAT_SINGLE_REG_SAVE_MASK \
  ((1<<18)|(1<<16)|(1<<14)|(1<<12)|(1<<10)|(1<<8)|(1<<6)|(1<<4)|(1<<2)|(1<<0))
  /*
   * 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, PUSH_FP_REGNUM, MMLO/-HI
   * and FP Control/Status registers.
   * 
   *
   * 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)
   *    Argument build area and stack arguments written via mips_push_arguments
   *  (low memory)
   */

  /* Save special registers (PC, MMHI, MMLO, FPC_CSR) */
  PROC_FRAME_REG (proc_desc) = PUSH_FP_REGNUM;
  PROC_FRAME_OFFSET (proc_desc) = 0;
  PROC_FRAME_ADJUST (proc_desc) = 0;
  mips_push_register (&sp, PC_REGNUM);
  mips_push_register (&sp, HI_REGNUM);
  mips_push_register (&sp, LO_REGNUM);
  mips_push_register (&sp, MIPS_FPU_TYPE == MIPS_FPU_NONE ? 0 : FCRCS_REGNUM);

  /* Save general CPU registers */
  PROC_REG_MASK (proc_desc) = GEN_REG_SAVE_MASK;
  /* PROC_REG_OFFSET is the offset of the first saved register from FP.  */
  PROC_REG_OFFSET (proc_desc) = sp - old_sp - MIPS_SAVED_REGSIZE;
  for (ireg = 32; --ireg >= 0;)
    if (PROC_REG_MASK (proc_desc) & (1 << ireg))
      mips_push_register (&sp, ireg);

  /* Save floating point registers starting with high order word */
  PROC_FREG_MASK (proc_desc) =
    MIPS_FPU_TYPE == MIPS_FPU_DOUBLE ? FLOAT_REG_SAVE_MASK
    : MIPS_FPU_TYPE == MIPS_FPU_SINGLE ? FLOAT_SINGLE_REG_SAVE_MASK : 0;
  /* PROC_FREG_OFFSET is the offset of the first saved *double* register
     from FP.  */
  PROC_FREG_OFFSET (proc_desc) = sp - old_sp - 8;
  for (ireg = 32; --ireg >= 0;)
    if (PROC_FREG_MASK (proc_desc) & (1 << ireg))
      mips_push_register (&sp, ireg + FP0_REGNUM);

  /* Update the frame pointer for the call dummy and the stack pointer.
     Set the procedure's starting and ending addresses to point to the
     call dummy address at the entry point.  */
  write_register (PUSH_FP_REGNUM, old_sp);
  write_register (SP_REGNUM, sp);
  PROC_LOW_ADDR (proc_desc) = CALL_DUMMY_ADDRESS ();
  PROC_HIGH_ADDR (proc_desc) = CALL_DUMMY_ADDRESS () + 4;
  SET_PROC_DESC_IS_DUMMY (proc_desc);
  PROC_PC_REG (proc_desc) = RA_REGNUM;
}

void
mips_pop_frame ()
{
  register int regnum;
  struct frame_info *frame = get_current_frame ();
  CORE_ADDR new_sp = FRAME_FP (frame);

  mips_extra_func_info_t proc_desc = frame->extra_info->proc_desc;

  write_register (PC_REGNUM, FRAME_SAVED_PC (frame));
  if (frame->saved_regs == NULL)
    mips_find_saved_regs (frame);
  for (regnum = 0; regnum < NUM_REGS; regnum++)
    {
      if (regnum != SP_REGNUM && regnum != PC_REGNUM
          && frame->saved_regs[regnum])
        write_register (regnum,
                        read_memory_integer (frame->saved_regs[regnum],
                                             MIPS_SAVED_REGSIZE));
    }
  write_register (SP_REGNUM, new_sp);
  flush_cached_frames ();

  if (proc_desc && PROC_DESC_IS_DUMMY (proc_desc))
    {
      struct linked_proc_info *pi_ptr, *prev_ptr;

      for (pi_ptr = linked_proc_desc_table, prev_ptr = NULL;
           pi_ptr != NULL;
           prev_ptr = pi_ptr, pi_ptr = pi_ptr->next)
        {
          if (&pi_ptr->info == proc_desc)
            break;
        }

      if (pi_ptr == NULL)
        error ("Can't locate dummy extra frame info\n");

      if (prev_ptr != NULL)
        prev_ptr->next = pi_ptr->next;
      else
        linked_proc_desc_table = pi_ptr->next;

      free (pi_ptr);

      write_register (HI_REGNUM,
                      read_memory_integer (new_sp - 2 * MIPS_SAVED_REGSIZE,
                                           MIPS_SAVED_REGSIZE));
      write_register (LO_REGNUM,
                      read_memory_integer (new_sp - 3 * MIPS_SAVED_REGSIZE,
                                           MIPS_SAVED_REGSIZE));
      if (MIPS_FPU_TYPE != MIPS_FPU_NONE)
        write_register (FCRCS_REGNUM,
                        read_memory_integer (new_sp - 4 * MIPS_SAVED_REGSIZE,
                                             MIPS_SAVED_REGSIZE));
    }
}

static void
mips_print_register (regnum, all)
     int regnum, all;
{
  char raw_buffer[MAX_REGISTER_RAW_SIZE];

  /* Get the data in raw format.  */
  if (read_relative_register_raw_bytes (regnum, raw_buffer))
    {
      printf_filtered ("%s: [Invalid]", REGISTER_NAME (regnum));
      return;
    }

  /* If an even floating point register, also print as double. */
  if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT
      && !((regnum - FP0_REGNUM) & 1))
    if (REGISTER_RAW_SIZE (regnum) == 4)        /* this would be silly on MIPS64 or N32 (Irix 6) */
      {
        char dbuffer[2 * MAX_REGISTER_RAW_SIZE];

        read_relative_register_raw_bytes (regnum, dbuffer);
        read_relative_register_raw_bytes (regnum + 1, dbuffer + MIPS_REGSIZE);
        REGISTER_CONVERT_TO_TYPE (regnum, builtin_type_double, dbuffer);

        printf_filtered ("(d%d: ", regnum - FP0_REGNUM);
        val_print (builtin_type_double, dbuffer, 0, 0,
                   gdb_stdout, 0, 1, 0, Val_pretty_default);
        printf_filtered ("); ");
      }
  fputs_filtered (REGISTER_NAME (regnum), gdb_stdout);

  /* The problem with printing numeric register names (r26, etc.) is that
     the user can't use them on input.  Probably the best solution is to
     fix it so that either the numeric or the funky (a2, etc.) names
     are accepted on input.  */
  if (regnum < MIPS_NUMREGS)
    printf_filtered ("(r%d): ", regnum);
  else
    printf_filtered (": ");

  /* If virtual format is floating, print it that way.  */
  if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT)
    if (FP_REGISTER_DOUBLE)
      {                         /* show 8-byte floats as float AND double: */
        int offset = 4 * (TARGET_BYTE_ORDER == BIG_ENDIAN);

        printf_filtered (" (float) ");
        val_print (builtin_type_float, raw_buffer + offset, 0, 0,
                   gdb_stdout, 0, 1, 0, Val_pretty_default);
        printf_filtered (", (double) ");
        val_print (builtin_type_double, raw_buffer, 0, 0,
                   gdb_stdout, 0, 1, 0, Val_pretty_default);
      }
    else
      val_print (REGISTER_VIRTUAL_TYPE (regnum), raw_buffer, 0, 0,
                 gdb_stdout, 0, 1, 0, Val_pretty_default);
  /* Else print as integer in hex.  */
  else
    print_scalar_formatted (raw_buffer, REGISTER_VIRTUAL_TYPE (regnum),
                            'x', 0, gdb_stdout);
}

/* Replacement for generic do_registers_info.  
   Print regs in pretty columns.  */

static int
do_fp_register_row (regnum)
     int regnum;
{                               /* do values for FP (float) regs */
  char *raw_buffer[2];
  char *dbl_buffer;
  /* use HI and LO to control the order of combining two flt regs */
  int HI = (TARGET_BYTE_ORDER == BIG_ENDIAN);
  int LO = (TARGET_BYTE_ORDER != BIG_ENDIAN);
  double doub, flt1, flt2;      /* doubles extracted from raw hex data */
  int inv1, inv2, inv3;

  raw_buffer[0] = (char *) alloca (REGISTER_RAW_SIZE (FP0_REGNUM));
  raw_buffer[1] = (char *) alloca (REGISTER_RAW_SIZE (FP0_REGNUM));
  dbl_buffer = (char *) alloca (2 * REGISTER_RAW_SIZE (FP0_REGNUM));

  /* Get the data in raw format.  */
  if (read_relative_register_raw_bytes (regnum, raw_buffer[HI]))
    error ("can't read register %d (%s)", regnum, REGISTER_NAME (regnum));
  if (REGISTER_RAW_SIZE (regnum) == 4)
    {
      /* 4-byte registers: we can fit two registers per row. */
      /* Also print every pair of 4-byte regs as an 8-byte double. */
      if (read_relative_register_raw_bytes (regnum + 1, raw_buffer[LO]))
        error ("can't read register %d (%s)",
               regnum + 1, REGISTER_NAME (regnum + 1));

      /* copy the two floats into one double, and unpack both */
      memcpy (dbl_buffer, raw_buffer, sizeof (dbl_buffer));
      flt1 = unpack_double (builtin_type_float, raw_buffer[HI], &inv1);
      flt2 = unpack_double (builtin_type_float, raw_buffer[LO], &inv2);
      doub = unpack_double (builtin_type_double, dbl_buffer, &inv3);

      printf_filtered (inv1 ? " %-5s: <invalid float>" :
                       " %-5s%-17.9g", REGISTER_NAME (regnum), flt1);
      printf_filtered (inv2 ? " %-5s: <invalid float>" :
                       " %-5s%-17.9g", REGISTER_NAME (regnum + 1), flt2);
      printf_filtered (inv3 ? " dbl: <invalid double>\n" :
                       " dbl: %-24.17g\n", doub);
      /* may want to do hex display here (future enhancement) */
      regnum += 2;
    }
  else
    {                           /* eight byte registers: print each one as float AND as double. */
      int offset = 4 * (TARGET_BYTE_ORDER == BIG_ENDIAN);

      memcpy (dbl_buffer, raw_buffer[HI], sizeof (dbl_buffer));
      flt1 = unpack_double (builtin_type_float,
                            &raw_buffer[HI][offset], &inv1);
      doub = unpack_double (builtin_type_double, dbl_buffer, &inv3);

      printf_filtered (inv1 ? " %-5s: <invalid float>" :
                       " %-5s flt: %-17.9g", REGISTER_NAME (regnum), flt1);
      printf_filtered (inv3 ? " dbl: <invalid double>\n" :
                       " dbl: %-24.17g\n", doub);
      /* may want to do hex display here (future enhancement) */
      regnum++;
    }
  return regnum;
}

/* Print a row's worth of GP (int) registers, with name labels above */

static int
do_gp_register_row (regnum)
     int regnum;
{
  /* do values for GP (int) regs */
  char raw_buffer[MAX_REGISTER_RAW_SIZE];
  int ncols = (MIPS_REGSIZE == 8 ? 4 : 8);      /* display cols per row */
  int col, byte;
  int start_regnum = regnum;
  int numregs = NUM_REGS;


  /* For GP registers, we print a separate row of names above the vals */
  printf_filtered ("     ");
  for (col = 0; col < ncols && regnum < numregs; regnum++)
    {
      if (*REGISTER_NAME (regnum) == '\0')
        continue;               /* unused register */
      if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT)
        break;                  /* end the row: reached FP register */
      printf_filtered (MIPS_REGSIZE == 8 ? "%17s" : "%9s",
                       REGISTER_NAME (regnum));
      col++;
    }
  printf_filtered (start_regnum < MIPS_NUMREGS ? "\n R%-4d" : "\n      ",
                   start_regnum);       /* print the R0 to R31 names */

  regnum = start_regnum;        /* go back to start of row */
  /* now print the values in hex, 4 or 8 to the row */
  for (col = 0; col < ncols && regnum < numregs; regnum++)
    {
      if (*REGISTER_NAME (regnum) == '\0')
        continue;               /* unused register */
      if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT)
        break;                  /* end row: reached FP register */
      /* OK: get the data in raw format.  */
      if (read_relative_register_raw_bytes (regnum, raw_buffer))
        error ("can't read register %d (%s)", regnum, REGISTER_NAME (regnum));
      /* pad small registers */
      for (byte = 0; byte < (MIPS_REGSIZE - REGISTER_VIRTUAL_SIZE (regnum)); byte++)
        printf_filtered ("  ");
      /* Now print the register value in hex, endian order. */
      if (TARGET_BYTE_ORDER == BIG_ENDIAN)
        for (byte = REGISTER_RAW_SIZE (regnum) - REGISTER_VIRTUAL_SIZE (regnum);
             byte < REGISTER_RAW_SIZE (regnum);
             byte++)
          printf_filtered ("%02x", (unsigned char) raw_buffer[byte]);
      else
        for (byte = REGISTER_VIRTUAL_SIZE (regnum) - 1;
             byte >= 0;
             byte--)
          printf_filtered ("%02x", (unsigned char) raw_buffer[byte]);
      printf_filtered (" ");
      col++;
    }
  if (col > 0)                  /* ie. if we actually printed anything... */
    printf_filtered ("\n");

  return regnum;
}

/* MIPS_DO_REGISTERS_INFO(): called by "info register" command */

void
mips_do_registers_info (regnum, fpregs)
     int regnum;
     int fpregs;
{
  if (regnum != -1)             /* do one specified register */
    {
      if (*(REGISTER_NAME (regnum)) == '\0')
        error ("Not a valid register for the current processor type");

      mips_print_register (regnum, 0);
      printf_filtered ("\n");
    }
  else
    /* do all (or most) registers */
    {
      regnum = 0;
      while (regnum < NUM_REGS)
        {
          if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT)
            if (fpregs)         /* true for "INFO ALL-REGISTERS" command */
              regnum = do_fp_register_row (regnum);     /* FP regs */
            else
              regnum += MIPS_NUMREGS;   /* skip floating point regs */
          else
            regnum = do_gp_register_row (regnum);       /* GP (int) regs */
        }
    }
}

/* Return number of args passed to a frame. described by FIP.
   Can return -1, meaning no way to tell.  */

int
mips_frame_num_args (frame)
     struct frame_info *frame;
{
#if 0                           /* FIXME Use or lose this! */
  struct chain_info_t *p;

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

/* Is this a branch with a delay slot?  */

static int is_delayed PARAMS ((unsigned long));

static int
is_delayed (insn)
     unsigned long insn;
{
  int i;
  for (i = 0; i < NUMOPCODES; ++i)
    if (mips_opcodes[i].pinfo != INSN_MACRO
        && (insn & mips_opcodes[i].mask) == mips_opcodes[i].match)
      break;
  return (i < NUMOPCODES
          && (mips_opcodes[i].pinfo & (INSN_UNCOND_BRANCH_DELAY
                                       | INSN_COND_BRANCH_DELAY
                                       | INSN_COND_BRANCH_LIKELY)));
}

int
mips_step_skips_delay (pc)
     CORE_ADDR pc;
{
  char buf[MIPS_INSTLEN];

  /* There is no branch delay slot on MIPS16.  */
  if (pc_is_mips16 (pc))
    return 0;

  if (target_read_memory (pc, buf, MIPS_INSTLEN) != 0)
    /* If error reading memory, guess that it is not a delayed branch.  */
    return 0;
  return is_delayed ((unsigned long) extract_unsigned_integer (buf, MIPS_INSTLEN));
}


/* Skip the PC past function prologue instructions (32-bit version).
   This is a helper function for mips_skip_prologue.  */

static CORE_ADDR
mips32_skip_prologue (pc, lenient)
     CORE_ADDR pc;              /* starting PC to search from */
     int lenient;
{
  t_inst inst;
  CORE_ADDR end_pc;
  int seen_sp_adjust = 0;
  int load_immediate_bytes = 0;

  /* Skip the typical prologue instructions. These are the stack adjustment
     instruction and the instructions that save registers on the stack
     or in the gcc frame.  */
  for (end_pc = pc + 100; pc < end_pc; pc += MIPS_INSTLEN)
    {
      unsigned long high_word;

      inst = mips_fetch_instruction (pc);
      high_word = (inst >> 16) & 0xffff;

#if 0
      if (lenient && is_delayed (inst))
        continue;
#endif

      if (high_word == 0x27bd   /* addiu $sp,$sp,offset */
          || high_word == 0x67bd)       /* daddiu $sp,$sp,offset */
        seen_sp_adjust = 1;
      else if (inst == 0x03a1e823 ||    /* subu $sp,$sp,$at */
               inst == 0x03a8e823)      /* subu $sp,$sp,$t0 */
        seen_sp_adjust = 1;
      else if (((inst & 0xFFE00000) == 0xAFA00000       /* sw reg,n($sp) */
                || (inst & 0xFFE00000) == 0xFFA00000)   /* sd reg,n($sp) */
               && (inst & 0x001F0000))  /* reg != $zero */
        continue;

      else if ((inst & 0xFFE00000) == 0xE7A00000)       /* swc1 freg,n($sp) */
        continue;
      else if ((inst & 0xF3E00000) == 0xA3C00000 && (inst & 0x001F0000))
        /* sx reg,n($s8) */
        continue;               /* reg != $zero */

      /* move $s8,$sp.  With different versions of gas this will be either
         `addu $s8,$sp,$zero' or `or $s8,$sp,$zero' or `daddu s8,sp,$0'.
         Accept any one of these.  */
      else if (inst == 0x03A0F021 || inst == 0x03a0f025 || inst == 0x03a0f02d)
        continue;

      else if ((inst & 0xFF9F07FF) == 0x00800021)       /* move reg,$a0-$a3 */
        continue;
      else if (high_word == 0x3c1c)     /* lui $gp,n */
        continue;
      else if (high_word == 0x279c)     /* addiu $gp,$gp,n */
        continue;
      else if (inst == 0x0399e021       /* addu $gp,$gp,$t9 */
               || inst == 0x033ce021)   /* addu $gp,$t9,$gp */
        continue;
      /* The following instructions load $at or $t0 with an immediate
         value in preparation for a stack adjustment via
         subu $sp,$sp,[$at,$t0]. These instructions could also initialize
         a local variable, so we accept them only before a stack adjustment
         instruction was seen.  */
      else if (!seen_sp_adjust)
        {
          if (high_word == 0x3c01 ||    /* lui $at,n */
              high_word == 0x3c08)      /* lui $t0,n */
            {
              load_immediate_bytes += MIPS_INSTLEN;     /* FIXME!! */
              continue;
            }
          else if (high_word == 0x3421 ||       /* ori $at,$at,n */
                   high_word == 0x3508 ||       /* ori $t0,$t0,n */
                   high_word == 0x3401 ||       /* ori $at,$zero,n */
                   high_word == 0x3408)         /* ori $t0,$zero,n */
            {
              load_immediate_bytes += MIPS_INSTLEN;     /* FIXME!! */
              continue;
            }
          else
            break;
        }
      else
        break;
    }

  /* In a frameless function, we might have incorrectly
     skipped some load immediate instructions. Undo the skipping
     if the load immediate was not followed by a stack adjustment.  */
  if (load_immediate_bytes && !seen_sp_adjust)
    pc -= load_immediate_bytes;
  return pc;
}

/* Skip the PC past function prologue instructions (16-bit version).
   This is a helper function for mips_skip_prologue.  */

static CORE_ADDR
mips16_skip_prologue (pc, lenient)
     CORE_ADDR pc;              /* starting PC to search from */
     int lenient;
{
  CORE_ADDR end_pc;
  int extend_bytes = 0;
  int prev_extend_bytes;

  /* Table of instructions likely to be found in a function prologue.  */
  static struct
    {
      unsigned short inst;
      unsigned short mask;
    }
  table[] =
  {
    {
      0x6300, 0xff00
    }
    ,                           /* addiu $sp,offset */
    {
      0xfb00, 0xff00
    }
    ,                           /* daddiu $sp,offset */
    {
      0xd000, 0xf800
    }
    ,                           /* sw reg,n($sp) */
    {
      0xf900, 0xff00
    }
    ,                           /* sd reg,n($sp) */
    {
      0x6200, 0xff00
    }
    ,                           /* sw $ra,n($sp) */
    {
      0xfa00, 0xff00
    }
    ,                           /* sd $ra,n($sp) */
    {
      0x673d, 0xffff
    }
    ,                           /* move $s1,sp */
    {
      0xd980, 0xff80
    }
    ,                           /* sw $a0-$a3,n($s1) */
    {
      0x6704, 0xff1c
    }
    ,                           /* move reg,$a0-$a3 */
    {
      0xe809, 0xf81f
    }
    ,                           /* entry pseudo-op */
    {
      0x0100, 0xff00
    }
    ,                           /* addiu $s1,$sp,n */
    {
      0, 0
    }                           /* end of table marker */
  };

  /* Skip the typical prologue instructions. These are the stack adjustment
     instruction and the instructions that save registers on the stack
     or in the gcc frame.  */
  for (end_pc = pc + 100; pc < end_pc; pc += MIPS16_INSTLEN)
    {
      unsigned short inst;
      int i;

      inst = mips_fetch_instruction (pc);

      /* Normally we ignore an extend instruction.  However, if it is
         not followed by a valid prologue instruction, we must adjust
         the pc back over the extend so that it won't be considered
         part of the prologue.  */
      if ((inst & 0xf800) == 0xf000)    /* extend */
        {
          extend_bytes = MIPS16_INSTLEN;
          continue;
        }
      prev_extend_bytes = extend_bytes;
      extend_bytes = 0;

      /* Check for other valid prologue instructions besides extend.  */
      for (i = 0; table[i].mask != 0; i++)
        if ((inst & table[i].mask) == table[i].inst)    /* found, get out */
          break;
      if (table[i].mask != 0)   /* it was in table? */
        continue;               /* ignore it */
      else
        /* non-prologue */
        {
          /* Return the current pc, adjusted backwards by 2 if
             the previous instruction was an extend.  */
          return pc - prev_extend_bytes;
        }
    }
  return pc;
}

/* To skip prologues, I use this predicate.  Returns either PC itself
   if the code at PC does not look like a function prologue; otherwise
   returns an address that (if we're lucky) follows the prologue.  If
   LENIENT, then we must skip everything which is involved in setting
   up the frame (it's OK to skip more, just so long as we don't skip
   anything which might clobber the registers which are being saved.
   We must skip more in the case where part of the prologue is in the
   delay slot of a non-prologue instruction).  */

CORE_ADDR
mips_skip_prologue (pc, lenient)
     CORE_ADDR pc;
     int lenient;
{
  /* See if we can determine the end of the prologue via the symbol table.
     If so, then return either PC, or the PC after the prologue, whichever
     is greater.  */

  CORE_ADDR post_prologue_pc = after_prologue (pc, NULL);

  if (post_prologue_pc != 0)
    return max (pc, post_prologue_pc);

  /* Can't determine prologue from the symbol table, need to examine
     instructions.  */

  if (pc_is_mips16 (pc))
    return mips16_skip_prologue (pc, lenient);
  else
    return mips32_skip_prologue (pc, lenient);
}

#if 0
/* The lenient prologue stuff should be superseded by the code in
   init_extra_frame_info which looks to see whether the stores mentioned
   in the proc_desc have actually taken place.  */

/* Is address PC in the prologue (loosely defined) for function at
   STARTADDR?  */

static int
mips_in_lenient_prologue (startaddr, pc)
     CORE_ADDR startaddr;
     CORE_ADDR pc;
{
  CORE_ADDR end_prologue = mips_skip_prologue (startaddr, 1);
  return pc >= startaddr && pc < end_prologue;
}
#endif

/* Determine how a return value is stored within the MIPS register
   file, given the return type `valtype'. */

struct return_value_word
{
  int len;
  int reg;
  int reg_offset;
  int buf_offset;
};

static void return_value_location PARAMS ((struct type *, struct return_value_word *, struct return_value_word *));

static void
return_value_location (valtype, hi, lo)
     struct type *valtype;
     struct return_value_word *hi;
     struct return_value_word *lo;
{
  int len = TYPE_LENGTH (valtype);

  if (TYPE_CODE (valtype) == TYPE_CODE_FLT
      && ((MIPS_FPU_TYPE == MIPS_FPU_DOUBLE && (len == 4 || len == 8))
          || (MIPS_FPU_TYPE == MIPS_FPU_SINGLE && len == 4)))
    {
      if (!FP_REGISTER_DOUBLE && len == 8)
        {
          /* We need to break a 64bit float in two 32 bit halves and
             spread them across a floating-point register pair. */
          lo->buf_offset = TARGET_BYTE_ORDER == BIG_ENDIAN ? 4 : 0;
          hi->buf_offset = TARGET_BYTE_ORDER == BIG_ENDIAN ? 0 : 4;
          lo->reg_offset = ((TARGET_BYTE_ORDER == BIG_ENDIAN
                             && REGISTER_RAW_SIZE (FP0_REGNUM) == 8)
                            ? 4 : 0);
          hi->reg_offset = lo->reg_offset;
          lo->reg = FP0_REGNUM + 0;
          hi->reg = FP0_REGNUM + 1;
          lo->len = 4;
          hi->len = 4;
        }
      else
        {
          /* The floating point value fits in a single floating-point
             register. */
          lo->reg_offset = ((TARGET_BYTE_ORDER == BIG_ENDIAN
                             && REGISTER_RAW_SIZE (FP0_REGNUM) == 8
                             && len == 4)
                            ? 4 : 0);
          lo->reg = FP0_REGNUM;
          lo->len = len;
          lo->buf_offset = 0;
          hi->len = 0;
          hi->reg_offset = 0;
          hi->buf_offset = 0;
          hi->reg = 0;
        }
    }
  else
    {
      /* Locate a result possibly spread across two registers. */
      int regnum = 2;
      lo->reg = regnum + 0;
      hi->reg = regnum + 1;
      if (TARGET_BYTE_ORDER == BIG_ENDIAN
          && len < MIPS_SAVED_REGSIZE)
        {
          /* "un-left-justify" the value in the low register */
          lo->reg_offset = MIPS_SAVED_REGSIZE - len;
          lo->len = len;
          hi->reg_offset = 0;
          hi->len = 0;
        }
      else if (TARGET_BYTE_ORDER == BIG_ENDIAN
               && len > MIPS_SAVED_REGSIZE      /* odd-size structs */
               && len < MIPS_SAVED_REGSIZE * 2
               && (TYPE_CODE (valtype) == TYPE_CODE_STRUCT ||
                   TYPE_CODE (valtype) == TYPE_CODE_UNION))
        {
          /* "un-left-justify" the value spread across two registers. */
          lo->reg_offset = 2 * MIPS_SAVED_REGSIZE - len;
          lo->len = MIPS_SAVED_REGSIZE - lo->reg_offset;
          hi->reg_offset = 0;
          hi->len = len - lo->len;
        }
      else
        {
          /* Only perform a partial copy of the second register. */
          lo->reg_offset = 0;
          hi->reg_offset = 0;
          if (len > MIPS_SAVED_REGSIZE)
            {
              lo->len = MIPS_SAVED_REGSIZE;
              hi->len = len - MIPS_SAVED_REGSIZE;
            }
          else
            {
              lo->len = len;
              hi->len = 0;
            }
        }
      if (TARGET_BYTE_ORDER == BIG_ENDIAN
          && REGISTER_RAW_SIZE (regnum) == 8
          && MIPS_SAVED_REGSIZE == 4)
        {
          /* Account for the fact that only the least-signficant part
             of the register is being used */
          lo->reg_offset += 4;
          hi->reg_offset += 4;
        }
      lo->buf_offset = 0;
      hi->buf_offset = lo->len;
    }
}

/* Given a return value in `regbuf' with a type `valtype', extract and
   copy its value into `valbuf'. */

void
mips_extract_return_value (valtype, regbuf, valbuf)
     struct type *valtype;
     char regbuf[REGISTER_BYTES];
     char *valbuf;
{
  struct return_value_word lo;
  struct return_value_word hi;
  return_value_location (valtype, &lo, &hi);

  memcpy (valbuf + lo.buf_offset,
          regbuf + REGISTER_BYTE (lo.reg) + lo.reg_offset,
          lo.len);

  if (hi.len > 0)
    memcpy (valbuf + hi.buf_offset,
            regbuf + REGISTER_BYTE (hi.reg) + hi.reg_offset,
            hi.len);

#if 0
  int regnum;
  int offset = 0;
  int len = TYPE_LENGTH (valtype);

  regnum = 2;
  if (TYPE_CODE (valtype) == TYPE_CODE_FLT
      && (MIPS_FPU_TYPE == MIPS_FPU_DOUBLE
          || (MIPS_FPU_TYPE == MIPS_FPU_SINGLE
              && len <= MIPS_FPU_SINGLE_REGSIZE)))
    regnum = FP0_REGNUM;

  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    {                           /* "un-left-justify" the value from the register */
      if (len < REGISTER_RAW_SIZE (regnum))
        offset = REGISTER_RAW_SIZE (regnum) - len;
      if (len > REGISTER_RAW_SIZE (regnum) &&   /* odd-size structs */
          len < REGISTER_RAW_SIZE (regnum) * 2 &&
          (TYPE_CODE (valtype) == TYPE_CODE_STRUCT ||
           TYPE_CODE (valtype) == TYPE_CODE_UNION))
        offset = 2 * REGISTER_RAW_SIZE (regnum) - len;
    }
  memcpy (valbuf, regbuf + REGISTER_BYTE (regnum) + offset, len);
  REGISTER_CONVERT_TO_TYPE (regnum, valtype, valbuf);
#endif
}

/* Given a return value in `valbuf' with a type `valtype', write it's
   value into the appropriate register. */

void
mips_store_return_value (valtype, valbuf)
     struct type *valtype;
     char *valbuf;
{
  char raw_buffer[MAX_REGISTER_RAW_SIZE];
  struct return_value_word lo;
  struct return_value_word hi;
  return_value_location (valtype, &lo, &hi);

  memset (raw_buffer, 0, sizeof (raw_buffer));
  memcpy (raw_buffer + lo.reg_offset, valbuf + lo.buf_offset, lo.len);
  write_register_bytes (REGISTER_BYTE (lo.reg),
                        raw_buffer,
                        REGISTER_RAW_SIZE (lo.reg));

  if (hi.len > 0)
    {
      memset (raw_buffer, 0, sizeof (raw_buffer));
      memcpy (raw_buffer + hi.reg_offset, valbuf + hi.buf_offset, hi.len);
      write_register_bytes (REGISTER_BYTE (hi.reg),
                            raw_buffer,
                            REGISTER_RAW_SIZE (hi.reg));
    }

#if 0
  int regnum;
  int offset = 0;
  int len = TYPE_LENGTH (valtype);
  char raw_buffer[MAX_REGISTER_RAW_SIZE];

  regnum = 2;
  if (TYPE_CODE (valtype) == TYPE_CODE_FLT
      && (MIPS_FPU_TYPE == MIPS_FPU_DOUBLE
          || (MIPS_FPU_TYPE == MIPS_FPU_SINGLE
              && len <= MIPS_REGSIZE)))
    regnum = FP0_REGNUM;

  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    {                           /* "left-justify" the value in the register */
      if (len < REGISTER_RAW_SIZE (regnum))
        offset = REGISTER_RAW_SIZE (regnum) - len;
      if (len > REGISTER_RAW_SIZE (regnum) &&   /* odd-size structs */
          len < REGISTER_RAW_SIZE (regnum) * 2 &&
          (TYPE_CODE (valtype) == TYPE_CODE_STRUCT ||
           TYPE_CODE (valtype) == TYPE_CODE_UNION))
        offset = 2 * REGISTER_RAW_SIZE (regnum) - len;
    }
  memcpy (raw_buffer + offset, valbuf, len);
  REGISTER_CONVERT_FROM_TYPE (regnum, valtype, raw_buffer);
  write_register_bytes (REGISTER_BYTE (regnum), raw_buffer,
                        len > REGISTER_RAW_SIZE (regnum) ?
                        len : REGISTER_RAW_SIZE (regnum));
#endif
}

/* Exported procedure: Is PC in the signal trampoline code */

int
in_sigtramp (pc, ignore)
     CORE_ADDR pc;
     char *ignore;              /* function name */
{
  if (sigtramp_address == 0)
    fixup_sigtramp ();
  return (pc >= sigtramp_address && pc < sigtramp_end);
}

/* Commands to show/set the MIPS FPU type.  */

static void show_mipsfpu_command PARAMS ((char *, int));
static void
show_mipsfpu_command (args, from_tty)
     char *args;
     int from_tty;
{
  char *msg;
  char *fpu;
  switch (MIPS_FPU_TYPE)
    {
    case MIPS_FPU_SINGLE:
      fpu = "single-precision";
      break;
    case MIPS_FPU_DOUBLE:
      fpu = "double-precision";
      break;
    case MIPS_FPU_NONE:
      fpu = "absent (none)";
      break;
    }
  if (mips_fpu_type_auto)
    printf_unfiltered ("The MIPS floating-point coprocessor is set automatically (currently %s)\n",
                       fpu);
  else
    printf_unfiltered ("The MIPS floating-point coprocessor is assumed to be %s\n",
                       fpu);
}


static void set_mipsfpu_command PARAMS ((char *, int));
static void
set_mipsfpu_command (args, from_tty)
     char *args;
     int from_tty;
{
  printf_unfiltered ("\"set mipsfpu\" must be followed by \"double\", \"single\",\"none\" or \"auto\".\n");
  show_mipsfpu_command (args, from_tty);
}

static void set_mipsfpu_single_command PARAMS ((char *, int));
static void
set_mipsfpu_single_command (args, from_tty)
     char *args;
     int from_tty;
{
  mips_fpu_type = MIPS_FPU_SINGLE;
  mips_fpu_type_auto = 0;
}

static void set_mipsfpu_double_command PARAMS ((char *, int));
static void
set_mipsfpu_double_command (args, from_tty)
     char *args;
     int from_tty;
{
  mips_fpu_type = MIPS_FPU_DOUBLE;
  mips_fpu_type_auto = 0;
}

static void set_mipsfpu_none_command PARAMS ((char *, int));
static void
set_mipsfpu_none_command (args, from_tty)
     char *args;
     int from_tty;
{
  mips_fpu_type = MIPS_FPU_NONE;
  mips_fpu_type_auto = 0;
}

static void set_mipsfpu_auto_command PARAMS ((char *, int));
static void
set_mipsfpu_auto_command (args, from_tty)
     char *args;
     int from_tty;
{
  mips_fpu_type_auto = 1;
}

/* Command to set the processor type.  */

void
mips_set_processor_type_command (args, from_tty)
     char *args;
     int from_tty;
{
  int i;

  if (tmp_mips_processor_type == NULL || *tmp_mips_processor_type == '\0')
    {
      printf_unfiltered ("The known MIPS processor types are as follows:\n\n");
      for (i = 0; mips_processor_type_table[i].name != NULL; ++i)
        printf_unfiltered ("%s\n", mips_processor_type_table[i].name);

      /* Restore the value.  */
      tmp_mips_processor_type = strsave (mips_processor_type);

      return;
    }

  if (!mips_set_processor_type (tmp_mips_processor_type))
    {
      error ("Unknown processor type `%s'.", tmp_mips_processor_type);
      /* Restore its value.  */
      tmp_mips_processor_type = strsave (mips_processor_type);
    }
}

static void
mips_show_processor_type_command (args, from_tty)
     char *args;
     int from_tty;
{
}

/* Modify the actual processor type. */

int
mips_set_processor_type (str)
     char *str;
{
  int i, j;

  if (str == NULL)
    return 0;

  for (i = 0; mips_processor_type_table[i].name != NULL; ++i)
    {
      if (strcasecmp (str, mips_processor_type_table[i].name) == 0)
        {
          mips_processor_type = str;
          mips_processor_reg_names = mips_processor_type_table[i].regnames;
          return 1;
          /* FIXME tweak fpu flag too */
        }
    }

  return 0;
}

/* Attempt to identify the particular processor model by reading the
   processor id.  */

char *
mips_read_processor_type ()
{
  CORE_ADDR prid;

  prid = read_register (PRID_REGNUM);

  if ((prid & ~0xf) == 0x700)
    return savestring ("r3041", strlen ("r3041"));

  return NULL;
}

/* Just like reinit_frame_cache, but with the right arguments to be
   callable as an sfunc.  */

static void
reinit_frame_cache_sfunc (args, from_tty, c)
     char *args;
     int from_tty;
     struct cmd_list_element *c;
{
  reinit_frame_cache ();
}

int
gdb_print_insn_mips (memaddr, info)
     bfd_vma memaddr;
     disassemble_info *info;
{
  mips_extra_func_info_t proc_desc;

  /* Search for the function containing this address.  Set the low bit
     of the address when searching, in case we were given an even address
     that is the start of a 16-bit function.  If we didn't do this,
     the search would fail because the symbol table says the function
     starts at an odd address, i.e. 1 byte past the given address.  */
  memaddr = ADDR_BITS_REMOVE (memaddr);
  proc_desc = non_heuristic_proc_desc (MAKE_MIPS16_ADDR (memaddr), NULL);

  /* Make an attempt to determine if this is a 16-bit function.  If
     the procedure descriptor exists and the address therein is odd,
     it's definitely a 16-bit function.  Otherwise, we have to just
     guess that if the address passed in is odd, it's 16-bits.  */
  if (proc_desc)
    info->mach = pc_is_mips16 (PROC_LOW_ADDR (proc_desc)) ? 16 : TM_PRINT_INSN_MACH;
  else
    info->mach = pc_is_mips16 (memaddr) ? 16 : TM_PRINT_INSN_MACH;

  /* Round down the instruction address to the appropriate boundary.  */
  memaddr &= (info->mach == 16 ? ~1 : ~3);

  /* Call the appropriate disassembler based on the target endian-ness.  */
  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    return print_insn_big_mips (memaddr, info);
  else
    return print_insn_little_mips (memaddr, info);
}

/* Old-style breakpoint macros.
   The IDT board uses an unusual breakpoint value, and sometimes gets
   confused when it sees the usual MIPS breakpoint instruction.  */

#define BIG_BREAKPOINT {0, 0x5, 0, 0xd}
#define LITTLE_BREAKPOINT {0xd, 0, 0x5, 0}
#define PMON_BIG_BREAKPOINT {0, 0, 0, 0xd}
#define PMON_LITTLE_BREAKPOINT {0xd, 0, 0, 0}
#define IDT_BIG_BREAKPOINT {0, 0, 0x0a, 0xd}
#define IDT_LITTLE_BREAKPOINT {0xd, 0x0a, 0, 0}
#define MIPS16_BIG_BREAKPOINT {0xe8, 0xa5}
#define MIPS16_LITTLE_BREAKPOINT {0xa5, 0xe8}

/* This function implements the BREAKPOINT_FROM_PC macro.  It uses the program
   counter value to determine whether a 16- or 32-bit breakpoint should be
   used.  It returns a pointer to a string of bytes that encode a breakpoint
   instruction, stores the length of the string to *lenptr, and adjusts pc
   (if necessary) to point to the actual memory location where the
   breakpoint should be inserted.  */

unsigned char *
mips_breakpoint_from_pc (pcptr, lenptr)
     CORE_ADDR *pcptr;
     int *lenptr;
{
  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    {
      if (pc_is_mips16 (*pcptr))
        {
          static char mips16_big_breakpoint[] = MIPS16_BIG_BREAKPOINT;
          *pcptr = UNMAKE_MIPS16_ADDR (*pcptr);
          *lenptr = sizeof (mips16_big_breakpoint);
          return mips16_big_breakpoint;
        }
      else
        {
          static char big_breakpoint[] = BIG_BREAKPOINT;
          static char pmon_big_breakpoint[] = PMON_BIG_BREAKPOINT;
          static char idt_big_breakpoint[] = IDT_BIG_BREAKPOINT;

          *lenptr = sizeof (big_breakpoint);

          if (strcmp (target_shortname, "mips") == 0)
            return idt_big_breakpoint;
          else if (strcmp (target_shortname, "ddb") == 0
                   || strcmp (target_shortname, "pmon") == 0
                   || strcmp (target_shortname, "lsi") == 0)
            return pmon_big_breakpoint;
          else
            return big_breakpoint;
        }
    }
  else
    {
      if (pc_is_mips16 (*pcptr))
        {
          static char mips16_little_breakpoint[] = MIPS16_LITTLE_BREAKPOINT;
          *pcptr = UNMAKE_MIPS16_ADDR (*pcptr);
          *lenptr = sizeof (mips16_little_breakpoint);
          return mips16_little_breakpoint;
        }
      else
        {
          static char little_breakpoint[] = LITTLE_BREAKPOINT;
          static char pmon_little_breakpoint[] = PMON_LITTLE_BREAKPOINT;
          static char idt_little_breakpoint[] = IDT_LITTLE_BREAKPOINT;

          *lenptr = sizeof (little_breakpoint);

          if (strcmp (target_shortname, "mips") == 0)
            return idt_little_breakpoint;
          else if (strcmp (target_shortname, "ddb") == 0
                   || strcmp (target_shortname, "pmon") == 0
                   || strcmp (target_shortname, "lsi") == 0)
            return pmon_little_breakpoint;
          else
            return little_breakpoint;
        }
    }
}

/* If PC is in a mips16 call or return stub, return the address of the target
   PC, which is either the callee or the caller.  There are several
   cases which must be handled:

   * If the PC is in __mips16_ret_{d,s}f, this is a return stub and the
   target PC is in $31 ($ra).
   * If the PC is in __mips16_call_stub_{1..10}, this is a call stub
   and the target PC is in $2.
   * If the PC at the start of __mips16_call_stub_{s,d}f_{0..10}, i.e.
   before the jal instruction, this is effectively a call stub
   and the the target PC is in $2.  Otherwise this is effectively
   a return stub and the target PC is in $18.

   See the source code for the stubs in gcc/config/mips/mips16.S for
   gory details.

   This function implements the SKIP_TRAMPOLINE_CODE macro.
 */

CORE_ADDR
mips_skip_stub (pc)
     CORE_ADDR pc;
{
  char *name;
  CORE_ADDR start_addr;

  /* Find the starting address and name of the function containing the PC.  */
  if (find_pc_partial_function (pc, &name, &start_addr, NULL) == 0)
    return 0;

  /* If the PC is in __mips16_ret_{d,s}f, this is a return stub and the
     target PC is in $31 ($ra).  */
  if (strcmp (name, "__mips16_ret_sf") == 0
      || strcmp (name, "__mips16_ret_df") == 0)
    return read_register (RA_REGNUM);

  if (strncmp (name, "__mips16_call_stub_", 19) == 0)
    {
      /* If the PC is in __mips16_call_stub_{1..10}, this is a call stub
         and the target PC is in $2.  */
      if (name[19] >= '0' && name[19] <= '9')
        return read_register (2);

      /* If the PC at the start of __mips16_call_stub_{s,d}f_{0..10}, i.e.
         before the jal instruction, this is effectively a call stub
         and the the target PC is in $2.  Otherwise this is effectively
         a return stub and the target PC is in $18.  */
      else if (name[19] == 's' || name[19] == 'd')
        {
          if (pc == start_addr)
            {
              /* Check if the target of the stub is a compiler-generated
                 stub.  Such a stub for a function bar might have a name
                 like __fn_stub_bar, and might look like this:
                 mfc1    $4,$f13
                 mfc1    $5,$f12
                 mfc1    $6,$f15
                 mfc1    $7,$f14
                 la      $1,bar   (becomes a lui/addiu pair)
                 jr      $1
                 So scan down to the lui/addi and extract the target
                 address from those two instructions.  */

              CORE_ADDR target_pc = read_register (2);
              t_inst inst;
              int i;

              /* See if the name of the target function is  __fn_stub_*.  */
              if (find_pc_partial_function (target_pc, &name, NULL, NULL) == 0)
                return target_pc;
              if (strncmp (name, "__fn_stub_", 10) != 0
                  && strcmp (name, "etext") != 0
                  && strcmp (name, "_etext") != 0)
                return target_pc;

              /* Scan through this _fn_stub_ code for the lui/addiu pair.
                 The limit on the search is arbitrarily set to 20
                 instructions.  FIXME.  */
              for (i = 0, pc = 0; i < 20; i++, target_pc += MIPS_INSTLEN)
                {
                  inst = mips_fetch_instruction (target_pc);
                  if ((inst & 0xffff0000) == 0x3c010000)        /* lui $at */
                    pc = (inst << 16) & 0xffff0000;     /* high word */
                  else if ((inst & 0xffff0000) == 0x24210000)   /* addiu $at */
                    return pc | (inst & 0xffff);        /* low word */
                }

              /* Couldn't find the lui/addui pair, so return stub address.  */
              return target_pc;
            }
          else
            /* This is the 'return' part of a call stub.  The return
               address is in $r18.  */
            return read_register (18);
        }
    }
  return 0;                     /* not a stub */
}


/* Return non-zero if the PC is inside a call thunk (aka stub or trampoline).
   This implements the IN_SOLIB_CALL_TRAMPOLINE macro.  */

int
mips_in_call_stub (pc, name)
     CORE_ADDR pc;
     char *name;
{
  CORE_ADDR start_addr;

  /* Find the starting address of the function containing the PC.  If the
     caller didn't give us a name, look it up at the same time.  */
  if (find_pc_partial_function (pc, name ? NULL : &name, &start_addr, NULL) == 0)
    return 0;

  if (strncmp (name, "__mips16_call_stub_", 19) == 0)
    {
      /* If the PC is in __mips16_call_stub_{1..10}, this is a call stub.  */
      if (name[19] >= '0' && name[19] <= '9')
        return 1;
      /* If the PC at the start of __mips16_call_stub_{s,d}f_{0..10}, i.e.
         before the jal instruction, this is effectively a call stub.  */
      else if (name[19] == 's' || name[19] == 'd')
        return pc == start_addr;
    }

  return 0;                     /* not a stub */
}


/* Return non-zero if the PC is inside a return thunk (aka stub or trampoline).
   This implements the IN_SOLIB_RETURN_TRAMPOLINE macro.  */

int
mips_in_return_stub (pc, name)
     CORE_ADDR pc;
     char *name;
{
  CORE_ADDR start_addr;

  /* Find the starting address of the function containing the PC.  */
  if (find_pc_partial_function (pc, NULL, &start_addr, NULL) == 0)
    return 0;

  /* If the PC is in __mips16_ret_{d,s}f, this is a return stub.  */
  if (strcmp (name, "__mips16_ret_sf") == 0
      || strcmp (name, "__mips16_ret_df") == 0)
    return 1;

  /* If the PC is in __mips16_call_stub_{s,d}f_{0..10} but not at the start,
     i.e. after the jal instruction, this is effectively a return stub.  */
  if (strncmp (name, "__mips16_call_stub_", 19) == 0
      && (name[19] == 's' || name[19] == 'd')
      && pc != start_addr)
    return 1;

  return 0;                     /* not a stub */
}


/* Return non-zero if the PC is in a library helper function that should
   be ignored.  This implements the IGNORE_HELPER_CALL macro.  */

int
mips_ignore_helper (pc)
     CORE_ADDR pc;
{
  char *name;

  /* Find the starting address and name of the function containing the PC.  */
  if (find_pc_partial_function (pc, &name, NULL, NULL) == 0)
    return 0;

  /* If the PC is in __mips16_ret_{d,s}f, this is a library helper function
     that we want to ignore.  */
  return (strcmp (name, "__mips16_ret_sf") == 0
          || strcmp (name, "__mips16_ret_df") == 0);
}


/* Return a location where we can set a breakpoint that will be hit
   when an inferior function call returns.  This is normally the
   program's entry point.  Executables that don't have an entry
   point (e.g. programs in ROM) should define a symbol __CALL_DUMMY_ADDRESS
   whose address is the location where the breakpoint should be placed.  */

CORE_ADDR
mips_call_dummy_address ()
{
  struct minimal_symbol *sym;

  sym = lookup_minimal_symbol ("__CALL_DUMMY_ADDRESS", NULL, NULL);
  if (sym)
    return SYMBOL_VALUE_ADDRESS (sym);
  else
    return entry_point_address ();
}


void
_initialize_mips_tdep ()
{
  static struct cmd_list_element *mipsfpulist = NULL;
  struct cmd_list_element *c;

  if (!tm_print_insn)           /* Someone may have already set it */
    tm_print_insn = gdb_print_insn_mips;

  /* Let the user turn off floating point and set the fence post for
     heuristic_proc_start.  */

  add_prefix_cmd ("mipsfpu", class_support, set_mipsfpu_command,
                  "Set use of MIPS floating-point coprocessor.",
                  &mipsfpulist, "set mipsfpu ", 0, &setlist);
  add_cmd ("single", class_support, set_mipsfpu_single_command,
           "Select single-precision MIPS floating-point coprocessor.",
           &mipsfpulist);
  add_cmd ("double", class_support, set_mipsfpu_double_command,
           "Select double-precision MIPS floating-point coprocessor .",
           &mipsfpulist);
  add_alias_cmd ("on", "double", class_support, 1, &mipsfpulist);
  add_alias_cmd ("yes", "double", class_support, 1, &mipsfpulist);
  add_alias_cmd ("1", "double", class_support, 1, &mipsfpulist);
  add_cmd ("none", class_support, set_mipsfpu_none_command,
           "Select no MIPS floating-point coprocessor.",
           &mipsfpulist);
  add_alias_cmd ("off", "none", class_support, 1, &mipsfpulist);
  add_alias_cmd ("no", "none", class_support, 1, &mipsfpulist);
  add_alias_cmd ("0", "none", class_support, 1, &mipsfpulist);
  add_cmd ("auto", class_support, set_mipsfpu_auto_command,
           "Select MIPS floating-point coprocessor automatically.",
           &mipsfpulist);
  add_cmd ("mipsfpu", class_support, show_mipsfpu_command,
           "Show current use of MIPS floating-point coprocessor target.",
           &showlist);

  c = add_set_cmd ("processor", class_support, var_string_noescape,
                   (char *) &tmp_mips_processor_type,
                   "Set the type of MIPS processor in use.\n\
Set this to be able to access processor-type-specific registers.\n\
",
                   &setlist);
  c->function.cfunc = mips_set_processor_type_command;
  c = add_show_from_set (c, &showlist);
  c->function.cfunc = mips_show_processor_type_command;

  tmp_mips_processor_type = strsave (DEFAULT_MIPS_TYPE);
  mips_set_processor_type_command (strsave (DEFAULT_MIPS_TYPE), 0);

  /* We really would like to have both "0" and "unlimited" work, but
     command.c doesn't deal with that.  So make it a var_zinteger
     because the user can always use "999999" or some such for unlimited.  */
  c = add_set_cmd ("heuristic-fence-post", class_support, var_zinteger,
                   (char *) &heuristic_fence_post,
                   "\
Set the distance searched for the start of a function.\n\
If you are debugging a stripped executable, GDB needs to search through the\n\
program for the start of a function.  This command sets the distance of the\n\
search.  The only need to set it is when debugging a stripped executable.",
                   &setlist);
  /* We need to throw away the frame cache when we set this, since it
     might change our ability to get backtraces.  */
  c->function.sfunc = reinit_frame_cache_sfunc;
  add_show_from_set (c, &showlist);

  /* Allow the user to control whether the upper bits of 64-bit
     addresses should be zeroed.  */
  add_show_from_set
    (add_set_cmd ("mask-address", no_class, var_boolean, (char *) &mask_address_p,
                  "Set zeroing of upper 32 bits of 64-bit addresses.\n\
Use \"on\" to enable the masking, and \"off\" to disable it.\n\
Without an argument, zeroing of upper address bits is enabled.", &setlist),
     &showlist);

  /* Allow the user to control the size of 32 bit registers within the
     raw remote packet.  */
  add_show_from_set (add_set_cmd ("remote-mips64-transfers-32bit-regs",
                                  class_obscure,
                                  var_boolean,
                                  (char *)&mips64_transfers_32bit_regs_p, "\
Set compatibility with MIPS targets that transfers 32 and 64 bit quantities.\n\
Use \"on\" to enable backward compatibility with older MIPS 64 GDB+target\n\
that would transfer 32 bits for some registers (e.g. SR, FSR) and\n\
64 bits for others.  Use \"off\" to disable compatibility mode",
                                  &setlist),
                     &showlist);
}