path: root/gcc/config/pdp11/pdp11.cc

/* Subroutines for gcc2 for pdp11.
   Copyright (C) 1994-2023 Free Software Foundation, Inc.
   Contributed by Michael K. Gschwind (mike@vlsivie.tuwien.ac.at).

This file is part of GCC.

GCC 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 3, or (at your option)
any later version.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#define IN_TARGET_CODE 1

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "stringpool.h"
#include "attribs.h"
#include "df.h"
#include "memmodel.h"
#include "tm_p.h"
#include "insn-config.h"
#include "insn-attr.h"
#include "regs.h"
#include "emit-rtl.h"
#include "recog.h"
#include "conditions.h"
#include "output.h"
#include "stor-layout.h"
#include "varasm.h"
#include "calls.h"
#include "expr.h"
#include "builtins.h"
#include "explow.h"
#include "expmed.h"

/* This file should be included last.  */
#include "target-def.h"

/* this is the current value returned by the macro FIRST_PARM_OFFSET 
   defined in tm.h */
int current_first_parm_offset;

/* Routines to encode/decode pdp11 floats */
static void encode_pdp11_f (const struct real_format *fmt,
			    long *, const REAL_VALUE_TYPE *);
static void decode_pdp11_f (const struct real_format *,
			    REAL_VALUE_TYPE *, const long *);
static void encode_pdp11_d (const struct real_format *fmt,
			    long *, const REAL_VALUE_TYPE *);
static void decode_pdp11_d (const struct real_format *,
			    REAL_VALUE_TYPE *, const long *);

/* These two are taken from the corresponding vax descriptors
   in real.cc, changing only the encode/decode routine pointers.  */
const struct real_format pdp11_f_format =
  {
    encode_pdp11_f,
    decode_pdp11_f,
    2,
    24,
    24,
    -127,
    127,
    15,
    15,
    0,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    "pdp11_f"
  };

const struct real_format pdp11_d_format =
  {
    encode_pdp11_d,
    decode_pdp11_d,
    2,
    56,
    56,
    -127,
    127,
    15,
    15,
    0,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    "pdp11_d"
  };

static void
encode_pdp11_f (const struct real_format *fmt ATTRIBUTE_UNUSED, long *buf,
		const REAL_VALUE_TYPE *r)
{
  (*vax_f_format.encode) (fmt, buf, r);
  buf[0] = ((buf[0] >> 16) & 0xffff) | ((buf[0] & 0xffff) << 16);
}

static void
decode_pdp11_f (const struct real_format *fmt ATTRIBUTE_UNUSED,
		REAL_VALUE_TYPE *r, const long *buf)
{
  long tbuf;
  tbuf = ((buf[0] >> 16) & 0xffff) | ((buf[0] & 0xffff) << 16);
  (*vax_f_format.decode) (fmt, r, &tbuf);
}

static void
encode_pdp11_d (const struct real_format *fmt ATTRIBUTE_UNUSED, long *buf,
		const REAL_VALUE_TYPE *r)
{
  (*vax_d_format.encode) (fmt, buf, r);
  buf[0] = ((buf[0] >> 16) & 0xffff) | ((buf[0] & 0xffff) << 16);
  buf[1] = ((buf[1] >> 16) & 0xffff) | ((buf[1] & 0xffff) << 16);
}

static void
decode_pdp11_d (const struct real_format *fmt ATTRIBUTE_UNUSED,
		REAL_VALUE_TYPE *r, const long *buf)
{
  long tbuf[2];
  tbuf[0] = ((buf[0] >> 16) & 0xffff) | ((buf[0] & 0xffff) << 16);
  tbuf[1] = ((buf[1] >> 16) & 0xffff) | ((buf[1] & 0xffff) << 16);
  (*vax_d_format.decode) (fmt, r, tbuf);
}

static const char *singlemove_string (rtx *);
static bool pdp11_assemble_integer (rtx, unsigned int, int);
static bool pdp11_rtx_costs (rtx, machine_mode, int, int, int *, bool);
static int pdp11_addr_cost (rtx, machine_mode, addr_space_t, bool);
static int pdp11_insn_cost (rtx_insn *insn, bool speed);
static rtx_insn *pdp11_md_asm_adjust (vec<rtx> &, vec<rtx> &,
				      vec<machine_mode> &, vec<const char *> &,
				      vec<rtx> &, HARD_REG_SET &, location_t);
static bool pdp11_return_in_memory (const_tree, const_tree);
static rtx pdp11_function_value (const_tree, const_tree, bool);
static rtx pdp11_libcall_value (machine_mode, const_rtx);
static bool pdp11_function_value_regno_p (const unsigned int);
static void pdp11_trampoline_init (rtx, tree, rtx);
static rtx pdp11_function_arg (cumulative_args_t, const function_arg_info &);
static void pdp11_function_arg_advance (cumulative_args_t,
					const function_arg_info &);
static void pdp11_conditional_register_usage (void);
static bool pdp11_legitimate_constant_p (machine_mode, rtx);

static bool pdp11_scalar_mode_supported_p (scalar_mode);

/* Initialize the GCC target structure.  */
#undef TARGET_ASM_BYTE_OP
#define TARGET_ASM_BYTE_OP NULL
#undef TARGET_ASM_ALIGNED_HI_OP
#define TARGET_ASM_ALIGNED_HI_OP NULL
#undef TARGET_ASM_ALIGNED_SI_OP
#define TARGET_ASM_ALIGNED_SI_OP NULL
#undef TARGET_ASM_INTEGER
#define TARGET_ASM_INTEGER pdp11_assemble_integer

/* These two apply to Unix and GNU assembler; for DEC, they are
   overridden during option processing.  */
#undef TARGET_ASM_OPEN_PAREN
#define TARGET_ASM_OPEN_PAREN "["
#undef TARGET_ASM_CLOSE_PAREN
#define TARGET_ASM_CLOSE_PAREN "]"

#undef TARGET_RTX_COSTS
#define TARGET_RTX_COSTS pdp11_rtx_costs

#undef  TARGET_ADDRESS_COST
#define TARGET_ADDRESS_COST pdp11_addr_cost

#undef  TARGET_INSN_COST
#define TARGET_INSN_COST pdp11_insn_cost

#undef  TARGET_MD_ASM_ADJUST
#define TARGET_MD_ASM_ADJUST pdp11_md_asm_adjust

#undef TARGET_FUNCTION_ARG
#define TARGET_FUNCTION_ARG pdp11_function_arg
#undef TARGET_FUNCTION_ARG_ADVANCE
#define TARGET_FUNCTION_ARG_ADVANCE pdp11_function_arg_advance

#undef TARGET_RETURN_IN_MEMORY
#define TARGET_RETURN_IN_MEMORY pdp11_return_in_memory

#undef TARGET_FUNCTION_VALUE
#define TARGET_FUNCTION_VALUE pdp11_function_value
#undef TARGET_LIBCALL_VALUE
#define TARGET_LIBCALL_VALUE pdp11_libcall_value
#undef TARGET_FUNCTION_VALUE_REGNO_P
#define TARGET_FUNCTION_VALUE_REGNO_P pdp11_function_value_regno_p

#undef TARGET_TRAMPOLINE_INIT
#define TARGET_TRAMPOLINE_INIT pdp11_trampoline_init

#undef  TARGET_SECONDARY_RELOAD
#define TARGET_SECONDARY_RELOAD pdp11_secondary_reload

#undef  TARGET_REGISTER_MOVE_COST 
#define TARGET_REGISTER_MOVE_COST pdp11_register_move_cost

#undef  TARGET_PREFERRED_RELOAD_CLASS
#define TARGET_PREFERRED_RELOAD_CLASS pdp11_preferred_reload_class

#undef  TARGET_PREFERRED_OUTPUT_RELOAD_CLASS
#define TARGET_PREFERRED_OUTPUT_RELOAD_CLASS pdp11_preferred_output_reload_class

#undef  TARGET_LRA_P
#define TARGET_LRA_P pdp11_lra_p

#undef  TARGET_LEGITIMATE_ADDRESS_P
#define TARGET_LEGITIMATE_ADDRESS_P pdp11_legitimate_address_p

#undef  TARGET_CONDITIONAL_REGISTER_USAGE
#define TARGET_CONDITIONAL_REGISTER_USAGE pdp11_conditional_register_usage

#undef  TARGET_OPTION_OVERRIDE
#define TARGET_OPTION_OVERRIDE pdp11_option_override

#undef  TARGET_ASM_FILE_START_FILE_DIRECTIVE
#define TARGET_ASM_FILE_START_FILE_DIRECTIVE true

#undef  TARGET_ASM_OUTPUT_IDENT
#define TARGET_ASM_OUTPUT_IDENT pdp11_output_ident

#undef  TARGET_ASM_FUNCTION_SECTION
#define TARGET_ASM_FUNCTION_SECTION pdp11_function_section

#undef  TARGET_ASM_NAMED_SECTION
#define	TARGET_ASM_NAMED_SECTION pdp11_asm_named_section

#undef  TARGET_ASM_INIT_SECTIONS
#define TARGET_ASM_INIT_SECTIONS pdp11_asm_init_sections

#undef  TARGET_ASM_FILE_START
#define TARGET_ASM_FILE_START pdp11_file_start

#undef  TARGET_ASM_FILE_END
#define TARGET_ASM_FILE_END pdp11_file_end

#undef  TARGET_PRINT_OPERAND
#define TARGET_PRINT_OPERAND pdp11_asm_print_operand

#undef  TARGET_PRINT_OPERAND_PUNCT_VALID_P
#define TARGET_PRINT_OPERAND_PUNCT_VALID_P pdp11_asm_print_operand_punct_valid_p

#undef  TARGET_LEGITIMATE_CONSTANT_P
#define TARGET_LEGITIMATE_CONSTANT_P pdp11_legitimate_constant_p

#undef  TARGET_SCALAR_MODE_SUPPORTED_P
#define TARGET_SCALAR_MODE_SUPPORTED_P pdp11_scalar_mode_supported_p

#undef  TARGET_HARD_REGNO_NREGS
#define TARGET_HARD_REGNO_NREGS pdp11_hard_regno_nregs

#undef  TARGET_HARD_REGNO_MODE_OK
#define TARGET_HARD_REGNO_MODE_OK pdp11_hard_regno_mode_ok

#undef  TARGET_MODES_TIEABLE_P
#define TARGET_MODES_TIEABLE_P pdp11_modes_tieable_p

#undef  TARGET_SECONDARY_MEMORY_NEEDED
#define TARGET_SECONDARY_MEMORY_NEEDED pdp11_secondary_memory_needed

#undef  TARGET_CAN_CHANGE_MODE_CLASS
#define TARGET_CAN_CHANGE_MODE_CLASS pdp11_can_change_mode_class

#undef TARGET_INVALID_WITHIN_DOLOOP
#define TARGET_INVALID_WITHIN_DOLOOP hook_constcharptr_const_rtx_insn_null

#undef  TARGET_CXX_GUARD_TYPE
#define TARGET_CXX_GUARD_TYPE pdp11_guard_type

#undef  TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT
#define TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT hook_bool_void_false

#undef  TARGET_CXX_LIBRARY_RTTI_COMDAT
#define TARGET_CXX_LIBRARY_RTTI_COMDAT hook_bool_void_false

#undef TARGET_HAVE_SPECULATION_SAFE_VALUE
#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed

#undef  TARGET_STACK_PROTECT_RUNTIME_ENABLED_P
#define TARGET_STACK_PROTECT_RUNTIME_ENABLED_P hook_bool_void_false

/* A helper function to determine if REGNO should be saved in the
   current function's stack frame.  */

static inline bool
pdp11_saved_regno (unsigned regno)
{
  return !call_used_or_fixed_reg_p (regno) && df_regs_ever_live_p (regno);
}

/* Expand the function prologue.  */

/* Frame layout, from high to low memory (stack push order):
   return address (from jsr instruction)
   saved CPU registers, lowest number first
   saved FPU registers, lowest number first, always 64 bit mode
   *** frame pointer points here ***
   local variables
   alloca storage if any.  */
void
pdp11_expand_prologue (void)
{							       
  HOST_WIDE_INT fsize = get_frame_size ();
  unsigned regno;
  rtx x, via_ac = NULL;

  /* If we are outputting code for main, the switch FPU to the
     right mode if TARGET_FPU.  */
  if (MAIN_NAME_P (DECL_NAME (current_function_decl)) && TARGET_FPU)
    {
      emit_insn (gen_setd ());
      emit_insn (gen_seti ());
    }
    
  /* Save CPU registers.  */
  for (regno = R0_REGNUM; regno <= PC_REGNUM; regno++)
    if (pdp11_saved_regno (regno))
      {
	x = gen_rtx_PRE_DEC (Pmode, stack_pointer_rtx);
	x = gen_frame_mem (Pmode, x);
	emit_move_insn (x, gen_rtx_REG (Pmode, regno));
      }

  /* Save FPU registers.  */
  for (regno = AC0_REGNUM; regno <= AC3_REGNUM; regno++) 
    if (pdp11_saved_regno (regno))
      {
	x = gen_rtx_PRE_DEC (Pmode, stack_pointer_rtx);
	x = gen_frame_mem (DFmode, x);
	via_ac = gen_rtx_REG (DFmode, regno);
	emit_move_insn (x, via_ac);
      }

  /* ??? Maybe make ac4, ac5 call used regs?? */
  for (regno = AC4_REGNUM; regno <= AC5_REGNUM; regno++)
    if (pdp11_saved_regno (regno))
      {
	gcc_assert (via_ac != NULL);
	emit_move_insn (via_ac, gen_rtx_REG (DFmode, regno));

	x = gen_rtx_PRE_DEC (Pmode, stack_pointer_rtx);
	x = gen_frame_mem (DFmode, x);
	emit_move_insn (x, via_ac);
      }

  if (frame_pointer_needed)
    emit_move_insn (frame_pointer_rtx, stack_pointer_rtx);

  /* Make local variable space.  */
  if (fsize)
    emit_insn (gen_addhi3 (stack_pointer_rtx, stack_pointer_rtx,
			   GEN_INT (-fsize)));
}

/* Generate epilogue.  This uses the frame pointer to pop the local
   variables and any alloca data off the stack.  If there is no alloca
   and frame pointer elimination hasn't been disabled, there is no
   frame pointer and the local variables are popped by adjusting the
   stack pointer instead.  */

void
pdp11_expand_epilogue (void)
{								
  HOST_WIDE_INT fsize = get_frame_size ();
  unsigned regno;
  rtx x, reg, via_ac = NULL;

  /* Deallocate the local variables.  */
  if (fsize)
    {
      if (frame_pointer_needed)
	{
	  /* We can deallocate the frame with a single move.  */
	  emit_move_insn (stack_pointer_rtx, frame_pointer_rtx);
	}
      else
	emit_insn (gen_addhi3 (stack_pointer_rtx, stack_pointer_rtx,
			       GEN_INT (fsize)));
    }

  /* Restore the FPU registers.  */
  if (pdp11_saved_regno (AC4_REGNUM) || pdp11_saved_regno (AC5_REGNUM))
    {
      /* Find a temporary with which to restore AC4/5.  */
      for (regno = AC0_REGNUM; regno <= AC3_REGNUM; regno++)
	if (pdp11_saved_regno (regno))
	  {
	    via_ac = gen_rtx_REG (DFmode, regno);
	    break;
	  }
    }

  /* Restore registers via pops.  */

  for (regno = AC5_REGNUM; regno >= AC0_REGNUM; regno--)
    if (pdp11_saved_regno (regno))
      {
	x = gen_rtx_POST_INC (Pmode, stack_pointer_rtx);
	x = gen_frame_mem (DFmode, x);
	reg = gen_rtx_REG (DFmode, regno);

	if (LOAD_FPU_REG_P (regno))
	  emit_move_insn (reg, x);
	else
	  {
	    emit_move_insn (via_ac, x);
	    emit_move_insn (reg, via_ac);
	  }
      }

  for (regno = PC_REGNUM; regno >= R0_REGNUM + 2; regno--)
    if (pdp11_saved_regno (regno))
      {
	x = gen_rtx_POST_INC (Pmode, stack_pointer_rtx);
	x = gen_frame_mem (Pmode, x);
	emit_move_insn (gen_rtx_REG (Pmode, regno), x);
      }

  emit_jump_insn (gen_rtspc ());
}

/* Return the best assembler insn template
   for moving operands[1] into operands[0] as a fullword.  */
static const char *
singlemove_string (rtx *operands)
{
  if (operands[1] != const0_rtx)
    return "mov\t%1,%0";

  return "clr\t%0";
}


/* Expand multi-word operands (SImode or DImode) into the 2 or 4
   corresponding HImode operands.  The number of operands is given as
   the third argument, the word count for the mode as the fourth
   argument, and the required order of parts as the sixth argument.
   The word count is explicit because sometimes we're asked to compare
   two constants, both of which have mode VOIDmode, so we can't always
   rely on the input operand mode to imply the operand size.  */
bool
pdp11_expand_operands (rtx *operands, rtx exops[][2],
		       int opcount, int words,
		       pdp11_action *action, pdp11_partorder order)
{
  int op, w, i, sh;
  pdp11_partorder useorder;
  bool sameoff = false;
  enum { REGOP, OFFSOP, MEMOP, PUSHOP, POPOP, CNSTOP, RNDOP } optype;
  long sval[2];
  
  /* If either piece order is accepted and one is pre-decrement
     while the other is post-increment, set order to be high order
     word first.  That will force the pre-decrement to be turned
     into a pointer adjust, then offset addressing.
     Otherwise, if either operand uses pre-decrement, that means
     the order is low order first. 
     Otherwise, if both operands are registers and destination is
     higher than source and they overlap, do low order word (highest
     register number) first.  */
  useorder = either;
  if (opcount == 2)
    {
      if (GET_CODE (operands[0]) == MEM &&
	  GET_CODE (operands[1]) == MEM &&
	  ((GET_CODE (XEXP (operands[0], 0)) == POST_INC &&
	    GET_CODE (XEXP (operands[1], 0)) == PRE_DEC) ||
	   (GET_CODE (XEXP (operands[0], 0)) == PRE_DEC &&
	    GET_CODE (XEXP (operands[1], 0)) == POST_INC)))
	    useorder = big;
      else if ((GET_CODE (operands[0]) == MEM &&
		GET_CODE (XEXP (operands[0], 0)) == PRE_DEC) ||
	       (GET_CODE (operands[1]) == MEM &&
		GET_CODE (XEXP (operands[1], 0)) == PRE_DEC))
	useorder = little;
      else if (REG_P (operands[0]) && REG_P (operands[1]) &&
	       REGNO (operands[0]) > REGNO (operands[1]) &&
	       REGNO (operands[0]) < REGNO (operands[1]) + words)
	    useorder = little;

      /* Check for source == offset from register and dest == push of
	 the same register.  In that case, we have to use the same
	 offset (the one for the low order word) for all words, because
	 the push increases the offset to each source word.
	 In theory there are other cases like this, for example dest == pop,
	 but those don't occur in real life so ignore those.  */
      if (GET_CODE (operands[0]) ==  MEM 
	  && GET_CODE (XEXP (operands[0], 0)) == PRE_DEC
	  && REGNO (XEXP (XEXP (operands[0], 0), 0)) == STACK_POINTER_REGNUM
	  && reg_overlap_mentioned_p (stack_pointer_rtx, operands[1]))
	sameoff = true;
    }

  /* If the caller didn't specify order, use the one we computed,
     or high word first if we don't care either.  If the caller did
     specify, verify we don't have a problem with that order.
     (If it matters to the caller, constraints need to be used to
     ensure this case doesn't occur).  */
  if (order == either)
    order = (useorder == either) ? big : useorder;
  else
    gcc_assert (useorder == either || useorder == order);

  
  for (op = 0; op < opcount; op++)
    {
      /* First classify the operand.  */
      if (REG_P (operands[op]))
	optype = REGOP;
      else if (CONST_INT_P (operands[op])
	       || GET_CODE (operands[op]) == CONST_DOUBLE)
	optype = CNSTOP;
      else if (GET_CODE (XEXP (operands[op], 0)) == POST_INC)
	optype = POPOP;
      else if (GET_CODE (XEXP (operands[op], 0)) == PRE_DEC)
	optype = PUSHOP;
      else if (!reload_in_progress || offsettable_memref_p (operands[op]))
	optype = OFFSOP;
      else if (GET_CODE (operands[op]) == MEM)
	optype = MEMOP;
      else
	optype = RNDOP;

      /* Check for the cases that the operand constraints are not
	 supposed to allow to happen. Return failure for such cases.  */
      if (optype == RNDOP)
	return false;
      
      if (action != NULL)
	action[op] = no_action;
      
      /* If the operand uses pre-decrement addressing but we
	 want to get the parts high order first,
	 decrement the former register explicitly
	 and change the operand into ordinary indexing.  */
      if (optype == PUSHOP && order == big)
	{
	  gcc_assert (action != NULL);
	  action[op] = dec_before;
	  operands[op] = gen_rtx_MEM (GET_MODE (operands[op]),
				      XEXP (XEXP (operands[op], 0), 0));
	  optype = OFFSOP;
	}
      /* If the operand uses post-increment mode but we want 
	 to get the parts low order first, change the operand
	 into ordinary indexing and remember to increment
	 the register explicitly when we're done.  */
      else if (optype == POPOP && order == little)
	{
	  gcc_assert (action != NULL);
	  action[op] = inc_after;
	  operands[op] = gen_rtx_MEM (GET_MODE (operands[op]),
				      XEXP (XEXP (operands[op], 0), 0));
	  optype = OFFSOP;
	}

      if (GET_CODE (operands[op]) == CONST_DOUBLE)
	{
	  gcc_assert (GET_MODE (operands[op]) != VOIDmode);
	  REAL_VALUE_TO_TARGET_DOUBLE
	    (*CONST_DOUBLE_REAL_VALUE (operands[op]), sval);
	}
      
      for (i = 0; i < words; i++)
	{
	  if (order == big)
	    w = i;
	  else if (sameoff)
	    w = words - 1;
	  else
	    w = words - 1 - i;

	  /* Set the output operand to be word "w" of the input.  */
	  if (optype == REGOP)
	    exops[i][op] = gen_rtx_REG (HImode, REGNO (operands[op]) + w);
	  else if (optype == OFFSOP)
	    exops[i][op] = adjust_address (operands[op], HImode, w * 2);
	  else if (optype == CNSTOP)
	    {
	      if (GET_CODE (operands[op]) == CONST_DOUBLE)
		{
		  sh = 16 - (w & 1) * 16;
		  exops[i][op] = gen_rtx_CONST_INT (HImode, (sval[w / 2] >> sh) & 0xffff);
		}
	      else
		{
		  sh = ((words - 1 - w) * 16);
		  exops[i][op] = gen_rtx_CONST_INT (HImode, trunc_int_for_mode (INTVAL(operands[op]) >> sh, HImode));
		}
	    }
	  else
	    exops[i][op] = operands[op];
	}
    }
  return true;
}

/* Output assembler code to perform a multiple-word move insn
   with operands OPERANDS.  This moves 2 or 4 words depending
   on the machine mode of the operands.  */

const char *
output_move_multiple (rtx *operands)
{
  rtx inops[2];
  rtx exops[4][2];
  rtx adjops[2];
  
  pdp11_action action[2];
  int i, words;
  
  words = GET_MODE_BITSIZE (GET_MODE (operands[0])) / 16;
  adjops[1] = gen_rtx_CONST_INT (HImode, words * 2);

  inops[0] = operands[0];
  inops[1] = operands[1];
  
  pdp11_expand_operands (inops, exops, 2, words, action, either);
  
  /* Check for explicit decrement before.  */
  if (action[0] == dec_before)
    {
      adjops[0] = XEXP (XEXP (operands[0], 0), 0);
      output_asm_insn ("sub\t%1,%0", adjops);
    }
  if (action[1] == dec_before)
    {
      adjops[0] = XEXP (XEXP (operands[1], 0), 0);
      output_asm_insn ("sub\t%1,%0", adjops);
    }

  /* Do the words.  */
  for (i = 0; i < words; i++)
    output_asm_insn (singlemove_string (exops[i]), exops[i]);

  /* Check for increment after.  */
  if (action[0] == inc_after)
    {
      adjops[0] = XEXP (XEXP (operands[0], 0), 0);
      output_asm_insn ("add\t%1,%0", adjops);
    }
  if (action[1] == inc_after)
    {
      adjops[0] = XEXP (XEXP (operands[1], 0), 0);
      output_asm_insn ("add\t%1,%0", adjops);
    }

  return "";
}

/* Build an internal label.  */
void
pdp11_gen_int_label (char *label, const char *prefix, int num)
{
  if (TARGET_DEC_ASM)
    /* +1 because GCC numbers labels starting at zero.  */
    sprintf (label, "*%u$", num + 1);
  else
    sprintf (label, "*%s_%u", prefix, num);
}
  
/* Output an ascii string.  */
void
output_ascii (FILE *file, const char *p, int size)
{
  int i, c;
  const char *pseudo = "\t.ascii\t";
  bool delim = false;
  
  if (TARGET_DEC_ASM)
    {
      if (p[size - 1] == '\0')
	{
	  pseudo = "\t.asciz\t";
	  size--;
	}
      fputs (pseudo, file);
      for (i = 0; i < size; i++)
	{
	  c = *p++ & 0xff;
	  if (c < 32 || c == '"' || c > 126)
	    {
	      if (delim)
		putc ('"', file);
	      fprintf (file, "<%o>", c);
	      delim = false;
	    }
	  else
	    {
	      if (!delim)
		putc ('"', file);
	      delim = true;
	      putc (c, file);
	    }
	}
      if (delim)
	putc ('"', file);
      putc ('\n', file);
    }
  else
    {
      fprintf (file, "\t.byte ");

      for (i = 0; i < size; i++)
	{
	  fprintf (file, "%#o", *p++ & 0xff);
	  if (i < size - 1)
	    putc (',', file);
	}
      putc ('\n', file);
    }
}

void
pdp11_asm_output_var (FILE *file, const char *name, int size,
		      int align, bool global)
{
  switch_to_section (data_section);
  if (align > 8)
    fprintf (file, "\t.even\n");
  if (TARGET_DEC_ASM)
    {
      assemble_name (file, name);
      if (global)
	fputs ("::", file);
      else
	fputs (":", file);
      if (align > 8)
	fprintf (file, "\t.blkw\t%o\n", (size & 0xffff) / 2);
      else
	fprintf (file, "\t.blkb\t%o\n", size & 0xffff);
    }
  else
    {
      if (global)
	{
	  fprintf (file, ".globl ");
	  assemble_name (file, name);
	  fprintf (file, "\n");
	}
      assemble_name (file, name);
      fputs (":", file);
      ASM_OUTPUT_SKIP (file, size);
    }  
}

/* Special format operators handled here:
   # -- output the correct immediate operand marker for the assembler
        dialect.
   @ -- output the correct indirect marker for the assembler dialect.
   o -- emit a constant value as a number (not an immediate operand)
        in octal.  */
static void
pdp11_asm_print_operand (FILE *file, rtx x, int code)
{
  long sval[2];
 
  if (code == '#')
    {
      if (TARGET_DEC_ASM)
	putc ('#', file);
      else
	putc ('$', file);
    }
  else if (code == '@')
    {
      if (TARGET_UNIX_ASM)
	fprintf (file, "*");
      else
	fprintf (file, "@");
    }
  else if (GET_CODE (x) == REG)
    fprintf (file, "%s", reg_names[REGNO (x)]);
  else if (GET_CODE (x) == MEM)
    output_address (GET_MODE (x), XEXP (x, 0));
  else if (GET_CODE (x) == CONST_DOUBLE && FLOAT_MODE_P (GET_MODE (x)))
    {
      REAL_VALUE_TO_TARGET_DOUBLE (*CONST_DOUBLE_REAL_VALUE (x), sval);
      if (TARGET_DEC_ASM)
	fprintf (file, "#%lo", (sval[0] >> 16) & 0xffff);
      else
	fprintf (file, "$%#lo", (sval[0] >> 16) & 0xffff);
    }
  else
    {
      if (code != 'o')
	{
	  if (TARGET_DEC_ASM)
	    putc ('#', file);
	  else
	    putc ('$', file);
	}
      output_addr_const_pdp11 (file, x);
    }
}

static bool
pdp11_asm_print_operand_punct_valid_p (unsigned char c)
{
  return (c == '#' || c == '@');
}

void
print_operand_address (FILE *file, rtx addr)
{
  rtx breg;
  rtx offset;
  int again = 0;

 retry:

  switch (GET_CODE (addr))
    {
    case MEM:
      if (TARGET_UNIX_ASM)
	fprintf (file, "*");
      else
	fprintf (file, "@");
      addr = XEXP (addr, 0);
      again = 1;
      goto retry;

    case REG:
      fprintf (file, "(%s)", reg_names[REGNO (addr)]);
      break;

    case PRE_MODIFY:
    case PRE_DEC:
      fprintf (file, "-(%s)", reg_names[REGNO (XEXP (addr, 0))]);
      break;

    case POST_MODIFY:
    case POST_INC:
      fprintf (file, "(%s)+", reg_names[REGNO (XEXP (addr, 0))]);
      break;

    case PLUS:
      breg = 0;
      offset = 0;
      if (CONSTANT_ADDRESS_P (XEXP (addr, 0))
	  || GET_CODE (XEXP (addr, 0)) == MEM)
	{
	  offset = XEXP (addr, 0);
	  addr = XEXP (addr, 1);
	}
      else if (CONSTANT_ADDRESS_P (XEXP (addr, 1))
	       || GET_CODE (XEXP (addr, 1)) == MEM)
	{
	  offset = XEXP (addr, 1);
	  addr = XEXP (addr, 0);
	}
      if (GET_CODE (addr) != PLUS)
	;
      else if (GET_CODE (XEXP (addr, 0)) == REG)
	{
	  breg = XEXP (addr, 0);
	  addr = XEXP (addr, 1);
	}
      else if (GET_CODE (XEXP (addr, 1)) == REG)
	{
	  breg = XEXP (addr, 1);
	  addr = XEXP (addr, 0);
	}
      if (GET_CODE (addr) == REG)
	{
	  gcc_assert (breg == 0);
	  breg = addr;
	  addr = 0;
	}
      if (offset != 0)
	{
	  gcc_assert (addr == 0);
	  addr = offset;
	}
      if (addr != 0)
	output_addr_const_pdp11 (file, addr);
      if (breg != 0)
	{
	  gcc_assert (GET_CODE (breg) == REG);
	  fprintf (file, "(%s)", reg_names[REGNO (breg)]);
	}
      break;

    default:
      if (!again && GET_CODE (addr) == CONST_INT)
	{
	  /* Absolute (integer number) address.  */
	  if (TARGET_DEC_ASM)
	    fprintf (file, "@#");
	  else if (!TARGET_UNIX_ASM)
	    fprintf (file, "@$");
	}
      output_addr_const_pdp11 (file, addr);
    }
}

/* Target hook to assemble integer objects.  We need to use the
   pdp-specific version of output_addr_const.  */

static bool
pdp11_assemble_integer (rtx x, unsigned int size, int aligned_p)
{
  if (aligned_p)
    switch (size)
      {
      case 1:
	fprintf (asm_out_file, "\t.byte\t");
	output_addr_const_pdp11 (asm_out_file, GEN_INT (INTVAL (x) & 0xff));
	fputs ("\n", asm_out_file);
	return true;

      case 2:
	fprintf (asm_out_file, TARGET_UNIX_ASM ? "\t" : "\t.word\t");
	output_addr_const_pdp11 (asm_out_file, x);
	fputs ("\n", asm_out_file);
	return true;
      }
  return default_assemble_integer (x, size, aligned_p);
}


static bool
pdp11_lra_p (void)
{
  return TARGET_LRA;
}

/* Register to register moves are cheap if both are general
   registers.  */
static int 
pdp11_register_move_cost (machine_mode mode ATTRIBUTE_UNUSED,
			  reg_class_t c1, reg_class_t c2)
{
  if (CPU_REG_CLASS (c1) && CPU_REG_CLASS (c2))
    return 2;
  else if ((c1 >= LOAD_FPU_REGS && c1 <= FPU_REGS && c2 == LOAD_FPU_REGS) ||
	   (c2 >= LOAD_FPU_REGS && c2 <= FPU_REGS && c1 == LOAD_FPU_REGS))
    return 2;
  else
    return 22;
}

/* This tries to approximate what pdp11_insn_cost would do, but
   without visibility into the actual instruction being generated it's
   inevitably a rough approximation.  */
static bool
pdp11_rtx_costs (rtx x, machine_mode mode, int outer_code,
		 int opno ATTRIBUTE_UNUSED, int *total, bool speed)
{
  const int code = GET_CODE (x);
  const int asize = (mode == QImode) ? 2 : GET_MODE_SIZE (mode);
  rtx src, dest;
  const char *fmt;
  
  switch (code)
    {
    case CONST_INT:
      /* Treat -1, 0, 1 as things that are optimized as clr or dec
	 etc. though that doesn't apply to every case.  */
      if (INTVAL (x) >= -1 && INTVAL (x) <= 1)
	{
	  *total = 0;
	  return true;
	}
      /* FALL THROUGH.  */
    case REG:
    case MEM:
    case CONST:
    case LABEL_REF:
    case SYMBOL_REF:
    case CONST_DOUBLE:
      *total = pdp11_addr_cost (x, mode, ADDR_SPACE_GENERIC, speed);
      return true;
    }
  if (GET_RTX_LENGTH (code) == 0)
    {
      if (speed)
	*total = 0;
      else
	*total = 2;
      return true;
    }

  /* Pick up source and dest.  We don't necessarily use the standard
     recursion in rtx_costs to figure the cost, because that would
     count the destination operand twice for three-operand insns.
     Also, this way we can catch special cases like move of zero, or
     add one.  */
  fmt = GET_RTX_FORMAT (code);
  if (fmt[0] != 'e' || (GET_RTX_LENGTH (code) > 1 && fmt[1] != 'e'))
    {
      if (speed)
	*total = 0;
      else
	*total = 2;
      return true;
    }
  if (GET_RTX_LENGTH (code) > 1)
    src = XEXP (x, 1);
  dest = XEXP (x, 0);
      
  /* If optimizing for size, claim everything costs 2 per word, plus
     whatever the operands require.  */
  if (!speed)
    *total = asize;
  else
    {
      if (FLOAT_MODE_P (mode))
	{
	  switch (code)
	    {
	    case MULT:
	    case DIV:
	    case MOD:
	      *total = 20;
	      break;

	    case COMPARE:
	      *total = 4;
	      break;

	    case PLUS:
	    case MINUS:
	      *total = 6;
	      break;

	    default:
	      *total = 2;
	      break;
	    }
	}
      else
	{
	  /* Integer operations are scaled for SI and DI modes, though the
	     scaling is not exactly accurate.  */
	  switch (code)
	    {
	    case MULT:
	      *total = 5 * asize * asize;
	      break;

	    case DIV:
	      *total = 10 * asize * asize;
	      break;
	  
	    case MOD:
	      /* Fake value because it's accounted for under DIV, since we
		 use a divmod pattern.  */
	      total = 0;
	      break;

	    case ASHIFT:
	    case ASHIFTRT:
	    case LSHIFTRT:
	      /* This is a bit problematic because the cost depends on the
		 shift amount.  Make it <asize> for now, which is for the
		 case of a one bit shift.  */
	      *total = asize;
	      break;
	  
	    default:
	      *total = asize;
	      break;
	    }
	}
    }
  
  /* Now see if we're looking at a SET.  If yes, then look at the
     source to see if this is a move or an arithmetic operation, and
     continue accordingly to handle the operands.  */
  if (code == SET)
    {
      switch (GET_CODE (src))
	{
	case REG:
	case MEM:
	case CONST_INT:
	case CONST:
	case LABEL_REF:
	case SYMBOL_REF:
	case CONST_DOUBLE:
	  /* It's a move.  */
	  *total += pdp11_addr_cost (dest, mode, ADDR_SPACE_GENERIC, speed);
	  if (src != const0_rtx)
	    *total += pdp11_addr_cost (src, mode, ADDR_SPACE_GENERIC, speed);
	  return true;
	default:
	  /* Not a move.  Get the cost of the source operand and add
	     that in, but not the destination operand since we're
	     dealing with read/modify/write operands.  */
	  *total += rtx_cost (src, mode, (enum rtx_code) outer_code, 1, speed);
	  return true;
	}
    }
  else if (code == PLUS || code == MINUS)
    {
      if (GET_CODE (src) == CONST_INT &&
	  (INTVAL (src) == 1 || INTVAL (src) == -1))
	{
	  *total += rtx_cost (dest, mode, (enum rtx_code) outer_code, 0, speed);
	  return true;
	}
    }
  return false;
}

/* Return cost of accessing the supplied operand.  Registers are free.
   Anything else starts with a cost of two.  Add to that for memory
   references the memory accesses of the addressing mode (if any) plus
   the data reference; for other operands just the memory access (if
   any) for the mode.  */
static int
pdp11_addr_cost (rtx addr, machine_mode mode, addr_space_t as ATTRIBUTE_UNUSED,
		 bool speed)
{
  int cost = 0;
  
  if (GET_CODE (addr) != REG)
    {
      if (!simple_memory_operand (addr, mode))
	cost = 2;

      /* If optimizing for speed, account for the memory reference if
	 any.  */
      if (speed && !CONSTANT_P (addr))
	cost += (mode == QImode) ? 2 : GET_MODE_SIZE (mode);
    }
  return cost;
}


static int
pdp11_insn_cost (rtx_insn *insn, bool speed)
{
  int base_cost;
  rtx pat, set, dest, src, src2;
  machine_mode mode;
  enum rtx_code op;

  if (recog_memoized (insn) < 0)
    return 0;

  /* If optimizing for size, we want the insn size.  */
  if (!speed)
    return get_attr_length (insn);
  else
    {
      /* Optimizing for speed.  Get the base cost of the insn, then
	 adjust for the cost of accessing operands.  Zero means use
	 the length as the cost even when optimizing for speed.  */
      base_cost = get_attr_base_cost (insn);
      if (base_cost <= 0)
	base_cost = get_attr_length (insn);
    }
  /* Look for the operands.  Often we have a PARALLEL that's either
     the actual operation plus a clobber, or the implicit compare plus
     the actual operation.  Find the actual operation.  */
  pat = PATTERN (insn);
  
  if (GET_CODE (pat) == PARALLEL)
    {
      set = XVECEXP (pat, 0, 0);
      if (GET_CODE (set) != SET || GET_CODE (XEXP (set, 1)) == COMPARE)
	set = XVECEXP (pat, 0, 1);
      if (GET_CODE (set) != SET || GET_CODE (XEXP (set, 1)) == COMPARE)
	return 0;
    }
  else
    {
      set = pat;
      if (GET_CODE (set) != SET)
	return 0;
    }
  
  /* Pick up the SET source and destination RTL.  */
  dest = XEXP (set, 0);
  src = XEXP (set, 1);
  mode = GET_MODE (dest);

  /* See if we have a move, or some arithmetic operation.  If a move,
     account for source and destination operand costs.  Otherwise,
     account for the destination and for the second operand of the
     operation -- the first is also destination and we don't want to
     double-count it.  */
  base_cost += pdp11_addr_cost (dest, mode, ADDR_SPACE_GENERIC, speed);
  op = GET_CODE (src);
  switch (op)
    {
    case REG:
    case MEM:
    case CONST_INT:
    case CONST:
    case LABEL_REF:
    case SYMBOL_REF:
    case CONST_DOUBLE:
      /* It's a move.  */
      if (src != const0_rtx)
	base_cost += pdp11_addr_cost (src, mode, ADDR_SPACE_GENERIC, speed);
      return base_cost;
    default:
      break;
    }
  /* There are some other cases where souce and dest are distinct.  */
  if (FLOAT_MODE_P (mode) &&
      (op == FLOAT_TRUNCATE || op == FLOAT_EXTEND || op == FIX || op == FLOAT))
    {
      src2 = XEXP (src, 0);
      base_cost += pdp11_addr_cost (src2, mode, ADDR_SPACE_GENERIC, speed);
    }
  /* Otherwise, pick up the second operand of the arithmetic
     operation, if it has two operands.  */
  else if (op != SUBREG && op != UNSPEC && GET_RTX_LENGTH (op) > 1)
    {
      src2 = XEXP (src, 1);
      base_cost += pdp11_addr_cost (src2, mode, ADDR_SPACE_GENERIC, speed);
    }
  
  return base_cost;
}

const char *
output_jump (rtx *operands, int ccnz, int length)
{
  rtx tmpop[1];
  static char buf[100];
  const char *pos, *neg;
  enum rtx_code code = GET_CODE (operands[0]);

  if (ccnz)
    {
      /* These are the branches valid for CCNZmode, i.e., a comparison
	 with zero where the V bit is not set to zero.  These cases
	 occur when CC or FCC are set as a side effect of some data
	 manipulation, such as the ADD instruction.  */
      switch (code)
	{
	case EQ: pos = "beq", neg = "bne"; break;
	case NE: pos = "bne", neg = "beq"; break;
	case LT: pos = "bmi", neg = "bpl"; break;
	case GE: pos = "bpl", neg = "bmi"; break;
	default: gcc_unreachable ();
	}
    }
  else
    {
      switch (code)
	{
	case EQ: pos = "beq", neg = "bne"; break;
	case NE: pos = "bne", neg = "beq"; break;
	case GT: pos = "bgt", neg = "ble"; break;
	case GTU: pos = "bhi", neg = "blos"; break;
	case LT: pos = "blt", neg = "bge"; break;
	case LTU: pos = "blo", neg = "bhis"; break;
	case GE: pos = "bge", neg = "blt"; break;
	case GEU: pos = "bhis", neg = "blo"; break;
	case LE: pos = "ble", neg = "bgt"; break;
	case LEU: pos = "blos", neg = "bhi"; break;
	default: gcc_unreachable ();
	}
    }
  switch (length)
    {
    case 2:
      sprintf (buf, "%s\t%%l1", pos);
      return buf;
    case 6:
      tmpop[0] = gen_label_rtx ();
      sprintf (buf, "%s\t%%l0", neg);
      output_asm_insn (buf, tmpop);
      output_asm_insn ("jmp\t%l1", operands);
      output_asm_label (tmpop[0]);
      fputs (":\n", asm_out_file);
      return "";
    default:
      gcc_unreachable ();
    }
}

/* Select the CC mode to be used for the side effect compare with
   zero, given the compare operation code in op and the compare
   operands in x in and y.  */
machine_mode
pdp11_cc_mode (enum rtx_code op ATTRIBUTE_UNUSED, rtx x, rtx y ATTRIBUTE_UNUSED)
{
  if (FLOAT_MODE_P (GET_MODE (x)))
    {
      switch (GET_CODE (x))
	{
	case ABS:
	case NEG:
	case REG:
	case MEM:
	  return CCmode;
	default:
	  return CCNZmode;
	}
    }
  else
    {
      switch (GET_CODE (x))
	{
	case XOR:
	case AND:
	case IOR:
	case MULT:
	case NOT:
	case REG:
	case MEM:
	  return CCmode;
	default:
	  return CCNZmode;
	}
    }
}


int
simple_memory_operand(rtx op, machine_mode mode ATTRIBUTE_UNUSED)
{
  rtx addr;

  /* Eliminate non-memory operations */
  if (GET_CODE (op) != MEM)
    return FALSE;

  /* Decode the address now.  */

 indirection:
    
  addr = XEXP (op, 0);

  switch (GET_CODE (addr))
    {
    case REG:
      /* (R0) - no extra cost */
      return 1;
	
    case PRE_DEC:
    case POST_INC:
    case PRE_MODIFY:
    case POST_MODIFY:
      /* -(R0), (R0)+ - cheap! */
      return 1;
	
    case MEM:
      /* cheap - is encoded in addressing mode info! 

	 -- except for @(R0), which has to be @0(R0) !!! */

      if (GET_CODE (XEXP (addr, 0)) == REG)
	return 0;
	
      op=addr;
      goto indirection;
	
    case CONST_INT:
    case LABEL_REF:	       
    case CONST:
    case SYMBOL_REF:
      /* @#address - extra cost */
      return 0;

    case PLUS:
      /* X(R0) - extra cost */
      return 0;

    default:
      break;
    }
    
  return FALSE;
}

/* Similar to simple_memory_operand but doesn't match push/pop.  */
int
no_side_effect_operand(rtx op, machine_mode mode ATTRIBUTE_UNUSED)
{
  rtx addr;

  /* Eliminate non-memory operations */
  if (GET_CODE (op) != MEM)
    return FALSE;

  /* Decode the address now.  */

 indirection:
    
  addr = XEXP (op, 0);

  switch (GET_CODE (addr))
    {
    case REG:
      /* (R0) - no extra cost */
      return 1;
	
    case PRE_DEC:
    case POST_INC:
    case PRE_MODIFY:
    case POST_MODIFY:
      return 0;
	
    case MEM:
      /* cheap - is encoded in addressing mode info! 

	 -- except for @(R0), which has to be @0(R0) !!! */

      if (GET_CODE (XEXP (addr, 0)) == REG)
	return 0;
	
      op=addr;
      goto indirection;
	
    case CONST_INT:
    case LABEL_REF:	       
    case CONST:
    case SYMBOL_REF:
      /* @#address - extra cost */
      return 0;

    case PLUS:
      /* X(R0) - extra cost */
      return 0;

    default:
      break;
    }
    
  return FALSE;
}

/* Return TRUE if op is a push or pop using the register "regno".  */
bool
pushpop_regeq (rtx op, int regno)
{
  rtx addr;

  /* False if not memory reference.  */
  if (GET_CODE (op) != MEM)
    return FALSE;

  /* Get the address of the memory reference.  */
  addr = XEXP (op, 0);

  if (GET_CODE (addr) == MEM)
    addr = XEXP (addr, 0);

  switch (GET_CODE (addr))
    {
    case PRE_DEC:
    case POST_INC:
    case PRE_MODIFY:
    case POST_MODIFY:
      return REGNO (XEXP (addr, 0)) == (unsigned) regno;
    default:
      return FALSE;
    }
}

/* This function checks whether a real value can be encoded as
   a literal, i.e., addressing mode 27.  In that mode, real values
   are one word values, so the remaining 48 bits have to be zero.  */
int
legitimate_const_double_p (rtx address)
{
  long sval[2];

  /* If it's too big for HOST_WIDE_INT, it's definitely to big here.  */
  if (GET_MODE (address) == VOIDmode)
    return 0;
  REAL_VALUE_TO_TARGET_DOUBLE (*CONST_DOUBLE_REAL_VALUE (address), sval);

  if ((sval[0] & 0xffff) == 0 && sval[1] == 0)
    return 1;
  return 0;
}

/* Implement TARGET_CAN_CHANGE_MODE_CLASS.  */
static bool
pdp11_can_change_mode_class (machine_mode from,
			     machine_mode to,
			     reg_class_t rclass)
{
  /* Also, FPU registers contain a whole float value and the parts of
     it are not separately accessible.

     So we disallow all mode changes involving FPRs.  */
  if (FLOAT_MODE_P (from) != FLOAT_MODE_P (to))
    return false;
  
  return !reg_classes_intersect_p (FPU_REGS, rclass);
}

/* Implement TARGET_CXX_GUARD_TYPE */
static tree
pdp11_guard_type (void)
{
  return short_integer_type_node;
}

/* TARGET_PREFERRED_RELOAD_CLASS

   Given an rtx X being reloaded into a reg required to be
   in class CLASS, return the class of reg to actually use.
   In general this is just CLASS; but on some machines
   in some cases it is preferable to use a more restrictive class.  

loading is easier into LOAD_FPU_REGS than FPU_REGS! */

static reg_class_t
pdp11_preferred_reload_class (rtx x, reg_class_t rclass)
{
  if (rclass == FPU_REGS)
    return LOAD_FPU_REGS;
  if (rclass == ALL_REGS)
    {
      if (FLOAT_MODE_P (GET_MODE (x)))
	return LOAD_FPU_REGS;
      else
	return GENERAL_REGS;
    }
  return rclass;
}

/* TARGET_PREFERRED_OUTPUT_RELOAD_CLASS

   Given an rtx X being reloaded into a reg required to be
   in class CLASS, return the class of reg to actually use.
   In general this is just CLASS; but on some machines
   in some cases it is preferable to use a more restrictive class.  

loading is easier into LOAD_FPU_REGS than FPU_REGS! */

static reg_class_t
pdp11_preferred_output_reload_class (rtx x, reg_class_t rclass)
{
  if (rclass == FPU_REGS)
    return LOAD_FPU_REGS;
  if (rclass == ALL_REGS)
    {
      if (FLOAT_MODE_P (GET_MODE (x)))
	return LOAD_FPU_REGS;
      else
	return GENERAL_REGS;
    }
  return rclass;
}


/* TARGET_SECONDARY_RELOAD.

   FPU registers AC4 and AC5 (class NO_LOAD_FPU_REGS) require an 
   intermediate register (AC0-AC3: LOAD_FPU_REGS).  Everything else
   can be loaded/stored directly.  */
static reg_class_t 
pdp11_secondary_reload (bool in_p ATTRIBUTE_UNUSED,
			rtx x,
			reg_class_t reload_class,
			machine_mode reload_mode ATTRIBUTE_UNUSED,
			secondary_reload_info *sri ATTRIBUTE_UNUSED)
{
  if (reload_class != NO_LOAD_FPU_REGS || GET_CODE (x) != REG ||
      REGNO_REG_CLASS (REGNO (x)) == LOAD_FPU_REGS)
    return NO_REGS;
  
  return LOAD_FPU_REGS;
}

/* Implement TARGET_SECONDARY_MEMORY_NEEDED.

   The answer is yes if we're going between general register and FPU
   registers.  The mode doesn't matter in making this check.  */
static bool
pdp11_secondary_memory_needed (machine_mode, reg_class_t c1, reg_class_t c2)
{
  int fromfloat = (c1 == LOAD_FPU_REGS || c1 == NO_LOAD_FPU_REGS || 
		   c1 == FPU_REGS);
  int tofloat = (c2 == LOAD_FPU_REGS || c2 == NO_LOAD_FPU_REGS || 
		 c2 == FPU_REGS);
  
  return (fromfloat != tofloat);
}

/* TARGET_LEGITIMATE_ADDRESS_P recognizes an RTL expression
   that is a valid memory address for an instruction.
   The MODE argument is the machine mode for the MEM expression
   that wants to use this address.

*/

static bool
pdp11_legitimate_address_p (machine_mode mode,
			    rtx operand, bool strict)
{
    rtx xfoob;

    /* accept @#address */
    if (CONSTANT_ADDRESS_P (operand))
      return true;
    
    switch (GET_CODE (operand))
      {
      case REG:
	/* accept (R0) */
	return !strict || REGNO_OK_FOR_BASE_P (REGNO (operand));
    
      case PLUS:
	/* accept X(R0) */
	return GET_CODE (XEXP (operand, 0)) == REG
	  && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (operand, 0))))
	  && CONSTANT_ADDRESS_P (XEXP (operand, 1));

      case PRE_DEC:
	/* accept -(R0) */
	return GET_CODE (XEXP (operand, 0)) == REG
	  && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (operand, 0))));

      case POST_INC:
	/* accept (R0)+ */
	return GET_CODE (XEXP (operand, 0)) == REG
	  && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (operand, 0))));

      case PRE_MODIFY:
	/* accept -(SP) -- which uses PRE_MODIFY for byte mode */
	return GET_CODE (XEXP (operand, 0)) == REG
	  && REGNO (XEXP (operand, 0)) == STACK_POINTER_REGNUM
	  && GET_CODE ((xfoob = XEXP (operand, 1))) == PLUS
	  && GET_CODE (XEXP (xfoob, 0)) == REG
	  && REGNO (XEXP (xfoob, 0)) == STACK_POINTER_REGNUM
	  && CONST_INT_P (XEXP (xfoob, 1))
	  && INTVAL (XEXP (xfoob,1)) == -2;

      case POST_MODIFY:
	/* accept (SP)+ -- which uses POST_MODIFY for byte mode */
	return GET_CODE (XEXP (operand, 0)) == REG
	  && REGNO (XEXP (operand, 0)) == STACK_POINTER_REGNUM
	  && GET_CODE ((xfoob = XEXP (operand, 1))) == PLUS
	  && GET_CODE (XEXP (xfoob, 0)) == REG
	  && REGNO (XEXP (xfoob, 0)) == STACK_POINTER_REGNUM
	  && CONST_INT_P (XEXP (xfoob, 1))
	  && INTVAL (XEXP (xfoob,1)) == 2;

      case MEM:
	/* handle another level of indirection ! */
	xfoob = XEXP (operand, 0);

	/* (MEM:xx (MEM:xx ())) is not valid for SI, DI and currently
	   also forbidden for float, because we have to handle this 
	   in output_move_double and/or output_move_quad() - we could
	   do it, but currently it's not worth it!!! 
	   now that DFmode cannot go into CPU register file, 
	   maybe I should allow float ... 
	   but then I have to handle memory-to-memory moves in movdf ??  */
	if (GET_MODE_BITSIZE(mode) > 16)
	  return false;

	/* accept @address */
	if (CONSTANT_ADDRESS_P (xfoob))
	  return true;

	switch (GET_CODE (xfoob))
	  {
	  case REG:
	    /* accept @(R0) - which is @0(R0) */
	    return !strict || REGNO_OK_FOR_BASE_P(REGNO (xfoob));

	  case PLUS:
	    /* accept @X(R0) */
	    return GET_CODE (XEXP (xfoob, 0)) == REG
	      && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (xfoob, 0))))
	      && CONSTANT_ADDRESS_P (XEXP (xfoob, 1));

	  case PRE_DEC:
	    /* accept @-(R0) */
	    return GET_CODE (XEXP (xfoob, 0)) == REG
	      && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (xfoob, 0))));

	  case POST_INC:
	    /* accept @(R0)+ */
	    return GET_CODE (XEXP (xfoob, 0)) == REG
	      && (!strict || REGNO_OK_FOR_BASE_P (REGNO (XEXP (xfoob, 0))));

	  default:
	    /* anything else is invalid */
	    return false;
	  }

      default:
	/* anything else is invalid */
	return false;
      }
}

/* Return the class number of the smallest class containing
   reg number REGNO.  */
enum reg_class
pdp11_regno_reg_class (int regno)
{ 
  if (regno == ARG_POINTER_REGNUM)
    return NOTSP_REG;
  else if (regno == CC_REGNUM || regno == FCC_REGNUM)
    return CC_REGS;
  else if (regno > AC3_REGNUM)
    return NO_LOAD_FPU_REGS;
  else if (regno >= AC0_REGNUM)
    return LOAD_FPU_REGS;
  else if (regno == 6)
    return NOTR0_REG;
  else if (regno < 6)
    return NOTSP_REG;
  else
    return GENERAL_REGS;
}

/* Return the regnums of the CC registers.  */
bool
pdp11_fixed_cc_regs (unsigned int *p1, unsigned int *p2)
{
  *p1 = CC_REGNUM;
  *p2 = FCC_REGNUM;
  return true;
}

static int
pdp11_reg_save_size (void)
{
  int offset = 0, regno;

  for (regno = 0; regno <= PC_REGNUM; regno++)
    if (pdp11_saved_regno (regno))
      offset += 2;
  for (regno = AC0_REGNUM; regno <= AC5_REGNUM; regno++)
    if (pdp11_saved_regno (regno))
      offset += 8;
  
  return offset;
}   

/* Return the offset between two registers, one to be eliminated, and the other
   its replacement, at the start of a routine.  */

int
pdp11_initial_elimination_offset (int from, int to)
{
  /* Get the size of the register save area.  */

  if (from == FRAME_POINTER_REGNUM && to == STACK_POINTER_REGNUM)
    return get_frame_size ();
  else if (from == ARG_POINTER_REGNUM && to == FRAME_POINTER_REGNUM)
    return pdp11_reg_save_size () + 2;
  else if (from == ARG_POINTER_REGNUM && to == STACK_POINTER_REGNUM)
    return pdp11_reg_save_size () + 2 + get_frame_size ();
  else
    gcc_assert (0);
}

/* A copy of output_addr_const modified for pdp11 expression syntax.
   output_addr_const also gets called for %cDIGIT and %nDIGIT, which we don't
   use, and for debugging output, which we don't support with this port either.
   So this copy should get called whenever needed.
*/
void
output_addr_const_pdp11 (FILE *file, rtx x)
{
  char buf[256];
  int i;
  
 restart:
  switch (GET_CODE (x))
    {
    case PC:
      gcc_assert (flag_pic);
      putc ('.', file);
      break;

    case SYMBOL_REF:
      assemble_name (file, XSTR (x, 0));
      break;

    case LABEL_REF:
      ASM_GENERATE_INTERNAL_LABEL (buf, "L", CODE_LABEL_NUMBER (XEXP (x, 0)));
      assemble_name (file, buf);
      break;

    case CODE_LABEL:
      ASM_GENERATE_INTERNAL_LABEL (buf, "L", CODE_LABEL_NUMBER (x));
      assemble_name (file, buf);
      break;

    case CONST_INT:
      i = INTVAL (x);
      if (i < 0)
	{
	  i = -i;
	  fprintf (file, "-");
	}
      if (TARGET_DEC_ASM)
	fprintf (file, "%o", i & 0xffff);
      else
	fprintf (file, "%#o", i & 0xffff);
      break;

    case CONST:
      output_addr_const_pdp11 (file, XEXP (x, 0));
      break;

    case PLUS:
      /* Some assemblers need integer constants to appear last (e.g. masm).  */
      if (GET_CODE (XEXP (x, 0)) == CONST_INT)
	{
	  output_addr_const_pdp11 (file, XEXP (x, 1));
	  if (INTVAL (XEXP (x, 0)) >= 0)
	    fprintf (file, "+");
	  output_addr_const_pdp11 (file, XEXP (x, 0));
	}
      else
	{
	  output_addr_const_pdp11 (file, XEXP (x, 0));
	  if (INTVAL (XEXP (x, 1)) >= 0)
	    fprintf (file, "+");
	  output_addr_const_pdp11 (file, XEXP (x, 1));
	}
      break;

    case MINUS:
      /* Avoid outputting things like x-x or x+5-x,
	 since some assemblers can't handle that.  */
      x = simplify_subtraction (x);
      if (GET_CODE (x) != MINUS)
	goto restart;

      output_addr_const_pdp11 (file, XEXP (x, 0));
      if (GET_CODE (XEXP (x, 1)) != CONST_INT
	  || INTVAL (XEXP (x, 1)) >= 0)
	fprintf (file, "-");
      output_addr_const_pdp11 (file, XEXP (x, 1));
      break;

    case ZERO_EXTEND:
    case SIGN_EXTEND:
      output_addr_const_pdp11 (file, XEXP (x, 0));
      break;

    default:
      output_operand_lossage ("invalid expression as operand");
    }
}

/* Worker function for TARGET_RETURN_IN_MEMORY.  */

static bool
pdp11_return_in_memory (const_tree type, const_tree fntype ATTRIBUTE_UNUSED)
{
  /* Integers 32 bits and under, and scalar floats (if FPU), are returned
     in registers.  The rest go into memory.  */
  return (TYPE_MODE (type) == DImode
	  || (FLOAT_MODE_P (TYPE_MODE (type)) && ! TARGET_AC0)
	  || VECTOR_TYPE_P (type)
	  || COMPLEX_MODE_P (TYPE_MODE (type)));
}

/* Worker function for TARGET_FUNCTION_VALUE.

   On the pdp11 the value is found in R0 (or ac0??? not without FPU!!!! )  */

static rtx
pdp11_function_value (const_tree valtype, 
 		      const_tree fntype_or_decl ATTRIBUTE_UNUSED,
 		      bool outgoing ATTRIBUTE_UNUSED)
{
  return gen_rtx_REG (TYPE_MODE (valtype),
		      BASE_RETURN_VALUE_REG(TYPE_MODE(valtype)));
}

/* Worker function for TARGET_LIBCALL_VALUE.  */

static rtx
pdp11_libcall_value (machine_mode mode,
                     const_rtx fun ATTRIBUTE_UNUSED)
{
  return  gen_rtx_REG (mode, BASE_RETURN_VALUE_REG(mode));
}

/* Worker function for TARGET_FUNCTION_VALUE_REGNO_P.

   On the pdp, the first "output" reg is the only register thus used.

   maybe ac0 ? - as option someday!  */

static bool
pdp11_function_value_regno_p (const unsigned int regno)
{
  return (regno == RETVAL_REGNUM) || (TARGET_AC0 && (regno == AC0_REGNUM));
}

/* Used for O constraint, matches if shift count is "small".  */
bool
pdp11_small_shift (int n)
{
  return (unsigned) n < 4;
}

/* Expand a shift insn.  Returns true if the expansion was done,
   false if it needs to be handled by the caller.  */
bool
pdp11_expand_shift (rtx *operands, rtx (*shift_sc) (rtx, rtx, rtx),
		    rtx (*shift_base) (rtx, rtx, rtx))
{
  rtx r, test;
  rtx_code_label *lb;
  
  if (CONST_INT_P (operands[2]) && pdp11_small_shift (INTVAL (operands[2])))
    emit_insn ((*shift_sc) (operands[0], operands[1], operands[2]));
  else if (TARGET_40_PLUS)
    return false;
  else
    {
      lb = gen_label_rtx ();
      r = gen_reg_rtx (HImode);
      emit_move_insn (operands[0], operands[1]);
      emit_move_insn (r, operands[2]);
      if (!CONST_INT_P (operands[2]))
	{
	  test = gen_rtx_LE (HImode, r, const0_rtx);
	  emit_jump_insn (gen_cbranchhi4 (test, r, const0_rtx, lb));
	}
      /* It would be nice to expand the loop here, but that's not
	 possible because shifts may be generated by the loop unroll
	 optimizer and it doesn't appreciate flow changes happening
	 while it's doing things.  */
      emit_insn ((*shift_base) (operands[0], operands[1], r));
      if (!CONST_INT_P (operands[2]))
	{
	  emit_label (lb);

	  /* Allow REG_NOTES to be set on last insn (labels don't have enough
	     fields, and can't be used for REG_NOTES anyway).  */
	  emit_use (stack_pointer_rtx);
	}
    }
  return true;
}

/* Emit the instructions needed to produce a shift by a small constant
   amount (unrolled), or a shift made from a loop for the base machine
   case.  */
const char *
pdp11_assemble_shift (rtx *operands, machine_mode m, int code)
{
  int i, n;
  rtx inops[2];
  rtx exops[2][2];
  rtx lb[1];
  pdp11_action action[2];
  const bool small = CONST_INT_P (operands[2]) && pdp11_small_shift (INTVAL (operands[2]));

  gcc_assert (small || !TARGET_40_PLUS);

  if (m == E_SImode)
    {
      inops[0] = operands[0];
      pdp11_expand_operands (inops, exops, 1, 2, action, either);
    }
  
  if (!small)
    {
      /* Loop case, generate the top of loop label.  */
      lb[0] = gen_label_rtx ();
      output_asm_label (lb[0]);
      fputs (":\n", asm_out_file);
      n = 1;
    }
  else
    n = INTVAL (operands[2]);
  if (code == LSHIFTRT)
    {
      output_asm_insn ("clc", NULL);
      switch (m)
	{
	case E_QImode:
	  output_asm_insn ("rorb\t%0", operands);
	  break;
	case E_HImode:
	  output_asm_insn ("ror\t%0", operands);
	  break;
	case E_SImode:
	  output_asm_insn ("ror\t%0", exops[0]);
	  output_asm_insn ("ror\t%0", exops[1]);
	  break;
	default:
	  gcc_unreachable ();
	}
      n--;
    }
  for (i = 0; i < n; i++)
    {
      switch (code)
	{
	case LSHIFTRT:
	case ASHIFTRT:
	  switch (m)
	    {
	    case E_QImode:
	      output_asm_insn ("asrb\t%0", operands);
	      break;
	    case E_HImode:
	      output_asm_insn ("asr\t%0", operands);
	      break;
	    case E_SImode:
	      output_asm_insn ("asr\t%0", exops[0]);
	      output_asm_insn ("ror\t%0", exops[1]);
	      break;
	    default:
	      gcc_unreachable ();
	    }
	  break;
	case ASHIFT:
	  switch (m)
	    {
	    case E_QImode:
	      output_asm_insn ("aslb\t%0", operands);
	      break;
	    case E_HImode:
	      output_asm_insn ("asl\t%0", operands);
	      break;
	    case E_SImode:
	      output_asm_insn ("asl\t%0", exops[1]);
	      output_asm_insn ("rol\t%0", exops[0]);
	      break;
	    default:
	      gcc_unreachable ();
	    }
	  break;
	}
    }
  if (!small)
    {
      /* Loop case, emit the count-down and branch if not done.  */
      output_asm_insn ("dec\t%2", operands);
      output_asm_insn ("bne\t%l0", lb);
    }
  return "";
}

/* Figure out the length of the instructions that will be produced for
   the given operands by pdp11_assemble_shift above.  */
int
pdp11_shift_length (rtx *operands, machine_mode m, int code, bool simple_operand_p)
{
  int shift_size;

  /* Shift by 1 is 2 bytes if simple operand, 4 bytes if 2-word addressing mode.  */
  shift_size = simple_operand_p ? 2 : 4;

  /* In SImode, two shifts are needed per data item.  */
  if (m == E_SImode)
    shift_size *= 2;

  /* If shifting by a small constant, the loop is unrolled by the
     shift count.  Otherwise, account for the size of the decrement
     and branch.  */
  if (CONST_INT_P (operands[2]) && pdp11_small_shift (INTVAL (operands[2])))
    shift_size *= INTVAL (operands[2]);
  else
    shift_size += 4;

  /* Logical right shift takes one more instruction (CLC).  */
  if (code == LSHIFTRT)
    shift_size += 2;

  return shift_size;
}

/* Return the length of 2 or 4 word integer compares.  */
int
pdp11_cmp_length (rtx *operands, int words)
{
  rtx inops[2];
  rtx exops[4][2];
  int i, len = 0;

  if (!reload_completed)
    return 2;

  inops[0] = operands[0];
  inops[1] = operands[1];

  pdp11_expand_operands (inops, exops, 2, words, NULL, big);

  for (i = 0; i < words; i++)
    {
      len += 4;    /* cmp instruction word and branch that follows.  */
      if (!REG_P (exops[i][0]) &&
	  !simple_memory_operand (exops[i][0], HImode))
	len += 2;  /* first operand extra word.  */
      if (!REG_P (exops[i][1]) &&
	  !simple_memory_operand (exops[i][1], HImode) &&
	  !(CONST_INT_P (exops[i][1]) && INTVAL (exops[i][1]) == 0))
	len += 2;  /* second operand extra word.  */
    }

  /* Deduct one word because there is no branch at the end.  */
  return len - 2;
}

/* Prepend to CLOBBERS hard registers that are automatically clobbered
   for an asm We do this for CC_REGNUM and FCC_REGNUM (on FPU target)
   to maintain source compatibility with the original cc0-based
   compiler.  */

static rtx_insn *
pdp11_md_asm_adjust (vec<rtx> & /*outputs*/, vec<rtx> & /*inputs*/,
		     vec<machine_mode> & /*input_modes*/,
		     vec<const char *> & /*constraints*/, vec<rtx> &clobbers,
		     HARD_REG_SET &clobbered_regs, location_t /*loc*/)
{
  clobbers.safe_push (gen_rtx_REG (CCmode, CC_REGNUM));
  SET_HARD_REG_BIT (clobbered_regs, CC_REGNUM);
  if (TARGET_FPU)
    {
      clobbers.safe_push (gen_rtx_REG (CCmode, FCC_REGNUM));
      SET_HARD_REG_BIT (clobbered_regs, FCC_REGNUM);
    }
  return NULL;
}

/* Worker function for TARGET_TRAMPOLINE_INIT.

   trampoline - how should i do it in separate i+d ? 
   have some allocate_trampoline magic??? 

   the following should work for shared I/D:

   MOV	#STATIC, $4	01270Y	0x0000 <- STATIC; Y = STATIC_CHAIN_REGNUM
   JMP	@#FUNCTION	000137  0x0000 <- FUNCTION
*/
static void
pdp11_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
{
  rtx fnaddr = XEXP (DECL_RTL (fndecl), 0);
  rtx mem;

  gcc_assert (!TARGET_SPLIT);

  mem = adjust_address (m_tramp, HImode, 0);
  emit_move_insn (mem, GEN_INT (012700+STATIC_CHAIN_REGNUM));
  mem = adjust_address (m_tramp, HImode, 2);
  emit_move_insn (mem, chain_value);
  mem = adjust_address (m_tramp, HImode, 4);
  emit_move_insn (mem, GEN_INT (000137));
  emit_move_insn (mem, fnaddr);
}

/* Worker function for TARGET_FUNCTION_ARG.  */

static rtx
pdp11_function_arg (cumulative_args_t, const function_arg_info &)
{
  return NULL_RTX;
}

/* Worker function for TARGET_FUNCTION_ARG_ADVANCE.

   Update the data in CUM to advance over argument ARG.  */

static void
pdp11_function_arg_advance (cumulative_args_t cum_v,
			    const function_arg_info &arg)
{
  CUMULATIVE_ARGS *cum = get_cumulative_args (cum_v);

  *cum += arg.promoted_size_in_bytes ();
}

/* Make sure everything's fine if we *don't* have an FPU.
   This assumes that putting a register in fixed_regs will keep the
   compiler's mitts completely off it.  We don't bother to zero it out
   of register classes.  Also fix incompatible register naming with
   the UNIX assembler.  */

static void
pdp11_conditional_register_usage (void)
{
  int i;
  HARD_REG_SET x;
  if (!TARGET_FPU)
    {
      x = reg_class_contents[FPU_REGS];
      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++ )
       if (TEST_HARD_REG_BIT (x, i))
	fixed_regs[i] = call_used_regs[i] = 1;
    }

  if (TARGET_AC0)
      call_used_regs[AC0_REGNUM] = 1;
  if (TARGET_UNIX_ASM)
    {
      /* Change names of FPU registers for the UNIX assembler.  */
      reg_names[8] = "fr0";
      reg_names[9] = "fr1";
      reg_names[10] = "fr2";
      reg_names[11] = "fr3";
      reg_names[12] = "fr4";
      reg_names[13] = "fr5";
    }
}

static section *
pdp11_function_section (tree decl ATTRIBUTE_UNUSED,
			enum node_frequency freq ATTRIBUTE_UNUSED,
			bool startup ATTRIBUTE_UNUSED,
			bool exit ATTRIBUTE_UNUSED)
{
  return NULL;
}

/* Support #ident for DEC assembler, but don't process the
   auto-generated ident string that names the compiler (since its
   syntax is not correct for DEC .ident).  */
static void pdp11_output_ident (const char *ident)
{
  if (TARGET_DEC_ASM)
    {
      if (!startswith (ident, "GCC:"))
	fprintf (asm_out_file, "\t.ident\t\"%s\"\n", ident);
    }
  
}

/* This emits a (user) label, which gets a "_" prefix except for DEC
   assembler output.  */
void
pdp11_output_labelref (FILE *file, const char *name)
{
  if (!TARGET_DEC_ASM)
    fputs (USER_LABEL_PREFIX, file);
  fputs (name, file);
}

/* This equates name with value.  */
void
pdp11_output_def (FILE *file, const char *label1, const char *label2)
{
  if (TARGET_DEC_ASM)
    {
      assemble_name (file, label1);
      putc ('=', file);
      assemble_name (file, label2);
    }
  else
    {
      fputs ("\t.set\t", file);
      assemble_name (file, label1);
      putc (',', file);
      assemble_name (file, label2);
    } 
  putc ('\n', file);
}

void
pdp11_output_addr_vec_elt (FILE *file, int value)
{
  char buf[256];

  pdp11_gen_int_label (buf, "L", value);
  if (!TARGET_UNIX_ASM)
    fprintf (file, "\t.word");
  fprintf (file, "\t%s\n", buf + 1);
}

/* This overrides some target hooks that are initializer elements so
   they can't be variables in the #define.  */
static void
pdp11_option_override (void)
{
  if (TARGET_DEC_ASM)
    {
      targetm.asm_out.open_paren  = "<";
      targetm.asm_out.close_paren = ">";
    }
}

static void
pdp11_asm_named_section (const char *name, unsigned int flags,
			 tree decl ATTRIBUTE_UNUSED)
{
  const char *rwro = (flags & SECTION_WRITE) ? "rw" : "ro";
  const char *insdat = (flags & SECTION_CODE) ? "i" : "d";
  
  gcc_assert (TARGET_DEC_ASM);
  fprintf (asm_out_file, "\t.psect\t%s,con,%s,%s\n", name, insdat, rwro);
}

static void
pdp11_asm_init_sections (void)
{
  if (TARGET_DEC_ASM)
    {
      bss_section = data_section;
    }
  else if (TARGET_GNU_ASM)
    {
      bss_section = get_unnamed_section (SECTION_WRITE | SECTION_BSS,
					 output_section_asm_op,
					 ".bss");
    }
}
  
static void
pdp11_file_start (void)
{
  default_file_start ();
  
  if (TARGET_DEC_ASM)
    fprintf (asm_out_file, "\t.enabl\tlsb,reg\n\n");
}

static void
pdp11_file_end (void)
{
  if (TARGET_DEC_ASM)
    fprintf (asm_out_file, "\t.end\n");
}

/* Implement TARGET_LEGITIMATE_CONSTANT_P.  */

static bool
pdp11_legitimate_constant_p (machine_mode mode ATTRIBUTE_UNUSED, rtx x)
{
  return GET_CODE (x) != CONST_DOUBLE || legitimate_const_double_p (x);
}

/* Implement TARGET_SCALAR_MODE_SUPPORTED_P.  */

static bool
pdp11_scalar_mode_supported_p (scalar_mode mode)
{
  /* Support SFmode even with -mfloat64.  */
  if (mode == SFmode)
    return true;
  return default_scalar_mode_supported_p (mode);
}

/* Implement TARGET_HARD_REGNO_NREGS.  */

static unsigned int
pdp11_hard_regno_nregs (unsigned int regno, machine_mode mode)
{
  if (regno <= PC_REGNUM)
    return CEIL (GET_MODE_SIZE (mode), UNITS_PER_WORD);
  return 1;
}

/* Implement TARGET_HARD_REGNO_MODE_OK.  On the pdp, the cpu registers
   can hold any mode other than float (because otherwise we may end up
   being asked to move from CPU to FPU register, which isn't a valid
   operation on the PDP11).  For CPU registers, check alignment.

   FPU accepts SF and DF but actually holds a DF - simplifies life!  */

static bool
pdp11_hard_regno_mode_ok (unsigned int regno, machine_mode mode)
{
  if (regno <= PC_REGNUM)
    return (GET_MODE_BITSIZE (mode) <= 16
	    || (GET_MODE_BITSIZE (mode) >= 32
		&& !(regno & 1)
		&& !FLOAT_MODE_P (mode)));

  return FLOAT_MODE_P (mode);
}

/* Implement TARGET_MODES_TIEABLE_P.  */

static bool
pdp11_modes_tieable_p (machine_mode mode1, machine_mode mode2)
{
  return mode1 == HImode && mode2 == QImode;
}

/* Implement PUSH_ROUNDING.  On the pdp11, the stack is on an even
   boundary.  */

poly_int64
pdp11_push_rounding (poly_int64 bytes)
{
  return (bytes + 1) & ~1;
}

struct gcc_target targetm = TARGET_INITIALIZER;