vax.c

早期freebsd实现

/* vax.c - vax-specific -
   Copyright (C) 1987 Free Software Foundation, Inc.

This file is part of GAS, the GNU Assembler.

GAS 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 1, or (at your option)
any later version.

GAS 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 GAS; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* JF I moved almost all the vax specific stuff into this one file 'cuz RMS
   seems to think its a good idea.  I hope I managed to get all the VAX-isms */


#include "as.h"
#include "read.h"
#include "flonum.h"
#include "vax-inst.h"
#include "md.h"
#include "obstack.h"		/* For FRAG_APPEND_1_CHAR macro in "frags.h" */
#include "frags.h"
#include "struc-symbol.h"
#include "expr.h"
#include "symbols.h"

/* This is the number to put at the beginning of the a.out file */
long omagic = OMAGIC;

/* These chars start a comment anywhere in a source file (except inside
   another comment */
const char comment_chars[] = "#";

/* These chars only start a comment at the beginning of a line. */
/* Note that for the VAX the are the same as comment_chars above. */
const char line_comment_chars[] = "#";

/* Chars that can be used to separate mant from exp in floating point nums */
const char EXP_CHARS[] = "eE";

/* Chars that mean this number is a floating point constant */
/* as in 0f123.456 */
/* or    0H1.234E-12 (see exp chars above) */
const char FLT_CHARS[] = "dDfFgGhH";

/* Also be aware that MAXIMUM_NUMBER_OF_CHARS_FOR_FLOAT may have to be
   changed in read.c .  Ideally it shouldn't have to know about it at all,
   but nothing is ideal around here.
 */

static expressionS		/* Hold details of an operand expression */
 exp_of_operand[VIT_MAX_OPERANDS];

static struct vit
 v;				/* A vax instruction after decoding. */

LITTLENUM_TYPE big_operand_bits[VIT_MAX_OPERANDS][SIZE_OF_LARGE_NUMBER];
 /* Hold details of big operands. */
FLONUM_TYPE float_operand[VIT_MAX_OPERANDS];
 /* Above is made to point into */
 /* big_operand_bits by md_begin(). */

/*
 * For VAX, relative addresses of "just the right length" are easy.
 * The branch displacement is always the last operand, even in
 * synthetic instructions.
 * For VAX, we encode the relax_substateTs (in e.g. fr_substate) as:
 *
 *		    4       3       2       1       0	     bit number
 *	---/ /--+-------+-------+-------+-------+-------+
 *		|     what state ?	|  how long ?	|
 *	---/ /--+-------+-------+-------+-------+-------+
 *
 * The "how long" bits are 00=byte, 01=word, 10=long.
 * This is a Un*x convention.
 * Not all lengths are legit for a given value of (what state).
 * The "how long" refers merely to the displacement length.
 * The address usually has some constant bytes in it as well.
 *

groups for VAX address relaxing.

1.	"foo" pc-relative.
	length of byte, word, long

2a.	J<cond> where <cond> is a simple flag test.
	length of byte, word, long.
	VAX opcodes are:	(Hex)
		bneq/bnequ	12
		beql/beqlu	13
		bgtr		14
		bleq		15
		bgeq		18
		blss		19
		bgtru		1a
		blequ		1b
		bvc		1c
		bvs		1d
		bgequ/bcc	1e
		blssu/bcs	1f
	Always, you complement 0th bit to reverse condition.
	Always, 1-byte opcode, then 1-byte displacement.

2b.	J<cond> where cond tests a memory bit.
	length of byte, word, long.
	Vax opcodes are:	(Hex)
		bbs		e0
		bbc		e1
		bbss		e2
		bbcs		e3
		bbsc		e4
		bbcc		e5
		bbssi		e6
		bbcci		e7
	Always, you complement 0th bit to reverse condition.
	Always, 1-byte opcde, longword-address, byte-address, 1-byte-displacement

2c.	J<cond> where cond tests low-order memory bit
	length of byte,word,long.
	Vax opcodes are:	(Hex)
		blbs		e8
		blbc		e9
	Always, you complement 0th bit to reverse condition.
	Always, 1-byte opcode, longword-address, 1-byte displacement.

3.	Jbs/Jbr.
	length of byte,word,long.
	Vax opcodes are:	(Hex)
		bsbb		10
		brb		11
	These are like (2) but there is no condition to reverse.
	Always, 1 byte opcode, then displacement/absolute.

4a.	JacbX
	length of word, long.
	Vax opcodes are:	(Hex)
		acbw		3d
		acbf		4f
		acbd		6f
		abcb		9d
		acbl		f1
		acbg	      4ffd
		acbh	      6ffd
	Always, we cannot reverse the sense of the branch; we have a word
	displacement.
	The double-byte op-codes don't hurt: we never want to modify the
	opcode, so we don't care how many bytes are between the opcode and
	the operand.

4b.	JXobXXX
	length of long, long, byte.
	Vax opcodes are:	(Hex)
		aoblss		f2
		aobleq		f3
		sobgeq		f4
		sobgtr		f5
	Always, we cannot reverse the sense of the branch; we have a byte
	displacement.

The only time we need to modify the opcode is for class 2 instructions.
After relax() we may complement the lowest order bit of such instruction
to reverse sense of branch.

For class 2 instructions, we store context of "where is the opcode literal".
We can change an opcode's lowest order bit without breaking anything else.

We sometimes store context in the operand literal. This way we can figure out
after relax() what the original addressing mode was.
*/

 /* These displacements are relative to */
 /* the start address of the displacement. */
 /* The first letter is Byte, Word. */
 /* 2nd letter is Forward, Backward. */
#define BF (1+ 127)
#define BB (1+-128)
#define WF (2+ 32767)
#define WB (2+-32768)
 /* Dont need LF, LB because they always */
 /* reach. [They are coded as 0.] */


#define C(a,b) ENCODE_RELAX(a,b)
 /* This macro has no side-effects. */
#define ENCODE_RELAX(what,length) (((what) << 2) + (length))

const relax_typeS
md_relax_table[] =
{
  {
    1, 1, 0, 0
  },				/* error sentinel   0,0	*/
  {
    1, 1, 0, 0
  },				/* unused	    0,1	*/
  {
    1, 1, 0, 0
  },				/* unused	    0,2	*/
  {
    1, 1, 0, 0
  },				/* unused	    0,3	*/
  {
    BF + 1, BB + 1, 2, C (1, 1)
  },				/* B^"foo"	    1,0 */
  {
    WF + 1, WB + 1, 3, C (1, 2)
  },				/* W^"foo"	    1,1 */
  {
    0, 0, 5, 0
  },				/* L^"foo"	    1,2 */
  {
    1, 1, 0, 0
  },				/* unused	    1,3 */
  {
    BF, BB, 1, C (2, 1)
  },				/* b<cond> B^"foo"  2,0 */
  {
    WF + 2, WB + 2, 4, C (2, 2)
  },				/* br.+? brw X	    2,1 */
  {
    0, 0, 7, 0
  },				/* br.+? jmp X	    2,2 */
  {
    1, 1, 0, 0
  },				/* unused	    2,3 */
  {
    BF, BB, 1, C (3, 1)
  },				/* brb B^foo	    3,0 */
  {
    WF, WB, 2, C (3, 2)
  },				/* brw W^foo	    3,1 */
  {
    0, 0, 5, 0
  },				/* Jmp L^foo	    3,2 */
  {
    1, 1, 0, 0
  },				/* unused	    3,3 */
  {
    1, 1, 0, 0
  },				/* unused	    4,0 */
  {
    WF, WB, 2, C (4, 2)
  },				/* acb_ ^Wfoo	    4,1 */
  {
    0, 0, 10, 0
  },				/* acb_,br,jmp L^foo4,2 */
  {
    1, 1, 0, 0
  },				/* unused	    4,3 */
  {
    BF, BB, 1, C (5, 1)
  },				/* Xob___,,foo      5,0 */
  {
    WF + 4, WB + 4, 6, C (5, 2)
  },				/* Xob.+2,brb.+3,brw5,1 */
  {
    0, 0, 9, 0
  },				/* Xob.+2,brb.+6,jmp5,2 */
};

#undef C
#undef BF
#undef BB
#undef WF
#undef WB

void float_cons ();

const pseudo_typeS md_pseudo_table[] =
{
  {"dfloat", float_cons, 'd'},
  {"ffloat", float_cons, 'f'},
  {"gfloat", float_cons, 'g'},
  {"hfloat", float_cons, 'h'},
  {0}
};

#define STATE_PC_RELATIVE		(1)
#define STATE_CONDITIONAL_BRANCH	(2)
#define STATE_ALWAYS_BRANCH		(3)	/* includes BSB... */
#define STATE_COMPLEX_BRANCH	        (4)
#define STATE_COMPLEX_HOP		(5)

#define STATE_BYTE			(0)
#define STATE_WORD			(1)
#define STATE_LONG			(2)
#define STATE_UNDF			(3)	/* Symbol undefined in pass1 */


#define min(a, b)	((a) < (b) ? (a) : (b))


void
md_begin ()
{
  char *vip_begin ();
  char *errtxt;
  FLONUM_TYPE *fP;
  int i;

  if (*(errtxt = vip_begin (TRUE, "$", "*", "`")))
    {
      as_fatal ("VIP_BEGIN error:%s", errtxt);
    }

  for (i = 0, fP = float_operand;
       fP < float_operand + VIT_MAX_OPERANDS;
       i++, fP++)
    {
      fP->low = &big_operand_bits[i][0];
      fP->high = &big_operand_bits[i][SIZE_OF_LARGE_NUMBER - 1];
    }
}

void
md_end ()
{
  vip_end ();
}

void				/* Knows about order of bytes in address. */
md_number_to_chars (con, value, nbytes)
     char con[];		/* Return 'nbytes' of chars here. */
     long int value;		/* The value of the bits. */
     int nbytes;		/* Number of bytes in the output. */
{
  int n;
  long v;

  n = nbytes;
  v = value;
  while (nbytes--)
    {
      *con++ = value;		/* Lint wants & MASK_CHAR. */
      value >>= BITS_PER_CHAR;
    }
  /* XXX line number probably botched for this warning message. */
  if (value != 0 && value != -1)
    as_warn ("Displacement (%ld) long for instruction field length (%d).", v, n);
}

void				/* Knows about order of bytes in address. */
md_number_to_imm (con, value, nbytes)
     char con[];		/* Return 'nbytes' of chars here. */
     long int value;		/* The value of the bits. */
     int nbytes;		/* Number of bytes in the output. */
{
  int n;
  long v;

  n = nbytes;
  v = value;
  while (nbytes--)
    {
      *con++ = value;		/* Lint wants & MASK_CHAR. */
      value >>= BITS_PER_CHAR;
    }
  /* XXX line number probably botched for this warning message. */
  if (value != 0 && value != -1)
    as_warn ("Displacement (%ld) too long for instruction field length (%d).", v, n);
}

void				/* Knows about order of bytes in address. */
md_number_to_disp (con, value, nbytes)
     char con[];		/* Return 'nbytes' of chars here. */
     long int value;		/* The value of the bits. */
     int nbytes;		/* Number of bytes in the output. */
{
  abort ();
  while (nbytes--)
    {
      *con++ = value;		/* Lint wants & MASK_CHAR. */
      value >>= BITS_PER_CHAR;
    }
  /* XXX line number probably botched for this warning message. */
  if (value != 0 && value != -1)
    as_warn ("Displacement too long for instruction field length.");
}

void				/* Knows about order of bytes in address. */
md_number_to_field (con, value, nbytes)
     char con[];		/* Return 'nbytes' of chars here. */
     long int value;		/* The value of the bits. */
     int nbytes;		/* Number of bytes in the output. */
{
  abort ();
  while (nbytes--)
    {
      *con++ = value;		/* Lint wants & MASK_CHAR. */
      value >>= BITS_PER_CHAR;
    }
  /* XXX line number probably botched for this warning message. */
  if (value != 0 && value != -1)
    as_warn ("Displacement too long for instruction field length.");
}

long int			/* Knows about the byte order in a word. */
md_chars_to_number (con, nbytes)
     unsigned char con[];	/* Low order byte 1st. */
     int nbytes;		/* Number of bytes in the input. */
{
  long int retval;
  for (retval = 0, con += nbytes - 1; nbytes--; con--)
    {
      retval <<= BITS_PER_CHAR;
      retval |= *con;
    }
  return retval;
}

/* vax:md_assemble() emit frags for 1 instruction */

void
md_assemble (instruction_string)
     char *instruction_string;	/* A string: assemble 1 instruction. */
{
  char *p;
  register struct vop *operandP;/* An operand. Scans all operands. */
  char *save_input_line_pointer;
  char c_save;			/* What used to live after an expression. */
  struct frag *fragP;		/* Fragment of code we just made. */
  register int goofed;		/* TRUE: instruction_string bad for all passes. */
  register struct vop *end_operandP;	/* -> slot just after last operand */
  /* Limit of the for (each operand). */
  register expressionS *expP;	/* -> expression values for this operand */

  /* These refer to an instruction operand expression. */
  segT to_seg;			/* Target segment of the address.	 */
  register valueT this_add_number;
  register struct symbol *this_add_symbol;	/* +ve (minuend) symbol. */
  register struct symbol *this_subtract_symbol;	/* -ve(subtrahend) symbol. */

  long int opcode_as_number;	/* As a number. */
  char *opcode_as_chars;	/* Least significant byte 1st. */
  /* As an array of characters. */
  char *opcode_low_byteP;	/* Least significant byte 1st */
  struct details *detP;		/* The details of an ADxxx frag. */