subsegs.c

早期freebsd实现

/* subsegs.c - subsegments -
   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.  */

/*
 * Segments & sub-segments.
 */

#include "as.h"
#include "subsegs.h"
#include "obstack.h"
#include "frags.h"
#include "struc-symbol.h"
#include "write.h"

frchainS*	frchain_root,
	*	frchain_now,	/* Commented in "subsegs.h". */
	*	data0_frchainP;


const int				/* in: segT   out: N_TYPE bits */
seg_N_TYPE[] = {
  N_ABS,
  N_TEXT,
  N_DATA,
  N_BSS,
  N_UNDF,
  N_UNDF,
  N_UNDF,
  N_UNDF,
  N_UNDF,
  N_UNDF
};


char * const				/* in: segT   out: char* */
seg_name[] = {
  "absolute",
  "text",
  "data",
  "bss",
  "unknown",
  "absent",
  "pass1",
  "ASSEMBLER-INTERNAL-LOGIC-ERROR!",
  "bignum/flonum",
  "difference",
  ""
  };				/* Used by error reporters, dumpers etc. */

const segT N_TYPE_seg [N_TYPE+2] =	/* N_TYPE == 0x1E = 32-2 */
{
  SEG_UNKNOWN,			/* N_UNDF == 0 */
  SEG_GOOF,
  SEG_ABSOLUTE,			/* N_ABS == 2 */
  SEG_GOOF,
  SEG_TEXT,			/* N_TEXT == 4 */
  SEG_GOOF,
  SEG_DATA,			/* N_DATA == 6 */
  SEG_GOOF,
  SEG_BSS,			/* N_BSS == 8 */
  SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF,
  SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF,
  SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF, SEG_GOOF
};

void
subsegs_begin()
{
  /* Check table(s) seg_name[], seg_N_TYPE[] is in correct order */
  know( SEG_ABSOLUTE	==0 );
  know( SEG_TEXT    	==1 );
  know( SEG_DATA    	==2 );
  know( SEG_BSS     	==3 );
  know( SEG_UNKNOWN 	==4 );
  know( SEG_NONE    	==5 );
  know( SEG_PASS1	==6 );
  know( SEG_GOOF	==7 );
  know( SEG_BIG		==8 );
  know( SEG_DIFFERENCE	==9 );
  know( SEG_MAXIMUM_ORDINAL == SEG_DIFFERENCE );
  know( seg_name [(int) SEG_MAXIMUM_ORDINAL + 1] [0] == 0 );

  obstack_begin( &frags, 5000);
  frchain_root = NULL;
  frchain_now  = NULL;		/* Warn new_subseg() that we are booting. */
				/* Fake up 1st frag. */
				/* It won't be used=> is ok if obstack... */
				/* pads the end of it for alignment. */
  frag_now=(fragS *)obstack_alloc(&frags,SIZEOF_STRUCT_FRAG);
  /* obstack_1blank( &frags, SIZEOF_STRUCT_FRAG, & frag_now ); */
				/* This 1st frag will not be in any frchain. */
				/* We simply give subseg_new somewhere to scribble. */
  now_subseg = 42;		/* Lie for 1st call to subseg_new. */
  subseg_new (SEG_DATA, 0);	/* .data 0 */
  data0_frchainP = frchain_now;
}

/*
 *			subseg_change()
 *
 * Change the subsegment we are in, BUT DO NOT MAKE A NEW FRAG for the
 * subsegment. If we are already in the correct subsegment, change nothing.
 * This is used eg as a worker for subseg_new [which does make a new frag_now]
 * and for changing segments after we have read the source. We construct eg
 * fixSs even after the source file is read, so we do have to keep the
 * segment context correct.
 */
void
subseg_change (seg, subseg)
     register segT	seg;
     register int	subseg;
{
  now_seg	 = seg;
  now_subseg = subseg;
  if (seg == SEG_DATA)
    {
      seg_fix_rootP = & data_fix_root;
    }
  else
    {
      know (seg == SEG_TEXT);
      seg_fix_rootP = & text_fix_root;
    }
}

/*
 *			subseg_new()
 *
 * If you attempt to change to the current subsegment, nothing happens.
 *
 * In:	segT, subsegT code for new subsegment.
 *	frag_now -> incomplete frag for current subsegment.
 *	If frag_now==NULL, then there is no old, incomplete frag, so
 *	the old frag is not closed off.
 *
 * Out:	now_subseg, now_seg updated.
 *	Frchain_now points to the (possibly new) struct frchain for this
 *	sub-segment.
 *	Frchain_root updated if needed.
 */

void
subseg_new (seg, subseg)	/* begin assembly for a new sub-segment */
     register segT	seg;	/* SEG_DATA or SEG_TEXT */
     register subsegT	subseg;
{
  long tmp;		/* JF for obstack alignment hacking */

  know( seg == SEG_DATA || seg == SEG_TEXT );

  if (seg != now_seg || subseg != now_subseg)
    {				/* we just changed sub-segments */
      register	frchainS *	frcP;	/* crawl frchain chain */
      register	frchainS**	lastPP;	/* address of last pointer */
		frchainS *	newP;	/* address of new frchain */
      register fragS *		former_last_fragP;
      register fragS *		new_fragP;

      if (frag_now)		/* If not bootstrapping. */
	{
	  frag_now -> fr_fix = obstack_next_free(& frags) - frag_now -> fr_literal;
	  frag_wane(frag_now);	/* Close off any frag in old subseg. */
	}
/*
 * It would be nice to keep an obstack for each subsegment, if we swap
 * subsegments a lot. Hence we would have much fewer frag_wanes().
 */
      {

	obstack_finish( &frags);
	/*
	 * If we don't do the above, the next object we put on obstack frags
	 * will appear to start at the fr_literal of the current frag.
	 * Also, above ensures that the next object will begin on a
	 * address that is aligned correctly for the engine that runs
	 * this program.
	 */
      }
      subseg_change (seg, (int)subseg);
      /*
       * Attempt to find or make a frchain for that sub seg.
       * Crawl along chain of frchainSs, begins @ frchain_root.
       * If we need to make a frchainS, link it into correct
       * position of chain rooted in frchain_root.
       */
      for (frcP = * (lastPP = & frchain_root);
	   frcP
	   && (int)(frcP -> frch_seg) <= (int)seg;
	   frcP = * ( lastPP = & frcP -> frch_next)
	  )
	{
	  if (   (int)(frcP -> frch_seg) == (int)seg
	      && frcP -> frch_subseg >= subseg)
	    {
	      break;
	    }
	}
      /*
       * frcP:		Address of the 1st frchainS in correct segment with
       *		frch_subseg >= subseg.
       *		We want to either use this frchainS, or we want
       *		to insert a new frchainS just before it.
       *
       *		If frcP==NULL, then we are at the end of the chain
       *		of frchainS-s. A NULL frcP means we fell off the end
       *		of the chain looking for a
       *		frch_subseg >= subseg, so we
       *		must make a new frchainS.
       *
       *		If we ever maintain a pointer to
       *		the last frchainS in the chain, we change that pointer
       *		ONLY when frcP==NULL.
       *
       * lastPP:	Address of the pointer with value frcP;
       *		Never NULL.
       *		May point to frchain_root.
       *
       */
      if (   ! frcP
	  || (   (int)(frcP -> frch_seg) > (int)seg
	      || frcP->frch_subseg > subseg)) /* Kinky logic only works with 2 segments. */
	{
	  /*
	   * This should be the only code that creates a frchainS.
	   */
	  newP=(frchainS *)obstack_alloc(&frags,sizeof(frchainS));
	  /* obstack_1blank( &frags, sizeof(frchainS), &newP); */
				/* This begines on a good boundary */
				/* because a obstack_done() preceeded  it. */
				/* It implies an obstack_done(), so we */
				/* expect the next object allocated to */
				/* begin on a correct boundary. */
	  *lastPP = newP;
	  newP -> frch_next = frcP; /* perhaps NULL */
	  (frcP = newP) -> frch_subseg		= subseg;
		  newP  -> frch_seg		= seg;
		  newP  -> frch_last	 	= NULL;
	}
      /*
       * Here with frcP ->ing to the frchainS for subseg.
       */
      frchain_now = frcP;
      /*
       * Make a fresh frag for the subsegment.
       */
				/* We expect this to happen on a correct */
				/* boundary since it was proceeded by a */
				/* obstack_done(). */
      tmp=obstack_alignment_mask(&frags);	/* JF disable alignment */
      obstack_alignment_mask(&frags)=0;
      frag_now=(fragS *)obstack_alloc(&frags,SIZEOF_STRUCT_FRAG);
      obstack_alignment_mask(&frags)=tmp;
      /* know( frags . obstack_c_next_free == frag_now -> fr_literal ); */
				/* But we want any more chars to come */
				/* immediately after the structure we just made. */
      new_fragP = frag_now;
      new_fragP -> fr_next = NULL;
      /*
       * Append new frag to current frchain.
       */
      former_last_fragP = frcP -> frch_last;
      if (former_last_fragP)
	{
	  know( former_last_fragP -> fr_next == NULL );
	  know( frchain_now -> frch_root );
	  former_last_fragP -> fr_next = new_fragP;
	}
      else
	{
	  frcP -> frch_root = new_fragP;
	}
      frcP -> frch_last = new_fragP;
    }				/* if (changing subsegments) */
}				/* subseg_new() */

/* end: subsegs.c */