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/*
                 Crown Copyright (c) 1997
    
    This TenDRA(r) Computer Program is subject to Copyright
    owned by the United Kingdom Secretary of State for Defence
    acting through the Defence Evaluation and Research Agency
    (DERA).  It is made available to Recipients with a
    royalty-free licence for its use, reproduction, transfer
    to other parties and amendment for any purpose not excluding
    product development provided that any such use et cetera
    shall be deemed to be acceptance of the following conditions:-
    
        (1) Its Recipients shall ensure that this Notice is
        reproduced upon any copies or amended versions of it;
    
        (2) Any amended version of it shall be clearly marked to
        show both the nature of and the organisation responsible
        for the relevant amendment or amendments;
    
        (3) Its onward transfer from a recipient to another
        party shall be deemed to be that party's acceptance of
        these conditions;
    
        (4) DERA gives no warranty or assurance as to its
        quality or suitability for any purpose and DERA accepts
        no liability whatsoever in relation to any use to which
        it may be put.
*/


/*      $Id: getregs.c,v 1.1.1.1 1998/01/17 15:56:00 release Exp $       */

#ifndef lint
static char vcid[] = "$Id: getregs.c,v 1.1.1.1 1998/01/17 15:56:00 release Exp $";
#endif /* lint */

/*
  getregs.c
*/

/*
$Log: getregs.c,v $
 * Revision 1.1.1.1  1998/01/17  15:56:00  release
 * First version to be checked into rolling release.
 *
 * Revision 1.6  1995/11/13  12:43:05  john
 * Changed register allocation
 *
 * Revision 1.5  1995/10/27  12:42:28  john
 * changed to allow use of result reg
 *
 * Revision 1.4  1995/08/04  15:50:27  john
 * Minor change
 *
 * Revision 1.3  1995/07/27  10:08:04  john
 * Fix to choosefix
 *
 * Revision 1.2  1995/05/16  10:48:58  john
 * Cosmetic changes
 *
 * Revision 1.1.1.1  1995/03/23  10:39:09  john
 * Entered into CVS
 *
 * Revision 1.6  1995/01/12  15:07:53  john
 * Changed error reporting
 *
*/


#include "config.h"
#include "common_types.h"
#include "procrectypes.h"
#include "exptypes.h"
#include "procrecs.h"
#include "expmacs.h"
#include "exp.h"
#include "regexps.h"
#include "tags.h"
#include "expmacs.h"
#include "bitsmacs.h"
#include "fail.h"
#include "getregs.h"

static int useable_fixed;
static int useable_float;

#define for1  0x002     
#define for2  0x004
#define for8  0x100     /* bit pattern for $8,  bit 9 is set */
#define for10 0x400     /* bit pattern for $10, bit 11 set */
#define for11 0x800
#define for15 0x8000    /* bit pattern for $15, bit 16 is set */
#define for24 0x1000000         /* etc ... */
#define for25 0x2000000

#define for0  0x1
#define for4  0x10
#define for5  0x20
#define for9  0x200


static int regs_corrupted_by_div = (1<<23)|(1<<24)|(1<<25)|(1<<27);



int  choosefix = for1;          /* first fixed reg to be allocated */
int  choosefloat = for1;        /* first float reg to be allocated */

int   currentfix = 1;
int   currentfloat = 1;
static int   maxfixed;
static int   maxfloat = 31;     /* dubious */

/* 
   tg is a proc. settempregs sets up useable_fixed etc depending 
   on how the proc treats its parameters; if they are destined for
   store or s-registers we can use some of the parameter registers 
*/
void settempregs
    PROTO_N ( ( tg ) )
    PROTO_T ( exp tg )
{
  procrec * pr = &procrecs[no(tg)];
  bool leaf = ((pr->needsproc).propsneeds & anyproccall)==0;
  exp stg = son(tg);
  currentfix = 1;
  currentfloat = 1;
  choosefix = for1;
  choosefloat = for1;
  useable_fixed = 0x03ff01ff;   /* leaves out parameter registers */
  useable_float = 0x7fc0fc00;
  if(has_machine_division(tg)){
    useable_fixed &= ~regs_corrupted_by_div;
  }
  if (leaf) {
    maxfixed=31;
  }
  else maxfixed = 31;
  
  while (name(stg)==ident_tag && isparam(stg)) {
    if ((props(stg) & inreg_bits) !=0 ) {
      useable_fixed &= ~ (1<<no(stg));
    }
    else
      if ((props(stg) & infreg_bits) != 0) {
        useable_float &= ~(1<<no(stg));
      }
    stg = bro(son(stg));
  }
  return;
}

/*
  Gets a free temporary fixed point register.  The int fixed masks 
  out registers which are not available.
*/
int getreg
    PROTO_N ( ( fixed ) )
    PROTO_T ( int32 fixed )
{
  int reg=-1;
  int start = choosefix;
  bool out_of_regs=0;
  for(;(!out_of_regs)&&(reg==-1);){
    if(currentfix>=maxfixed){
      currentfix=1;
      choosefix=for1;
    }
    else{
      currentfix++;
      choosefix<<=1;
    }
    if(!(choosefix&fixed) && (choosefix&useable_fixed)){
      reg = currentfix;
    }
    out_of_regs = (reg==-1)&&(choosefix==start);
  }
  if(out_of_regs){
    alphafail(OUT_OF_TREGS);
  }
  clear_reg(reg);
  return reg;
}


/*
  Get a free temporary floating point register.
*/
int getfreg
    PROTO_N ( ( fl ) )
    PROTO_T ( int fl )
{
  int freg=-1;
  int start = choosefloat;
  bool out_of_regs=0;
  for(;(!out_of_regs)&&(freg==-1);){
    if(currentfloat>=maxfloat){
      currentfloat=10;
      choosefloat=for10;
    }
    else{
      currentfloat++;
      choosefloat<<=1;
    }
    if(!(choosefloat&fl) && (choosefloat&useable_float)){
      freg = currentfloat;
    }
    out_of_regs = (freg==-1)&&(choosefloat==start);
  }
  if(out_of_regs){
    alphafail(OUT_OF_F_TREGS);
  }
  return freg;
}