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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.
*/


/**********************************************************************
$Author: release $
$Date: 1998/01/17 15:56:05 $
$Revision: 1.1.1.1 $
$Log: getregs.c,v $
 * Revision 1.1.1.1  1998/01/17  15:56:05  release
 * First version to be checked into rolling release.
 *
 * Revision 1.1  1995/04/13  09:08:06  currie
 * Initial revision
 *
***********************************************************************/
/******************************************************************
                getregs.c

        Routines for choosing temporary registers. The next free
register is chosen cyclically from the registers 8-15, 24 and 25 for
fixed point and 4-10 and 16-18 in floating point (a factor of 2 is involved here) by examining the bit pattern of the parameter. If the current proc allows it, regs 4-7 may also be used as t-regs - this is the function of chooseafter25 etc. The parameter is usuallytaken from a value of type
 space (which has bits for fixed and floating regs).
A clear bit indicates that the corresponding register is free for use.

******************************************************************/
#include "config.h"
#include "common_types.h"
#include "procrectypes.h"
#include "exptypes.h"
#include "expmacs.h"
#include "exp.h"
#include "regexps.h"
#include "tags.h"
#include "expmacs.h"
#include "bitsmacs.h"
#include "flags.h"
#include "getregs.h"
#include "basicread.h"

extern  procrec * procrecs;
static long useable_fixed;
static long useable_float;

#define for8  0x100             /* bit pattern for $8,  bit 9 is set */
#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


long  choosefix = for8;         /* first fixed reg to be allocated */
long  choosefloat = for0;       /* first float reg to be allocated */

int   currentfix = 8;
int   currentfloat = 2;
static int   maxfixed;
static int   maxfloat = 9;
static int minfixed;
static long formin;


void settempregs
    PROTO_N ( (tg) )
    PROTO_T ( exp tg )
{
                                /* tg is a proc; 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
                                    regs 4-7 */
  procrec * pr = &procrecs[no(tg)];
  bool leaf = ((pr->needsproc).propsneeds & anyproccall)==0;
  exp stg = son(tg);
  currentfix = 8;
  currentfloat = 0;
  choosefix = for8;
  choosefloat = for0;
  useable_fixed = 0x8300fffc;
        /* r31 (lnk) /r24-25/ r8-r15/ r4-r7 (pars) /r2-r3*/
  useable_float = 0x3ff;        /* f0-f2 (resreg) f4-f10 f12-f14 (pars)
                                        f16-f18*/
  if (leaf) {
        useable_fixed &= ~0x80000000;
        maxfixed = 25;
  }
  else maxfixed = 31;

  if (PIC_code) {
        useable_fixed &= ~0x02000000;
        if (maxfixed==25) maxfixed = 24;
  }

  if (((pr->needsproc).propsneeds & uses2_bit) != 0) {
        useable_fixed &= ~0x4;
        minfixed = 3;
        formin = 0x8;
  }
  else {
        minfixed = 2;
        formin = 0x4;
  }

  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));
  }

}

int   getreg
    PROTO_N ( (fixed) )
    PROTO_T ( long fixed )
{       /* get a free temporary fixed pt reg */
  int   reg = -1;
  long  start = choosefix;


  for (;;) {
    if ((choosefix & fixed) == 0) {
      reg = currentfix;
    }
  cycle:
    if (currentfix >= maxfixed) {
        currentfix = minfixed;
        choosefix = formin;
    }
    else {
      currentfix +=1;
      choosefix <<= 1;
    }

    if ((choosefix & useable_fixed) != 0) {
        if (reg >=0) break;
        else continue;
    }
    if (choosefix == start) {
        failer("Too many fixed regs required");
                break;
    }
    goto cycle;
  }
  return reg;
}


int   getfreg
    PROTO_N ( (fl) )
    PROTO_T ( long fl )
{       /* get a free temporary floating reg */
  int   reg = -1;
  long  start = choosefloat;

  for (;;) {
    if ((choosefloat & fl) == 0) {
      reg = currentfloat;
    }
  cycle:
    if (currentfloat >= maxfloat) {
        currentfloat = 0;
        choosefloat = for0;
    }
    else {
      currentfloat +=1;
      choosefloat <<= 1;
    }

    if ((choosefloat & useable_float) != 0) {
        if (reg >=0) break;
        else continue;
    }
    if (choosefloat == start) {
        failer("Too many float regs required");
                break;
    }
    goto cycle;
  }
  return reg;
}