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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.

*/

/*

$Log: regexps.c,v $

 * Revision 1.1.1.1  1998/01/17  15:56:03  release

 * First version to be checked into rolling release.

 *

 * Revision 1.4  1996/11/14  15:22:26  wfs

 *    Fixed a bug in regexps.c which was common to most of the installers and

 * has only just come to light due to PWE's work on powertrans. (There was

 * previously only a patch.) Cosmetic changes to other files.

 *

 * Revision 1.3  1996/01/23  15:26:07  wfs

 * "current_env_tag" in "dependson()".

 *

 * Revision 1.2  1995/12/18  13:12:30  wfs

 * Put hppatrans uder cvs control. Major Changes made since last release

 * include:

 * (i) PIC code generation.

 * (ii) Profiling.

 * (iii) Dynamic Initialization.

 * (iv) Debugging of Exception Handling and Diagnostics.

 *

 * Revision 5.2  1995/10/20  14:11:15  wfs

 * gcc compilation changes.

 *

 * Revision 5.1  1995/09/15  13:13:36  wfs

 * Mike Gerrard's bug fix incorporated.

 *

 * Revision 5.0  1995/08/25  13:42:58  wfs

 * Preperation for August 25 Glue release

 *

 * Revision 3.4  1995/08/25  10:29:56  wfs

 * Register synonyms changed

 *

 * Revision 3.4  1995/08/25  10:29:56  wfs

 * Register synonyms changed

 *

 * Revision 3.1  95/04/10  16:28:04  16:28:04  wfs (William Simmonds)

 * Apr95 tape version.

 * 

 * Revision 3.0  95/03/30  11:18:54  11:18:54  wfs (William Simmonds)

 * Mar95 tape version with CRCR95_178 bug fix.

 * 

 * Revision 2.0  95/03/15  15:28:43  15:28:43  wfs (William Simmonds)

 * spec 3.1 changes implemented, tests outstanding.

 * 

 * Revision 1.1  95/01/11  13:16:12  13:16:12  wfs (William Simmonds)

 * Initial revision

 * 

*/

#define HPPATRANS_CODE

/* regexps.c

For trivial 'peephole' optimisations

*/

#include "config.h"

#include "expmacs.h"

#include "addrtypes.h"

#include "tags.h"

#include "move.h"

#include "bitsmacs.h"

#include "maxminmacs.h"

#include "shapemacs.h"

#include "common_types.h"

#include "regmacs.h"

#include "myassert.h"

#include "comment.h"

#include "check.h"

#include "regexps.h"

/* 22.11.94. Corrected bug found by Ian Currie, i.e. isglob(s) assertion

   added to line 351 */

int line;

regpeep regexps[64];		/* [0:31] fix pt - [32:47] floating pt */

bool sim_exp PROTO_S ( ( exp, exp ) ) ;

/* Same size and alignment and "both float or both fixed". */

bool eq_sze 

    PROTO_N ( ( as, bs ) )

    PROTO_T ( shape as X shape bs )

{

  if (is_floating(name(as)))

    return (name(as) == name(bs));

  if (is_floating(name(bs)))

    return 0;

  return (shape_size(as) == shape_size(bs) && shape_align(as) == shape_align(bs));

}

bool sim_explist 

    PROTO_N ( ( al, bl ) )

    PROTO_T ( exp al X exp bl )

{

  if (al == nilexp && bl == nilexp)

    return (1);

  if (al == nilexp || bl == nilexp)

    return (0);

  if (!sim_exp(al, bl))

    return (0);

  if (last(al) && last(bl))

    return (1);

  if (last(al) || last(bl))

    return (0);

  return (sim_explist(bro(al), bro(bl)));

}

bool sim_exp 

    PROTO_N ( ( a, b ) )

    PROTO_T ( exp a X exp b )

 /*

  * basically eq_exp except equal shapes requirement  is weakened to equal

  * sizes and alignments

  */

{

   if (name(a) == name(b))

   {

      if (name(a) == name_tag)

      {

	 return (son(a) == son(b) && no(a) == no(b) &&

	      eq_sze(sh(a), sh(b)));

      }

      if (!is_a(name(a)) || !eq_sze(sh(a), sh(b)))

	 return (0);

      if(name(a)==float_tag)/* NEW bit */

      {

	return eq_exp(son(a),son(b));

      }

      return (no(a) == no(b) && sim_explist(son(a), son(b)));

  };

  return (0);

}

/* forget all register - exp associations */

void clear_all 

    PROTO_Z ()

{

  int i;

  for (i = 0; i < 48; i++)

  {

    regexps[i].keptexp = nilexp;

    setregalt(regexps[i].inans, 0);

  }

}

/* forget reg i - exp association */

void clear_reg 

    PROTO_N ( ( i ) )

    PROTO_T ( int i )

{

  i = ABS_OF(i);

  if (i >= 0 && i < 48)

  {

    regexps[i].keptexp = nilexp;

    setregalt(regexps[i].inans, 0);

  }

}

/* find if e has already been evaluated into a register */

ans iskept 

    PROTO_N ( ( e ) )

    PROTO_T ( exp e )

{

  int i;

  ans nilans;

  setregalt(nilans, 0);		/* init nilans */

#ifdef NO_KEPT_OPTS

  /* no reg tracking */

  return nilans;

#endif

  /* reg tracking of unions unsafe, as views of location can differ */

  /* +++ track on fields */

  /* +++ safe to allow structs but not unions */

  if (name(sh(e)) == cpdhd)

  {

    return nilans;

  }

  for (i = 0; i < 48; i++)

  {

    exp ke = regexps[i].keptexp;

    bool isc = regexps[i].iscont;

    if (ke != nilexp)

    {

      /* there is an accociation with reg i */

      if (

	  ((!isc && sim_exp(ke, e)) ||

	   (name(e) == cont_tag && isc && eq_sze(sh(ke), sh(e))

	    && sim_exp(ke, son(e)))

	   )

	)

      {

	ans aa ;

	aa = (regexps[i].inans);

#if 0

	FULLCOMMENT4("iskept found: reg=%d isc=%d name(e)=%d name(son(e))=%d", i, isc, name(e), name(son(e)));

	FULLCOMMENT3("	hd(e)=%d hd(son(e))=%d hd(ke)=%d", name(sh(e)), name(sh(son(e))), name(sh(ke)));

	FULLCOMMENT3("	sim_exp(ke, e)=%d sim_exp(ke, son(e))=%d eq_size(sh(ke), sh(e))=%d",

		sim_exp(ke, e), sim_exp(ke, son(e)), eq_size(sh(ke), sh(e)));

#endif

	switch (discrim ( aa ))

	{

	case notinreg:

	  {

	    if (!aa.val.instoreans.adval)

	    {

	      /*

	       * the expression is given indirectly - it may have also been

	       * loaded into a register

	       */

	      continue;

	    }

	  }

	  /* FALLTHROUGH */

	default:

	  return aa;

	}

      }

      else if (name(ke) == cont_tag && !isc)

      {

	ans aq;

	aq = regexps[i].inans;

	if (discrim ( aq ) == notinreg)

	{

	  instore is;

	  is = insalt(aq);

	  if (!is.adval && is.b.offset == 0 && IS_FIXREG(is.b.base)

	      && sim_exp(son(ke), e))

	  {

	    /* the contents of req expression is here as a reg-offset */

	    is.adval = 1;

	    setinsalt(aq, is);

	    return aq;

	  }

	}

      }

      else if (name(ke) == reff_tag && !isc)

      {

	ans aq;

	aq = regexps[i].inans;

	if (discrim ( aq ) == notinreg)

	{

	  instore is;

	  is = insalt(aq);

	  if (is.adval && is.b.offset == (no(ke) / 8)

	      && IS_FIXREG(is.b.base)

	      && sim_exp(son(ke), e))

	  {

	    /* a ref select of req expression is here as a reg-offset */

	    is.adval = 1;

	    is.b.offset = 0;

	    setinsalt(aq, is);

	    return aq;

	  }

	}

      }

    }

  }

  return nilans;

}

/* set up exp - address association */

void keepexp 

    PROTO_N ( ( e, loc ) )

    PROTO_T ( exp e X ans loc )

{

  int reg=0;

  switch (discrim ( loc ))

  {

  case insomereg:

  case insomefreg:

    {

      fail("keep ? reg");

    }

#if USE_BITAD

  case bitad:

    {

      return;

    }

#endif

  case inreg:

    {

      reg = regalt(loc);

      break;

    }

  case infreg:

    {

      reg = fregalt(loc).fr + 32;

      break;

    }

  case notinreg:

    {

      reg = insalt(loc).b.base;

      if (!IS_FIXREG(reg))

	return;

      break;

    }

  default:{}

  }

  assert(reg >= 0 && reg < 48);

  assert(reg != GR1);

  regexps[reg].keptexp = e;

  regexps[reg].inans = loc;

  regexps[reg].iscont = 0;

}

/* set up cont(e)-reg association */

void keepcont 

    PROTO_N ( ( e, regcode ) )

    PROTO_T ( exp e X int regcode )

{

  freg fr;

  int reg = ABS_OF(regcode);

  assert(reg >= 0 && reg < 48);

  assert(reg != GR1);

  if (reg > 31)

  {

    fr.dble = ((regcode < 0) ? 1 : 0);

    fr.fr = reg - 32;

    setfregalt(regexps[reg].inans, fr);

  }

  else

  {

    instore is;

    is.b.base = regcode;

    is.b.offset = 0;

    is.adval = 1;

    setinsalt(regexps[reg].inans, is);

  }

  regexps[reg].keptexp = e;

  regexps[reg].iscont = 1;

}

/* set up e-reg association */

void keepreg 

    PROTO_N ( ( e, regcode ) )

    PROTO_T ( exp e X int regcode )

{

  freg fr;

  int reg = ABS_OF(regcode);

  assert(reg >= 0 && reg < 48);

  assert(reg != GR1);

  if (reg > 31)

  {

    fr.dble = ((regcode < 0) ? 1 : 0);

    fr.fr = reg - 32;

    setfregalt(regexps[reg].inans, fr);

  }

  else

  {

    instore is;

    is.b.base = regcode;

    is.b.offset = 0;

    is.adval = 1;

    setinsalt(regexps[reg].inans, is);

  }

  regexps[reg].keptexp = e;

  regexps[reg].iscont = 0;

}

bool couldeffect PROTO_S ( ( exp, exp ) ) ;

/* could e be lhs */

bool couldbe 

    PROTO_N ( ( e, lhs ) )

    PROTO_T ( exp e X exp lhs )

{

  int ne = name(e);

  exp s = son(e);

  if (ne == name_tag)

  {

    if (lhs != 0 && s == son(lhs))

    {

      return 1;

    }

    if (isvar(s))

    {

      return (lhs == 0 && (isvis(s) || isglob(s)));

    }

    if (IS_A_PROC(s))

      return (lhs == 0);

    if (son(s) == nilexp)

      return 1;

    return couldbe(son(s), lhs);

  }

  if (ne == cont_tag)

  {

    if (lhs != 0 && name(s) == name_tag && son(s) != nilexp)

    {

      return (son(s) == son(lhs) || isvis(son(lhs)) || isvis(son(s)));

    }

    return 1;

  }

  if (ne == reff_tag || ne == field_tag)

  {

    return couldbe(s, lhs);

  }

  if (ne == addptr_tag || ne == subptr_tag)

  {

    return (couldbe(s, lhs) || couldeffect(bro(s), lhs));

  }

  return 1;

}

/* could alteration to z effect e? */

bool couldeffect 

    PROTO_N ( ( e, z /* a name or zero */ ) )

    PROTO_T ( exp e X exp z /* a name or zero */ )

{

  int ne = name(e);

  if (ne == cont_tag)

  {

    return couldbe(son(e), z);

  }

  if (ne == name_tag)

  {

    if (isvar(son(e)))

      return (z == 0 && isvis(son(e)));

    if ( IS_A_PROC(son(e)) )

      return 0;

    if (son(son(e)) == nilexp)

      return 1 /* could it happen? */ ;

    return couldeffect(son(son(e)), z);

  }

  if (ne < plus_tag || ne == contvol_tag)

    return 1;

  e = son(e);

  while (e != nilexp)

  {

    if (couldeffect(e, z))

      return 1;

    if (last(e))

      return 0;

    e = bro(e);

  }

  return 0;

}

bool dependson 

    PROTO_N ( ( e, isc, z ) )

    PROTO_T ( exp e X bool isc X exp z )

{				/* does e depend on z */

  if (e == nilexp)

  {

    return 0;

  }

  for (;;)

  {

    if (name(z) == reff_tag || name(z) == addptr_tag ||

	name(z) == subptr_tag)

    {

      z = son(z);

    }

    if (name(z) != name_tag)

    {

      if (name(z) != cont_tag)

	return 1;

      z = 0;

      break;

    }

    if (isvar(son(z)))

      break;

    if ( IS_A_PROC(son(z)) )

    {

      z = 0;

      break;

    }

    if (son(son(z)) == nilexp)

      return 1;			/* can it happen? */

    z = son(son(z));

  }

  /* z is now unambiguous variable name or 0 meaning some contents */

  return ((isc) ? couldbe(e, z) : couldeffect(e, z));

}

/* remove association of any register which depends on lhs */

void clear_dep_reg 

    PROTO_N ( ( lhs ) )

    PROTO_T ( exp lhs )

{

  int i;

  for (i = 0; i < 48; i++)

  {

    if (dependson(regexps[i].keptexp, regexps[i].iscont, lhs))

    {

      regexps[i].keptexp = nilexp;

      setregalt(regexps[i].inans, 0);

    }

  }

}