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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: tempdecs.c,v $

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

 * First version to be checked into rolling release.

 *

 * Revision 1.2  1995/12/18  13:12:40  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  14:14:22  wfs

 * #included "muldvrem.h" for gcc compilation.

 *

 * Revision 5.1  1995/09/07  15:44:58  wfs

 * Fixed bug in "APPLYLIKE".

 *

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

 * Preperation for August 25 Glue release

 *

 * Revision 3.4  1995/08/25  10:34:20  wfs

 * Refinement of "APPLYLIKE" required for 3.1 and 4.0 compatability

 *

 * Revision 3.4  1995/08/25  10:34:20  wfs

 * Refinement of "APPLYLIKE" required for 3.1 and 4.0 compatability

 *

 * Revision 3.1  95/04/10  16:28:30  16:28:30  wfs (William Simmonds)

 * Apr95 tape version.

 * 

 * Revision 3.0  95/03/30  11:19:06  11:19:06  wfs (William Simmonds)

 * Mar95 tape version with CRCR95_178 bug fix.

 * 

 * Revision 2.0  95/03/15  15:28:59  15:28:59  wfs (William Simmonds)

 * spec 3.1 changes implemented, tests outstanding.

 * 

 * Revision 1.1  95/01/11  13:19:10  13:19:10  wfs (William Simmonds)

 * Initial revision

 * 

*/

#define HPPATRANS_CODE

/* tempdec.c - is the value in the declaration required over proc calls ?

    if it isn't, declaration can be allocated in t-reg, rather than

    s-reg.

*/

#include "config.h"

#include "tags.h"

#include "common_types.h"

#include "exp.h"

#include "const.h"

#include "expmacs.h"

#include "bitsmacs.h"

#include "muldvrem.h"

#include "tempdecs.h"

/*

    IS THE EXPRESSION e A PROCEDURE APPLICATION?

*/

#define APPLYLIKE( e ) ( name(e)==apply_tag || name(e)==apply_general_tag ||\

			 name(e)==tail_call_tag || is_muldivrem_call(e) )

/*

    FLAG : APPLY TEMPDEF OPTIMISATION?

*/

bool tempdecopt ;     /* flag to allow this optimisation, set in main () */

/*

    VARIABLES SET BY TRACE_USES

*/

static int nouses ;

static bool useinpar ;

/*

    Reduces nouses for each non-assignment use of id encountered in e,

    sets useinpar if use in actual parameter (or function) position,

    terminates with 0 on applications or jumps, terminates with 2 on

    assignment to id, otherwise delivers 1.

*/

int trace_uses 

    PROTO_N ( ( e, id ) )

    PROTO_T ( exp e X exp id )

{

    if ( APPLYLIKE ( e ) ) {

	int u = nouses ;

	int p = 1 ;

	exp l = son ( e ) ;

	while ( p == 1 ) {

	    p = trace_uses ( l, id ) ;

	    if ( u != nouses || p == 2 ) useinpar = 1 ;

	    if ( p == 0 ) nouses = u ;

	    if ( last ( l ) ) break ;

	    l = bro ( l ) ;

	}

	return ( 0 ) ;

    }

    switch ( name ( e ) ) {

	case env_offset_tag:

	case name_tag : {

	    nouses -= ( son ( e ) == id ? 1 : 0 ) ;

	    return ( 1 ) ;

	}

	case ident_tag : {

	    exp f = son ( e ) ;

	    exp s = bro ( f ) ;

	    int a ;

	    if ( ( props ( e ) & defer_bit ) != 0 ) {

		exp t = f ;

		f = s ;

		s = t ;

	    }

	    a = trace_uses ( f, id ) ;

	    if ( a != 1 ) return ( a ) ;

	    return ( trace_uses ( s, id ) ) ;

	}

	case case_tag : {

	    trace_uses ( son ( e ), id ) ;

	    return ( 0 ) ;

	}

	case labst_tag : {

	    return ( 0 ) ;

	}

	case seq_tag : {

	    exp s = son ( son ( e ) ) ;

	    for ( ; ; ) {

		int el = trace_uses ( s, id ) ;

		if ( el != 1 ) return ( el ) ;

		if ( last ( s ) ) {

		    return ( trace_uses ( bro ( son ( e ) ), id ) ) ;

		}

		s = bro ( s ) ;

	    }

	    /* NOT REACHED */

	    break ;

	}

	case test_tag: case goto_lv_tag:{

		int nu = nouses;

		if (trace_uses(son(e),id) != 1 || 

				trace_uses(bro(son(e)), id) !=1 ){

			nouses = nu;

		}

		return 0;

	}

	case ass_tag : {

	    if ( isvar ( id ) && name ( son ( e ) ) == name_tag &&

		 son ( son ( e ) ) == id ) {

		trace_uses ( bro ( son ( e ) ), id ) ;

		return ( 2 ) ;

	    } else if ( APPLYLIKE ( bro ( son ( e ) ) ) ) {

		return ( trace_uses ( bro ( son ( e ) ), id ) ) ;

	    }

	    /* Fall through */

	}

	default : {

	    exp s = son ( e ) ;

	    int nu = nouses ;	 /* s list can be done in any order ... */

	    if ( s == nilexp ) return ( 1 ) ;

	    for ( ; ; ) {

		int el = trace_uses ( s, id ) ;

		if ( el != 1 ) {

		    /* ... so reset nouses if any terminate */

		    nouses = nu ;

		    return el ;

		}

		if ( last ( s ) ) return ( 1 ) ;

		s = bro ( s ) ;

	    }

	    /* NOT REACHED */

	    break ;

	}

    }

    /* NOT REACHED */

    return ( 0 ) ;

}

/*

    APPLY TRACE_USES TO DYNAMIC SUCCESSORS OF a

*/

void after_a 

    PROTO_N ( ( a, id ) )

    PROTO_T ( exp a X exp id )

{

    char n ;

    exp dad ;

    exp l ;

    tailrec : {

	dad = father ( a ) ;

	n = name ( dad ) ;

	if ( nouses == 0 ) return ;

	if ( n == cond_tag || n == rep_tag || n == solve_tag ||

	     n == labst_tag || n == case_tag || n == goto_tag ||

	     n == test_tag || n == goto_lv_tag || APPLYLIKE ( dad ) ) {

	    /* Don't try too hard! */

	    while ( APPLYLIKE ( dad ) && dad != id ) dad = father ( dad ) ;

	    if ( APPLYLIKE ( dad ) ) {

		useinpar = 1 ;

	    }

	    return ;

	}

	for ( l = a ; !last ( l ) ; l = bro ( l ) )

	{

	    int u = trace_uses ( bro ( l ), id ) ;

	    if ( u != 1 || nouses == 0 ) return ;

	}

	a = dad ;

    }

    if ( dad != id ) goto tailrec ;

    return ;

}

bool simple_seq 

    PROTO_N ( ( e, id ) )

    PROTO_T ( exp e X exp id )

{

    exp dad = father ( e ) ;

    for ( ; ; ) {

	if ( dad == id ) return ( 1 ) ;

	if ( name ( dad ) == seq_tag || name ( dad ) == 0 ||

	     name ( dad ) == ident_tag ) {

	    dad = father ( dad ) ;

	} else {

	    return ( 0 ) ;

	}

    }

    /* NOT REACHED */

}

bool tempdec 

    PROTO_N ( ( e, enoughs ) )

    PROTO_T ( exp e X bool enoughs )

{

    /*

 * e is a local declaration ; 'enoughs' is a misnomer to say whether there

 * are t-regs available delivers 1 if e can be allocated into t-reg or par

 * reg

 */

    exp p ;

    if ( !tempdecopt ) return ( 0 ) ;

    nouses = 0 ;

    useinpar = 0 ;

    if ( isvar ( e ) ) {

	for ( p = pt ( e ) ; p != nilexp ; p = pt ( p ) ) {

	    /* find no of uses which are not assignments to id ... */

	    if ( !last ( p ) && last ( bro ( p ) ) &&

		 name ( bro ( bro ( p ) ) ) == ass_tag ) {

		if ( !simple_seq ( bro ( bro ( p ) ), e ) ) return  ( 0 ) ;

		/* ... in simple sequence */

		continue ;

	    }

	    nouses++ ;

	}

    } else {

	nouses = no ( e ) ;

    }

    /*

 * trace simple successors to assignmnts or init to id to find if all uses

 * occur before unpredictable change of control ( or another assignment to

 * id )

 */

    if ( name ( son ( e ) ) != clear_tag || isparam ( e ) ) {

	after_a ( son ( e ), e ) ;

    }

    if ( isvar ( e ) ) {

	for ( p = pt ( e ) ; p != nilexp ; p = pt ( p ) ) {

	    if ( !last ( p ) && last ( bro ( p ) ) &&

		 name ( bro ( bro ( p ) ) ) == ass_tag ) {

		after_a ( bro ( bro ( p ) ), e ) ;

	    }

	}

    }

    if ( nouses == 0 && ( enoughs || !useinpar ) ) {

#if 0

	/* +++ temp circumvention, we need to calculate t-reg reqt better when

     some not allowed by props ( e ) |= notparreg */

	if ( useinpar ) return ( 0 ) ;

#else

	if ( useinpar ) props ( e ) |= notparreg ;     /* don't allocate this into par reg */

#endif

	return ( 1 ) ;

    }

    return ( 0 ) ;

}