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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: tempdecs.c,v 1.1.1.1 1998/01/17 15:56:01 release Exp $ */
#ifndef lint
static char vcid[] = "$Id: tempdecs.c,v 1.1.1.1 1998/01/17 15:56:01 release Exp $";
#endif /* lint */
/*
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 "tempdecs.h"
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 posn
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 )
{
Assert(e!=(exp)0);
Assert(id!=(exp)0);
switch(name(e)) {
case name_tag: {
nouses -=(son(e)==id);
return (1);
}
case apply_general_tag :
case apply_tag :{
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;
}
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);
}
}
case ass_tag: {
if (isvar(id) && name(son(e))==name_tag && son(son(e))==id) {
trace_uses(bro(son(e)),id);
return 2;
}
else{
int nu = nouses;
if (trace_uses(son(e),id) != 1 ||
trace_uses(bro(son(e)), id) !=1 ){
nouses = nu;
return 0;
}
return 1;
}
}
case goto_lv_tag:
{
int nu = nouses;
if(trace_uses(son(e),id) != 1){
nouses = nu;
}
return 0;
}
case test_tag:{
int nu = nouses;
if((trace_uses(son(e),id) != 1) || (trace_uses(bro(son(e)),id)!= 1)){
nouses = nu;
}
return 0;
}
case solve_tag:case cond_tag: {
return trace_uses(son(e),id);
}
case goto_tag:case rep_tag:
return 0;
case current_env_tag:
return 0;
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);
}
}
}
}
void after_a
PROTO_N ( ( a, id ) )
PROTO_T ( exp a X exp id )
{
/* apply trace_uses to dynamic successors of a */
exp dad ;
exp l;
tailrec: dad = father(a);
if (nouses == 0) return;
if (name(dad)==cond_tag || name(dad)==rep_tag || name(dad) == res_tag
|| name(dad) == solve_tag || name(dad) == labst_tag
|| name(dad) == case_tag || name(dad)== goto_lv_tag
|| name(dad) == test_tag || name(dad) == apply_tag) {
/* dont try too hard ! */
while (name(dad) != apply_tag && dad !=id) dad = father(dad);
if (name(dad) == apply_tag) { 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;
}
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;
}
}
bool tempdecopt = 0; /* flag to allow this optimisation; -Tt
sets to 0 */
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 (useinpar) props(e) |= notparreg;
/* don't allocate this into par reg */
return 1;
}
return 0;
}