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/***** tl_spin: tl_rewrt.c *****/
/* Copyright (c) 1995-2003 by Lucent Technologies, Bell Laboratories. */
/* All Rights Reserved. This software is for educational purposes only. */
/* No guarantee whatsoever is expressed or implied by the distribution of */
/* this code. Permission is given to distribute this code provided that */
/* this introductory message is not removed and no monies are exchanged. */
/* Software written by Gerard J. Holzmann. For tool documentation see: */
/* http://spinroot.com/ */
/* Send all bug-reports and/or questions to: bugs@spinroot.com */
/* Based on the translation algorithm by Gerth, Peled, Vardi, and Wolper, */
/* presented at the PSTV Conference, held in 1995, Warsaw, Poland 1995. */
#include "tl.h"
extern int tl_verbose;
static Node *can = ZN;
void
ini_rewrt(void)
{
can = ZN;
}
Node *
right_linked(Node *n)
{
if (!n) return n;
if (n->ntyp == AND || n->ntyp == OR)
while (n->lft && n->lft->ntyp == n->ntyp)
{ Node *tmp = n->lft;
n->lft = tmp->rgt;
tmp->rgt = n;
n = tmp;
}
n->lft = right_linked(n->lft);
n->rgt = right_linked(n->rgt);
return n;
}
Node *
canonical(Node *n)
{ Node *m; /* assumes input is right_linked */
if (!n) return n;
if ((m = in_cache(n)) != ZN)
return m;
n->rgt = canonical(n->rgt);
n->lft = canonical(n->lft);
return cached(n);
}
Node *
push_negation(Node *n)
{ Node *m;
Assert(n->ntyp == NOT, n->ntyp);
switch (n->lft->ntyp) {
case TRUE:
Debug("!true => false\n");
releasenode(0, n->lft);
n->lft = ZN;
n->ntyp = FALSE;
break;
case FALSE:
Debug("!false => true\n");
releasenode(0, n->lft);
n->lft = ZN;
n->ntyp = TRUE;
break;
case NOT:
Debug("!!p => p\n");
m = n->lft->lft;
releasenode(0, n->lft);
n->lft = ZN;
releasenode(0, n);
n = m;
break;
case V_OPER:
Debug("!(p V q) => (!p U !q)\n");
n->ntyp = U_OPER;
goto same;
case U_OPER:
Debug("!(p U q) => (!p V !q)\n");
n->ntyp = V_OPER;
goto same;
#ifdef NXT
case NEXT:
Debug("!X -> X!\n");
n->ntyp = NEXT;
n->lft->ntyp = NOT;
n->lft = push_negation(n->lft);
break;
#endif
case AND:
Debug("!(p && q) => !p || !q\n");
n->ntyp = OR;
goto same;
case OR:
Debug("!(p || q) => !p && !q\n");
n->ntyp = AND;
same: m = n->lft->rgt;
n->lft->rgt = ZN;
n->rgt = Not(m);
n->lft->ntyp = NOT;
m = n->lft;
n->lft = push_negation(m);
break;
}
return rewrite(n);
}
static void
addcan(int tok, Node *n)
{ Node *m, *prev = ZN;
Node **ptr;
Node *N;
Symbol *s, *t; int cmp;
if (!n) return;
if (n->ntyp == tok)
{ addcan(tok, n->rgt);
addcan(tok, n->lft);
return;
}
N = dupnode(n);
if (!can)
{ can = N;
return;
}
s = DoDump(N);
if (can->ntyp != tok) /* only one element in list so far */
{ ptr = &can;
goto insert;
}
/* there are at least 2 elements in list */
prev = ZN;
for (m = can; m->ntyp == tok && m->rgt; prev = m, m = m->rgt)
{ t = DoDump(m->lft);
if (t != ZS)
cmp = strcmp(s->name, t->name);
else
cmp = 0;
if (cmp == 0) /* duplicate */
return;
if (cmp < 0)
{ if (!prev)
{ can = tl_nn(tok, N, can);
return;
} else
{ ptr = &(prev->rgt);
goto insert;
} } }
/* new entry goes at the end of the list */
ptr = &(prev->rgt);
insert:
t = DoDump(*ptr);
cmp = strcmp(s->name, t->name);
if (cmp == 0) /* duplicate */
return;
if (cmp < 0)
*ptr = tl_nn(tok, N, *ptr);
else
*ptr = tl_nn(tok, *ptr, N);
}
static void
marknode(int tok, Node *m)
{
if (m->ntyp != tok)
{ releasenode(0, m->rgt);
m->rgt = ZN;
}
m->ntyp = -1;
}
Node *
Canonical(Node *n)
{ Node *m, *p, *k1, *k2, *prev, *dflt = ZN;
int tok;
if (!n) return n;
tok = n->ntyp;
if (tok != AND && tok != OR)
return n;
can = ZN;
addcan(tok, n);
#if 0
Debug("\nA0: "); Dump(can);
Debug("\nA1: "); Dump(n); Debug("\n");
#endif
releasenode(1, n);
/* mark redundant nodes */
if (tok == AND)
{ for (m = can; m; m = (m->ntyp == AND) ? m->rgt : ZN)
{ k1 = (m->ntyp == AND) ? m->lft : m;
if (k1->ntyp == TRUE)
{ marknode(AND, m);
dflt = True;
continue;
}
if (k1->ntyp == FALSE)
{ releasenode(1, can);
can = False;
goto out;
} }
for (m = can; m; m = (m->ntyp == AND) ? m->rgt : ZN)
for (p = can; p; p = (p->ntyp == AND) ? p->rgt : ZN)
{ if (p == m
|| p->ntyp == -1
|| m->ntyp == -1)
continue;
k1 = (m->ntyp == AND) ? m->lft : m;
k2 = (p->ntyp == AND) ? p->lft : p;
if (isequal(k1, k2))
{ marknode(AND, p);
continue;
}
if (anywhere(OR, k1, k2))
{ marknode(AND, p);
continue;
}
} }
if (tok == OR)
{ for (m = can; m; m = (m->ntyp == OR) ? m->rgt : ZN)
{ k1 = (m->ntyp == OR) ? m->lft : m;
if (k1->ntyp == FALSE)
{ marknode(OR, m);
dflt = False;
continue;
}
if (k1->ntyp == TRUE)
{ releasenode(1, can);
can = True;
goto out;
} }
for (m = can; m; m = (m->ntyp == OR) ? m->rgt : ZN)
for (p = can; p; p = (p->ntyp == OR) ? p->rgt : ZN)
{ if (p == m
|| p->ntyp == -1
|| m->ntyp == -1)
continue;
k1 = (m->ntyp == OR) ? m->lft : m;
k2 = (p->ntyp == OR) ? p->lft : p;
if (isequal(k1, k2))
{ marknode(OR, p);
continue;
}
if (anywhere(AND, k1, k2))
{ marknode(OR, p);
continue;
}
} }
for (m = can, prev = ZN; m; ) /* remove marked nodes */
{ if (m->ntyp == -1)
{ k2 = m->rgt;
releasenode(0, m);
if (!prev)
{ m = can = can->rgt;
} else
{ m = prev->rgt = k2;
/* if deleted the last node in a chain */
if (!prev->rgt && prev->lft
&& (prev->ntyp == AND || prev->ntyp == OR))
{ k1 = prev->lft;
prev->ntyp = prev->lft->ntyp;
prev->sym = prev->lft->sym;
prev->rgt = prev->lft->rgt;
prev->lft = prev->lft->lft;
releasenode(0, k1);
}
}
continue;
}
prev = m;
m = m->rgt;
}
out:
#if 0
Debug("A2: "); Dump(can); Debug("\n");
#endif
if (!can)
{ if (!dflt)
fatal("cannot happen, Canonical", (char *) 0);
return dflt;
}
return can;
}