#include "c.h"

static char rcsid[] = "$Id: stmt.nw,v 2.7 1997/05/05 18:19:39 drh Exp drh $";

#define SWSIZE 512

#define den(i,j) ((j-buckets[i]+1.0)/(v[j]-v[buckets[i]]+1))

struct code codehead = { Start };
Code codelist = &codehead;
float density = 0.5;
Table stmtlabs;

static int foldcond(Tree e1, Tree e2);
static void caselabel(Swtch, long, int);
static void cmp(int, Symbol, long, int);
static Tree conditional(int);
static void dostmt(int, Swtch, int);
static int equal(Symbol, Symbol);
static void forstmt(int, Swtch, int);
static void ifstmt(int, int, Swtch, int);
static Symbol localaddr(Tree);
static void stmtlabel(void);
static void swstmt(int, int, int);
static void whilestmt(int, Swtch, int);
Code code(int kind) {
        Code cp;

        if (!reachable(kind))
	         warning("unreachable code\n");

        NEW(cp, FUNC);
        cp->kind = kind;
        cp->prev = codelist;
        cp->next = NULL;
        codelist->next = cp;
        codelist = cp;
        return cp;
}
int reachable(int kind) {
        Code cp;

        if (kind > Start) {
                Code cp;
                for (cp = codelist; cp->kind < Label; )
                        cp = cp->prev;
                if (cp->kind == Jump || cp->kind == Switch)
                        return 0;
        }
        return 1;
}
void addlocal(Symbol p) {
        if (!p->defined) {
                code(Local)->u.var = p;
                p->defined = 1;
                p->scope = level;
        }
}
void definept(Coordinate *p) {
        Code cp = code(Defpoint);

        cp->u.point.src = p ? *p : src;
        cp->u.point.point = npoints;
        if (ncalled > 0) {
	        int n = findcount(cp->u.point.src.file,
	                cp->u.point.src.x, cp->u.point.src.y);
	        if (n > 0)
	                refinc = (float)n/ncalled;
	}
        if (glevel > 2) locus(identifiers, &cp->u.point.src);
        if (events.points)
                {
		        Tree e = NULL;
		        apply(events.points, &cp->u.point.src, &e);
		        if (e)
		                listnodes(e, 0, 0);
		}
}
void statement(int loop, Swtch swp, int lev) {
        float ref = refinc;

        if (Aflag >= 2 && lev == 15)
                warning("more than 15 levels of nested statements\n");
        switch (t) {
        case IF:       ifstmt(genlabel(2), loop, swp, lev + 1);
 break;
        case WHILE:    whilestmt(genlabel(3), swp, lev + 1); break;
        case DO:       dostmt(genlabel(3), swp, lev + 1); expect(';');
					break;

        case FOR:      forstmt(genlabel(4), swp, lev + 1);
 break;
        case BREAK:    walk(NULL, 0, 0);
		       definept(NULL);
		       if (swp && swp->lab > loop)
		               branch(swp->lab + 1);
		       else if (loop)
		               branch(loop + 2);
		       else
		               error("illegal break statement\n");
		       t = gettok(); expect(';');
					   break;

        case CONTINUE: walk(NULL, 0, 0);
		       definept(NULL);
		       if (loop)
		               branch(loop + 1);
		       else
		               error("illegal continue statement\n");
		       t = gettok(); expect(';');
					      break;

        case SWITCH:   swstmt(loop, genlabel(2), lev + 1);
 break;
        case CASE:     {
		               int lab = genlabel(1);
		               if (swp == NULL)
		                       error("illegal case label\n");
		               definelab(lab);
		               while (t == CASE) {
		                       static char stop[] = { IF, ID, 0 };
		                       Tree p;
		                       t = gettok();
		                       p = constexpr(0);
		                       if (generic(p->op) == CNST && isint(p->type)) {
		                               if (swp) {
		                                       needconst++;
		                                       p = cast(p, swp->sym->type);
		                                       if (p->type->op == UNSIGNED)
		                                               p->u.v.i = extend(p->u.v.u, p->type);
		                                       needconst--;
		                                       caselabel(swp, p->u.v.i, lab);
		                               }
		                       } else
		                               error("case label must be a constant integer expression\n");

		                       test(':', stop);
		               }
		               statement(loop, swp, lev);
		       } break;
        case DEFAULT:  if (swp == NULL)
		               error("illegal default label\n");
		       else if (swp->deflab)
		               error("extra default label\n");
		       else {
		               swp->deflab = findlabel(swp->lab);
		               definelab(swp->deflab->u.l.label);
		       }
		       t = gettok();
		       expect(':');
		       statement(loop, swp, lev); break;
        case RETURN:   {
		               Type rty = freturn(cfunc->type);
		               t = gettok();
		               definept(NULL);
		               if (t != ';')
		                       if (rty == voidtype) {
		                               error("extraneous return value\n");
		                               expr(0);
		                               retcode(NULL);
		                       } else
		                               retcode(expr(0));
		               else {
		                       if (rty != voidtype)
		                               warning("missing return value\n");
		                       retcode(NULL);
		               }
		               branch(cfunc->u.f.label);
		       } expect(';');
					    break;

        case '{':      compound(loop, swp, lev + 1); break;
        case ';':      definept(NULL); t = gettok(); break;
        case GOTO:     walk(NULL, 0, 0);
		       definept(NULL);
		       t = gettok();
		       if (t == ID) {
		               Symbol p = lookup(token, stmtlabs);
		               if (p == NULL) {
			               p = install(token, &stmtlabs, 0, FUNC);
			               p->scope = LABELS;
			               p->u.l.label = genlabel(1);
			               p->src = src;
			       }
		               use(p, src);
		               branch(p->u.l.label);
		               t = gettok();
		       } else
		               error("missing label in goto\n"); expect(';');
					  break;

        case ID:       if (getchr() == ':') {
		               stmtlabel();
		               statement(loop, swp, lev);
		               break;
		       }
        default:       definept(NULL);
		       if (kind[t] != ID) {
		               error("unrecognized statement\n");
		               t = gettok();
		       } else {
		               Tree e = expr0(0);
		               listnodes(e, 0, 0);
		               if (nodecount == 0 || nodecount > 200)
		                       walk(NULL, 0, 0);
		               else if (glevel) walk(NULL, 0, 0);
		               deallocate(STMT);
		       } expect(';');
						break;

        }
        if (kind[t] != IF && kind[t] != ID
	&& t != '}' && t != EOI) {
	        static char stop[] = { IF, ID, '}', 0 };
	        error("illegal statement termination\n");
	        skipto(0, stop);
	}
        refinc = ref;
}

static void ifstmt(int lab, int loop, Swtch swp, int lev) {
        t = gettok();
        expect('(');
        definept(NULL);
        walk(conditional(')'), 0, lab);
        refinc /= 2.0;
        statement(loop, swp, lev);
        if (t == ELSE) {
                branch(lab + 1);
                t = gettok();
                definelab(lab);
                statement(loop, swp, lev);
                if (findlabel(lab + 1)->ref)
                        definelab(lab + 1);
        } else
                definelab(lab);
}
static Tree conditional(int tok) {
        Tree p = expr(tok);

        if (Aflag > 1 && isfunc(p->type))
                warning("%s used in a conditional expression\n",
                        funcname(p));
        return cond(p);
}
static void stmtlabel(void) {
        Symbol p = lookup(token, stmtlabs);

        if (p == NULL) {
	        p = install(token, &stmtlabs, 0, FUNC);
	        p->scope = LABELS;
	        p->u.l.label = genlabel(1);
	        p->src = src;
	}
        if (p->defined)
                error("redefinition of label `%s' previously defined at %w\n", p->name, &p->src);

        p->defined = 1;
        definelab(p->u.l.label);
        t = gettok();
        expect(':');
}
static void forstmt(int lab, Swtch swp, int lev) {
        int once = 0;
        Tree e1 = NULL, e2 = NULL, e3 = NULL;
        Coordinate pt2, pt3;
        
        t = gettok();
        expect('(');
        definept(NULL);
        if (kind[t] == ID)
	        e1 = texpr(expr0, ';', FUNC);
	else
	        expect(';');
	walk(e1, 0, 0);
	pt2 = src;
	refinc *= 10.0;
	if (kind[t] == ID)
	        e2 = texpr(conditional, ';', FUNC);
	else
	        expect(';');
	pt3 = src;
	if (kind[t] == ID)
	        e3 = texpr(expr0, ')', FUNC);
	else {
	        static char stop[] = { IF, ID, '}', 0 };
	        test(')', stop);
	}
	if (e2) {
	        once = foldcond(e1, e2);
	        if (!once)
	                branch(lab + 3);
	}
	definelab(lab);
	statement(lab, swp, lev);
	definelab(lab + 1);
	definept(&pt3);
	if (e3)
	        walk(e3, 0, 0);
	if (e2) {
	        if (!once)
	                definelab(lab + 3);
	        definept(&pt2);
	        walk(e2, lab, 0);
	} else {
	        definept(&pt2);
	        branch(lab);
	}
	if (findlabel(lab + 2)->ref)
	        definelab(lab + 2);
}
static void swstmt(int loop, int lab, int lev) {
        Tree e;
        struct swtch sw;
        Code head, tail;

        t = gettok();
        expect('(');
        definept(NULL);
        e = expr(')');
        if (!isint(e->type)) {
	        error("illegal type `%t' in switch expression\n",
	                e->type);
	        e = retype(e, inttype);
	}
	e = cast(e, promote(e->type));
        if (generic(e->op) == INDIR && isaddrop(e->kids[0]->op)
	&& e->kids[0]->u.sym->type == e->type
	&& !isvolatile(e->kids[0]->u.sym->type)) {
	        sw.sym = e->kids[0]->u.sym;
	        walk(NULL, 0, 0);
	} else {
	        sw.sym = genident(REGISTER, e->type, level);
	        addlocal(sw.sym);
	        walk(asgn(sw.sym, e), 0, 0);
	}
        head = code(Switch);
        sw.lab = lab;
        sw.deflab = NULL;
        sw.ncases = 0;
        sw.size = SWSIZE;
        sw.values = newarray(SWSIZE, sizeof *sw.values, FUNC);
        sw.labels = newarray(SWSIZE, sizeof *sw.labels, FUNC);
        refinc /= 10.0;
        statement(loop, &sw, lev);
        if (sw.deflab == NULL) {
	        sw.deflab = findlabel(lab);
	        definelab(lab);
	        if (sw.ncases == 0)
	                warning("switch statement with no cases\n");
	}
	if (findlabel(lab + 1)->ref)
	        definelab(lab + 1);
        tail = codelist;
	codelist = head->prev;
	codelist->next = head->prev = NULL;
	if (sw.ncases > 0)
	        swgen(&sw);
	branch(lab);
	head->next->prev = codelist;
	codelist->next = head->next;
	codelist = tail;
}
static void caselabel(Swtch swp, long val, int lab) {
        int k;

        if (swp->ncases >= swp->size)
                {
		long   *vals = swp->values;
		Symbol *labs = swp->labels;
		swp->size *= 2;
		swp->values = newarray(swp->size, sizeof *swp->values, FUNC);
		swp->labels = newarray(swp->size, sizeof *swp->labels, FUNC);
		for (k = 0; k < swp->ncases; k++) {
		        swp->values[k] = vals[k];
		        swp->labels[k] = labs[k];
		}
		}
        k = swp->ncases;
        for ( ; k > 0 && swp->values[k-1] >= val; k--) {
                swp->values[k] = swp->values[k-1];
                swp->labels[k] = swp->labels[k-1];
        }
        if (k < swp->ncases && swp->values[k] == val)
                error("duplicate case label `%d'\n", val);
        swp->values[k] = val;
        swp->labels[k] = findlabel(lab);
        ++swp->ncases;
        if (Aflag >= 2 && swp->ncases == 258)
                warning("more than 257 cases in a switch\n");
}
void swgen(Swtch swp) {
        int *buckets, k, n;
        long *v = swp->values;

        buckets = newarray(swp->ncases + 1,
                sizeof *buckets, FUNC);
        for (n = k = 0; k < swp->ncases; k++, n++) {
                buckets[n] = k;
                while (n > 0 && den(n-1, k) >= density)
                        n--;
        }
        buckets[n] = swp->ncases;
        swcode(swp, buckets, 0, n - 1);
}
void swcode(Swtch swp, int b[], int lb, int ub) {
        int hilab, lolab, l, u, k = (lb + ub)/2;
        long *v = swp->values;

        if (k > lb && k < ub) {
	        lolab = genlabel(1);
	        hilab = genlabel(1);
	} else if (k > lb) {
	        lolab = genlabel(1);
	        hilab = swp->deflab->u.l.label;
	} else if (k < ub) {
	        lolab = swp->deflab->u.l.label;
	        hilab = genlabel(1);
	} else
	        lolab = hilab = swp->deflab->u.l.label;
	l = b[k];
	u = b[k+1] - 1;
	if (u - l + 1 <= 3)
	        {
		        int i;
		        for (i = l; i <= u; i++)
		                cmp(EQ, swp->sym, v[i], swp->labels[i]->u.l.label);
		        if (k > lb && k < ub)
		                cmp(GT, swp->sym, v[u], hilab);
		        else if (k > lb)
		                cmp(GT, swp->sym, v[u], hilab);
		        else if (k < ub)
		                cmp(LT, swp->sym, v[l], lolab);
		        else
		                assert(lolab == hilab),
		                branch(lolab);
		        walk(NULL, 0, 0);
		}
	else {
	        Type ty = signedint(swp->sym->type);
		Symbol table = genident(STATIC,
		        array(voidptype, u - l + 1, 0), LABELS);
		(*IR->defsymbol)(table);
		cmp(LT, swp->sym, v[l], lolab);
		cmp(GT, swp->sym, v[u], hilab);
		walk(tree(JUMP, voidtype,
		        rvalue((*optree['+'])(ADD, pointer(idtree(table)),
		                (*optree['-'])(SUB,
		                        cast(idtree(swp->sym), ty),
		                        cnsttree(ty, v[l])))), NULL), 0, 0);
		code(Switch);
		codelist->u.swtch.table = table;
		codelist->u.swtch.sym = swp->sym;
		codelist->u.swtch.deflab = swp->deflab;
		codelist->u.swtch.size = u - l + 1;
		codelist->u.swtch.values = &v[l];
		codelist->u.swtch.labels = &swp->labels[l];
		if (v[u] - v[l] + 1 >= 10000)
		        warning("switch generates a huge table\n");
	}
	if (k > lb) {
	        assert(lolab != swp->deflab->u.l.label);
	        definelab(lolab);
	        swcode(swp, b, lb, k - 1);
	}
	if (k < ub) {
	        assert(hilab != swp->deflab->u.l.label);
	        definelab(hilab);
	        swcode(swp, b, k + 1, ub);
	}
}
static void cmp(int op, Symbol p, long n, int lab) {
        listnodes(eqtree(op,
                        idtree(p),
                        cast(cnsttree(longtype, n), p->type)),
                lab, 0);
}
void retcode(Tree p) {
        Type ty;

        if (p == NULL) {
                if (events.returns)
                        apply(events.returns, cfunc, NULL);
                return;
        }
        p = pointer(p);
	ty = assign(freturn(cfunc->type), p);
	if (ty == NULL) {
	        error("illegal return type; found `%t' expected `%t'\n",
	                p->type, freturn(cfunc->type));
	        return;
	}
	p = cast(p, ty);
	if (retv)
	        {
		        if (iscallb(p))
		                p = tree(RIGHT, p->type,
		                        tree(CALL+B, p->type,
		                                p->kids[0]->kids[0], idtree(retv)),
		                        rvalue(idtree(retv)));
		        else
		                p = asgntree(ASGN, rvalue(idtree(retv)), p);
		        walk(p, 0, 0);
		        if (events.returns)
		                apply(events.returns, cfunc, rvalue(idtree(retv)));
		        return;
		}
	if (events.returns)
	        {
		        Symbol t1 = genident(AUTO, p->type, level);
		        addlocal(t1);
		        walk(asgn(t1, p), 0, 0);
		        apply(events.returns, cfunc, idtree(t1));
		        p = idtree(t1);
		}
	if (!isfloat(p->type))
	        p = cast(p, promote(p->type));
	if (isptr(p->type))
	        {
		        Symbol q = localaddr(p);
		        if (q && (q->computed || q->generated))
		                warning("pointer to a %s is an illegal return value\n",
		                        q->scope == PARAM ? "parameter" : "local");
		        else if (q)
		                warning("pointer to %s `%s' is an illegal return value\n",
		                        q->scope == PARAM ? "parameter" : "local", q->name);
		}
	walk(tree(mkop(RET,p->type), p->type, p, NULL), 0, 0);
}
void definelab(int lab) {
        Code cp;
        Symbol p = findlabel(lab);

        assert(lab);
        walk(NULL, 0, 0);
        code(Label)->u.forest = newnode(LABEL+V, NULL, NULL, p);
        for (cp = codelist->prev; cp->kind <= Label; )
                cp = cp->prev;
        while (   cp->kind == Jump
	       && cp->u.forest->kids[0]
	       && specific(cp->u.forest->kids[0]->op) == ADDRG+P
	       && cp->u.forest->kids[0]->syms[0] == p) {
                assert(cp->u.forest->kids[0]->syms[0]->u.l.label == lab);
                p->ref--;
                assert(cp->next);
		assert(cp->prev);
		cp->prev->next = cp->next;
		cp->next->prev = cp->prev;
		cp = cp->prev;
                while (cp->kind <= Label)
                        cp = cp->prev;
        }
}
Node jump(int lab) {
        Symbol p = findlabel(lab);

        p->ref++;
        return newnode(JUMP+V, newnode(ADDRG+ttob(voidptype), NULL, NULL, p),
                NULL, NULL);
}
void branch(int lab) {
        Code cp;
        Symbol p = findlabel(lab);

        assert(lab);
        walk(NULL, 0, 0);
        code(Label)->u.forest = jump(lab);
        for (cp = codelist->prev; cp->kind < Label; )
                cp = cp->prev;
        while (   cp->kind == Label
	       && cp->u.forest->op == LABEL+V
	       && !equal(cp->u.forest->syms[0], p)) {
                equatelab(cp->u.forest->syms[0], p);
                assert(cp->next);
		assert(cp->prev);
		cp->prev->next = cp->next;
		cp->next->prev = cp->prev;
		cp = cp->prev;
                while (cp->kind < Label)
                        cp = cp->prev;
        }
        if (cp->kind == Jump || cp->kind == Switch) {
	        p->ref--;
	        codelist->prev->next = NULL;
	        codelist = codelist->prev;
	} else {
	        codelist->kind = Jump;
	        if (cp->kind == Label
	        &&  cp->u.forest->op == LABEL+V
	        &&  equal(cp->u.forest->syms[0], p))
	                warning("source code specifies an infinite loop");
	}
}
void equatelab(Symbol old, Symbol new) {
        assert(old->u.l.equatedto == NULL);
        old->u.l.equatedto = new;
        new->ref++;
}
static int equal(Symbol lprime, Symbol dst) {
        assert(dst && lprime);
        for ( ; dst; dst = dst->u.l.equatedto)
                if (lprime == dst)
                        return 1;
        return 0;
}
/* dostmt - do statement while ( expression ) */
static void dostmt(int lab, Swtch swp, int lev) {
        refinc *= 10.0;
        t = gettok();
        definelab(lab);
        statement(lab, swp, lev);
        definelab(lab + 1);
        expect(WHILE);
        expect('(');
        definept(NULL);
        walk(conditional(')'), lab, 0);
        if (findlabel(lab + 2)->ref)
                definelab(lab + 2);
}

/* foldcond - check if initial test in for(e1;e2;e3) S is necessary */
static int foldcond(Tree e1, Tree e2) {
        int op = generic(e2->op);
        Symbol v;

        if (e1 == 0 || e2 == 0)
                return 0;
        if (generic(e1->op) == ASGN && isaddrop(e1->kids[0]->op)
        && generic(e1->kids[1]->op) == CNST) {
                v = e1->kids[0]->u.sym;
                e1 = e1->kids[1];
        } else
                return 0;
        if ((op==LE || op==LT || op==EQ || op==NE || op==GT || op==GE)
        && generic(e2->kids[0]->op) == INDIR
        && e2->kids[0]->kids[0]->u.sym == v
        && e2->kids[1]->op == e1->op) {
                e1 = simplify(op, e2->type, e1, e2->kids[1]);
                if (e1->op == CNST+I)
                        return e1->u.v.i;
        }
        return 0;
}

/* localaddr - returns q if p yields the address of local/parameter q; otherwise returns 0 */
static Symbol localaddr(Tree p) {
        if (p == NULL)
                return NULL;
        switch (generic(p->op)) {
        case INDIR: case CALL: case ARG:
                return NULL;
        case ADDRL: case ADDRF:
                return p->u.sym;
        case RIGHT: case ASGN:
                if (p->kids[1])
                        return localaddr(p->kids[1]);
                return localaddr(p->kids[0]);
        case COND: {
                Symbol q;
                assert(p->kids[1] && p->kids[1]->op == RIGHT);
                if ((q = localaddr(p->kids[1]->kids[0])) != NULL)
                        return q;
                return localaddr(p->kids[1]->kids[1]);
                }
        default: {
                Symbol q;
                if (p->kids[0] && (q = localaddr(p->kids[0])) != NULL)
                        return q;
                return localaddr(p->kids[1]);
                }
        }
}

/* whilestmt - while ( expression ) statement */
static void whilestmt(int lab, Swtch swp, int lev) {
        Coordinate pt;
        Tree e;

        refinc *= 10.0;
        t = gettok();
        expect('(');
        walk(NULL, 0, 0);
        pt = src;
        e = texpr(conditional, ')', FUNC);
        branch(lab + 1);
        definelab(lab);
        statement(lab, swp, lev);
        definelab(lab + 1);
        definept(&pt);
        walk(e, lab, 0);
        if (findlabel(lab + 2)->ref)
                definelab(lab + 2);
}
