#include "c.h"
#include <float.h>

static char rcsid[] = "$Id: simp.nw,v 2.14 1997/05/06 00:20:47 drh Exp $";

#define foldcnst(TYPE,VAR,OP) \
        if (l->op == CNST+TYPE && r->op == CNST+TYPE) \
                return cnsttree(ty, l->u.v.VAR OP r->u.v.VAR)
#define commute(L,R) \
        if (generic(R->op) == CNST && generic(L->op) != CNST) \
                do { Tree t = L; L = R; R = t; } while(0)
#define xfoldcnst(TYPE,VAR,OP,FUNC)\
        if (l->op == CNST+TYPE && r->op == CNST+TYPE\
        && FUNC(l->u.v.VAR,r->u.v.VAR,\
                ty->u.sym->u.limits.min.VAR,\
                ty->u.sym->u.limits.max.VAR, needconst)) \
                return cnsttree(ty, l->u.v.VAR OP r->u.v.VAR)
#define xcvtcnst(FTYPE,SRC,DST,VAR,EXPR) \
        if (l->op == CNST+FTYPE) do {\
                if (needconst \
                &&  ((SRC) < DST->u.sym->u.limits.min.VAR || (SRC) > DST->u.sym->u.limits.max.VAR))\
                        warning("overflow in constant expression\n");\
                if (needconst \
                || !((SRC) < DST->u.sym->u.limits.min.VAR || (SRC) > DST->u.sym->u.limits.max.VAR))\
                        return cnsttree(ty, (EXPR)); } while(0)
#define identity(X,Y,TYPE,VAR,VAL) \
        if (X->op == CNST+TYPE && X->u.v.VAR == VAL) return Y
#define zerofield(OP,TYPE,VAR) \
        if (l->op == FIELD \
        &&  r->op == CNST+TYPE && r->u.v.VAR == 0)\
                return eqtree(OP, bittree(BAND, l->kids[0],\
                        cnsttree(unsignedtype, \
                                fieldmask(l->u.field)<<fieldright(l->u.field))), r)
#define cfoldcnst(TYPE,VAR,OP) \
        if (l->op == CNST+TYPE && r->op == CNST+TYPE) \
                return cnsttree(inttype, (long)(l->u.v.VAR OP r->u.v.VAR))
#define foldaddp(L,R,RTYPE,VAR) \
        if (L->op == CNST+P && R->op == CNST+RTYPE) { \
                Tree e = tree(CNST+P, ty, NULL, NULL);\
                e->u.v.p = (char *)L->u.v.p + R->u.v.VAR;\
                return e; }
#define ufoldcnst(TYPE,EXP) if (l->op == CNST+TYPE) return EXP
#define sfoldcnst(OP) \
        if (l->op == CNST+U && r->op == CNST+I \
        && r->u.v.i >= 0 && r->u.v.i < 8*l->type->size) \
                return cnsttree(ty, (unsigned long)(l->u.v.u OP r->u.v.i))
#define geu(L,R,V) \
        if (R->op == CNST+U && R->u.v.u == 0) do { \
                warning("result of unsigned comparison is constant\n"); \
                return tree(RIGHT, inttype, root(L), cnsttree(inttype, (long)(V))); } while(0)
#define idempotent(OP) if (l->op == OP) return l->kids[0]

int needconst;
static int addi(long x, long y, long min, long max, int needconst) {
        int cond = x == 0 || y == 0
	|| x < 0 && y < 0 && x >= min - y
	|| x < 0 && y > 0
	|| x > 0 && y < 0
	|| x > 0 && y > 0 && x <= max - y;
	if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;


}

static int addd(double x, double y, double min, double max, int needconst) {
        int cond = x == 0 || y == 0
	|| x < 0 && y < 0 && x >= min - y
	|| x < 0 && y > 0
	|| x > 0 && y < 0
	|| x > 0 && y > 0 && x <= max - y;
	if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;


}

static Tree addrtree(Tree e, int n, Type ty) {
        Symbol p = e->u.sym, q;

        NEW0(q, FUNC);
        q->name = stringd(genlabel(1));
        q->sclass = p->sclass;
        q->scope = p->scope;
        assert(isptr(ty) || isarray(ty));
        q->type = isptr(ty) ? ty->type : ty;
        q->temporary = p->temporary;
        q->generated = p->generated;
        q->addressed = p->addressed;
        q->computed = 1;
        q->defined = 1;
        q->ref = 1;
        if (p->scope  == GLOBAL
	||  p->sclass == STATIC || p->sclass == EXTERN) {
	        if (p->sclass == AUTO)
	                q->sclass = STATIC;
	        (*IR->address)(q, p, n);
	} else {
	        Code cp;
	        addlocal(p);
	        cp = code(Address);
	        cp->u.addr.sym = q;
	        cp->u.addr.base = p;
	        cp->u.addr.offset = n;
	}
        e = tree(e->op, ty, NULL, NULL);
        e->u.sym = q;
        return e;
}

/* div[id] - return 1 if min <= x/y <= max, 0 otherwise */
static int divi(long x, long y, long min, long max, int needconst) {
        int cond = y != 0 && !(x == min && y == -1);
        if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;


}

static int divd(double x, double y, double min, double max, int needconst) {
        int cond;

        if (x < 0) x = -x;
        if (y < 0) y = -y;
        cond = y != 0 && !(y < 1 && x > max*y);
        if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;

}

/* mul[id] - return 1 if min <= x*y <= max, 0 otherwise */
static int muli(long x, long y, long min, long max, int needconst) {
        int cond = x > -1 && x <= 1 || y > -1 && y <= 1
        || x < 0 && y < 0 && -x <= max/-y
	|| x < 0 && y > 0 &&  x >= min/y
	|| x > 0 && y < 0 &&  y >= min/x
	|| x > 0 && y > 0 &&  x <= max/y;
	if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;


}

static int muld(double x, double y, double min, double max, int needconst) {
        int cond = x >= -1 && x <= 1 || y >= -1 && y <= 1
        || x < 0 && y < 0 && -x <= max/-y
	|| x < 0 && y > 0 &&  x >= min/y
	|| x > 0 && y < 0 &&  y >= min/x
	|| x > 0 && y > 0 &&  x <= max/y;
	if (!cond && needconst) {
	        warning("overflow in constant expression\n");
	        cond = 1;
	}
	return cond;


}
/* sub[id] - return 1 if min <= x-y <= max, 0 otherwise */
static int subi(long x, long y, long min, long max, int needconst) {
        return addi(x, -y, min, max, needconst);
}

static int subd(double x, double y, double min, double max, int needconst) {
        return addd(x, -y, min, max, needconst);
}
Tree constexpr(int tok) {
        Tree p;

        needconst++;
        p = expr1(tok);
        needconst--;
        return p;
}

int intexpr(int tok, int n) {
        Tree p = constexpr(tok);

        needconst++;
        if (p->op == CNST+I || p->op == CNST+U)
                n = cast(p, inttype)->u.v.i;
        else
                error("integer expression must be constant\n");
        needconst--;
        return n;
}
Tree simplify(int op, Type ty, Tree l, Tree r) {
        int n;
        Tree p;

        if (optype(op) == 0)
                op = mkop(op, ty);
        switch (op) {
                case ADD+U:
		        foldcnst(U,u,+);
		        commute(r,l);
		        identity(r,l,U,u,0);
		        break;
		case ADD+I:
		        xfoldcnst(I,i,+,addi);
		        commute(r,l);
		        identity(r,l,I,i,0);
		        break;
		case CVI+I:
		        xcvtcnst(I,l->u.v.i,ty,i,(long)extend(l->u.v.i,ty));
		        break;
		case CVU+I:
		        if (l->op == CNST+U) {
		                if (needconst &&   l->u.v.u > ty->u.sym->u.limits.max.i)
		                        warning("overflow in constant expression\n");
		                if (needconst || !(l->u.v.u > ty->u.sym->u.limits.max.i))
		                        return cnsttree(ty, (long)extend(l->u.v.u,ty));
		        }
		        break;
		case CVP+U:
		        xcvtcnst(P,(unsigned long)l->u.v.p,ty,u,(unsigned long)l->u.v.p);
		        break;
		case CVU+P:
		        xcvtcnst(U,(void*)l->u.v.u,ty,p,(void*)l->u.v.u);
		        break;
		case CVP+P:
		        xcvtcnst(P,l->u.v.p,ty,p,l->u.v.p);
		        break;
		case CVI+U:
		        xcvtcnst(I,l->u.v.i,longtype,i,(unsigned long)l->u.v.i);
		        break;
		case CVU+U:
		        xcvtcnst(U,l->u.v.u,unsignedlong,u,l->u.v.u);
		        break;

		case CVI+F:
		        xcvtcnst(I,l->u.v.i,ty,d,(long double)l->u.v.i);
		case CVU+F:
		        xcvtcnst(U,l->u.v.u,ty,d,(long double)l->u.v.u);
		        break;
		case CVF+I:
		        xcvtcnst(F,l->u.v.d,ty,i,(long)l->u.v.d);
		        break;
		case CVF+F:
		        xcvtcnst(F,l->u.v.d,ty,d,l->u.v.d);
		        break;
		case BAND+U:
		        foldcnst(U,u,&);
		        commute(r,l);
		        identity(r,l,U,u,ones(8*ty->size));
		        if (r->op == CNST+U && r->u.v.u == 0)
		                return tree(RIGHT, ty, root(l), cnsttree(ty, 0));
		        break;
		case BAND+I:
		        foldcnst(I,i,&);
		        commute(r,l);
		        identity(r,l,I,i,ones(8*ty->size));
		        if (r->op == CNST+I && r->u.v.u == 0)
		                return tree(RIGHT, ty, root(l), cnsttree(ty, 0));
		        break;

		case MUL+U:
		        commute(l,r);
		        if (l->op == CNST+U && (n = ispow2(l->u.v.u)) != 0)
		                return simplify(LSH, ty, r, cnsttree(inttype, (long)n));
		        foldcnst(U,u,*);
		        identity(r,l,U,u,1);
		        break;
		case NE+I:
		        cfoldcnst(I,i,!=);
		        commute(r,l);
		        zerofield(NE,I,i);
		        break;

		case EQ+I:
		        cfoldcnst(I,i,==);
		        commute(r,l);
		        zerofield(EQ,I,i);
		        break;
		case ADD+P:
		        foldaddp(l,r,I,i);
		        foldaddp(l,r,U,u);
		        foldaddp(r,l,I,i);
		        foldaddp(r,l,U,u);
		        commute(r,l);
		        identity(r,retype(l,ty),I,i,0);
		        identity(r,retype(l,ty),U,u,0);
		        if (isaddrop(l->op)
			&& (r->op == CNST+I || r->op == CNST+U))
			        return addrtree(l, cast(r, inttype)->u.v.i, ty);
			if (l->op == ADD+P && isaddrop(l->kids[1]->op)
			&& (r->op == CNST+I || r->op == CNST+U))
			        return simplify(ADD+P, ty, l->kids[0],
			                addrtree(l->kids[1], cast(r, inttype)->u.v.i, ty));
			if ((l->op == ADD+I || l->op == SUB+I)
			&& l->kids[1]->op == CNST+I && isaddrop(r->op))
			        return simplify(ADD+P, ty, l->kids[0],
			                simplify(generic(l->op)+P, ty, r, l->kids[1]));
			if (l->op == ADD+P && generic(l->kids[1]->op) == CNST
			&& generic(r->op) == CNST)
			        return simplify(ADD+P, ty, l->kids[0],
			                simplify(ADD, l->kids[1]->type, l->kids[1], r));
			if (l->op == ADD+I && generic(l->kids[1]->op) == CNST
			&&  r->op == ADD+P && generic(r->kids[1]->op) == CNST)
			        return simplify(ADD+P, ty, l->kids[0],
			                simplify(ADD+P, ty, r->kids[0],
			                simplify(ADD, r->kids[1]->type, l->kids[1], r->kids[1])));
			if (l->op == RIGHT && l->kids[1])
			        return tree(RIGHT, ty, l->kids[0],
			                simplify(ADD+P, ty, l->kids[1], r));
			else if (l->op == RIGHT && l->kids[0])
			        return tree(RIGHT, ty,
			                simplify(ADD+P, ty, l->kids[0], r), NULL);
		        break;

		case ADD+F:
		        xfoldcnst(F,d,+,addd);
		        commute(r,l);
		        break;
		case AND+I:
		        op = AND;
		        ufoldcnst(I,l->u.v.i ? cond(r) : l);    /* 0&&r => 0, 1&&r => r */
		        break;
		case OR+I:
		        op = OR;
		        /* 0||r => r, 1||r => 1 */
		        ufoldcnst(I,l->u.v.i ? cnsttree(ty, 1L) : cond(r));
		        break;
		case BCOM+I:
		        ufoldcnst(I,cnsttree(ty, (long)extend((~l->u.v.i)&ones(8*ty->size), ty)));
		        idempotent(BCOM+U);
		        break;
		case BCOM+U:
		        ufoldcnst(U,cnsttree(ty, (unsigned long)((~l->u.v.u)&ones(8*ty->size))));
		        idempotent(BCOM+U);
		        break;
		case BOR+U:
		        foldcnst(U,u,|);
		        commute(r,l);
		        identity(r,l,U,u,0);
		        break;
		case BOR+I:
		        foldcnst(I,i,|);
		        commute(r,l);
		        identity(r,l,I,i,0);
		        break;
		case BXOR+U:
		        foldcnst(U,u,^);
		        commute(r,l);
		        identity(r,l,U,u,0);
		        break;
		case BXOR+I:
		        foldcnst(I,i,^);
		        commute(r,l);
		        identity(r,l,I,i,0);
		        break;
		case DIV+F:
		        xfoldcnst(F,d,/,divd);
		        break;
		case DIV+I:
		        identity(r,l,I,i,1);
		        if (r->op == CNST+I && r->u.v.i == 0
		        ||  l->op == CNST+I && l->u.v.i == ty->u.sym->u.limits.min.i
		        &&  r->op == CNST+I && r->u.v.i == -1)
		                break;
		        xfoldcnst(I,i,/,divi);
		        break;
		case DIV+U:             
		        identity(r,l,U,u,1);
		        if (r->op == CNST+U && r->u.v.u == 0)
		                break;
		        if (r->op == CNST+U && (n = ispow2(r->u.v.u)) != 0)
		                return simplify(RSH, ty, l, cnsttree(inttype, (long)n));
		        foldcnst(U,u,/);
		        break;
		case EQ+F:
		        cfoldcnst(F,d,==);
		        commute(r,l);
		        break;
		case EQ+U:
		        cfoldcnst(U,u,==);
		        commute(r,l);
		        zerofield(EQ,U,u);
		        break;
		case GE+F: cfoldcnst(F,d,>=); break;
		case GE+I: cfoldcnst(I,i,>=); break;
		case GE+U:
		        geu(l,r,1);     /* l >= 0 => (l,1) */
		        cfoldcnst(U,u,>=);
		        if (l->op == CNST+U && l->u.v.u == 0)   /* 0 >= r => r == 0 */
		                return eqtree(EQ, r, l);
		        break;
		case GT+F: cfoldcnst(F,d, >); break;
		case GT+I: cfoldcnst(I,i, >); break;
		case GT+U:
		        geu(r,l,0);     /* 0 > r => (r,0) */
		        cfoldcnst(U,u, >);
		        if (r->op == CNST+U && r->u.v.u == 0)   /* l > 0 => l != 0 */
		                return eqtree(NE, l, r);
		        break;
		case LE+F: cfoldcnst(F,d,<=); break;
		case LE+I: cfoldcnst(I,i,<=); break;
		case LE+U:
		        geu(r,l,1);     /* 0 <= r => (r,1) */
		        cfoldcnst(U,u,<=);
		        if (r->op == CNST+U && r->u.v.u == 0)   /* l <= 0 => l == 0 */
		                return eqtree(EQ, l, r);
		        break;
		case LSH+I:
		        identity(r,l,I,i,0);
		        if (l->op == CNST+I && r->op == CNST+I
		        && r->u.v.i >= 0 && r->u.v.i < 8*l->type->size
		        && muli(l->u.v.i, 1<<r->u.v.i, ty->u.sym->u.limits.min.i, ty->u.sym->u.limits.max.i, needconst))
		                return cnsttree(ty, (long)(l->u.v.i<<r->u.v.i));
		        if (r->op == CNST+I && (r->u.v.i >= 8*ty->size || r->u.v.i < 0)) {
			        warning("shifting an `%t' by %d bits is undefined\n", ty, r->u.v.i);
			        break;
			}

		        break;
		case LSH+U:
		        identity(r,l,I,i,0);
		        sfoldcnst(<<);
		        if (r->op == CNST+I && (r->u.v.i >= 8*ty->size || r->u.v.i < 0)) {
			        warning("shifting an `%t' by %d bits is undefined\n", ty, r->u.v.i);
			        break;
			}

		        break;

		case LT+F: cfoldcnst(F,d, <); break;
		case LT+I: cfoldcnst(I,i, <); break;
		case LT+U:
		        geu(l,r,0);     /* l < 0 => (l,0) */
		        cfoldcnst(U,u, <);
		        if (l->op == CNST+U && l->u.v.u == 0)   /* 0 < r => r != 0 */
		                return eqtree(NE, r, l);
		        break;
		case MOD+I:
		        if (r->op == CNST+I && r->u.v.i == 1)   /* l%1 => (l,0) */
		                return tree(RIGHT, ty, root(l), cnsttree(ty, 0L));
		        if (r->op == CNST+I && r->u.v.i == 0
		        ||  l->op == CNST+I && l->u.v.i == ty->u.sym->u.limits.min.i
		        &&  r->op == CNST+I && r->u.v.i == -1)
		                break;
		        xfoldcnst(I,i,%,divi);
		        break;
		case MOD+U:             
		        if (r->op == CNST+U && ispow2(r->u.v.u)) /* l%2^n => l&(2^n-1) */
		                return bittree(BAND, l, cnsttree(ty, r->u.v.u - 1));
		        if (r->op == CNST+U && r->u.v.u == 0)
		                break;
		        foldcnst(U,u,%);
		        break;
		case MUL+F:
		        xfoldcnst(F,d,*,muld);
		        commute(l,r);
		        break;
		case MUL+I:
		        commute(l,r);
		        xfoldcnst(I,i,*,muli);
		        if (l->op == CNST+I && r->op == ADD+I && r->kids[1]->op == CNST+I)
		                /* c1*(x + c2) => c1*x + c1*c2 */
		                return simplify(ADD, ty, simplify(MUL, ty, l, r->kids[0]),
		                        simplify(MUL, ty, l, r->kids[1]));
		        if (l->op == CNST+I && r->op == SUB+I && r->kids[1]->op == CNST+I)
		                /* c1*(x - c2) => c1*x - c1*c2 */
		                return simplify(SUB, ty, simplify(MUL, ty, l, r->kids[0]),
		                        simplify(MUL, ty, l, r->kids[1]));
		        if (l->op == CNST+I && l->u.v.i > 0 && (n = ispow2(l->u.v.i)) != 0)
		                /* 2^n * r => r<<n */
		                return simplify(LSH, ty, r, cnsttree(inttype, (long)n));
		        identity(r,l,I,i,1);
		        break;
		case NE+F:
		        cfoldcnst(F,d,!=);
		        commute(r,l);
		        break;
		case NE+U:
		        cfoldcnst(U,u,!=);
		        commute(r,l);
		        zerofield(NE,U,u);
		        break;
		case NEG+F:
		        ufoldcnst(F,cnsttree(ty, -l->u.v.d));
		        idempotent(NEG+F);
		        break;
		case NEG+I:
		        if (l->op == CNST+I) {
		                if (needconst && l->u.v.i == ty->u.sym->u.limits.min.i)
		                        warning("overflow in constant expression\n");
		                if (needconst || l->u.v.i != ty->u.sym->u.limits.min.i)
		                        return cnsttree(ty, -l->u.v.i);
		        }
		        idempotent(NEG+I);
		        break;
		case NOT+I:
		        op = NOT;
		        ufoldcnst(I,cnsttree(ty, !l->u.v.i));
		        break;
		case RSH+I:
		        identity(r,l,I,i,0);
		        if (l->op == CNST+I && r->op == CNST+I
		        && r->u.v.i >= 0 && r->u.v.i < 8*l->type->size) {
		                long n = l->u.v.i>>r->u.v.i;
		                if (l->u.v.i < 0)
		                        n |= ~0UL<<(8*l->type->size - r->u.v.i);
		                return cnsttree(ty, n);
		        }
		        if (r->op == CNST+I && (r->u.v.i >= 8*ty->size || r->u.v.i < 0)) {
			        warning("shifting an `%t' by %d bits is undefined\n", ty, r->u.v.i);
			        break;
			}

		        break;
		case RSH+U:
		        identity(r,l,I,i,0);
		        sfoldcnst(>>);
		        if (r->op == CNST+I && (r->u.v.i >= 8*ty->size || r->u.v.i < 0)) {
			        warning("shifting an `%t' by %d bits is undefined\n", ty, r->u.v.i);
			        break;
			}

		        break;
		case SUB+F:
		        xfoldcnst(F,d,-,subd);
		        break;
		case SUB+I:
		        xfoldcnst(I,i,-,subi);
		        identity(r,l,I,i,0);
		        break;
		case SUB+U:
		        foldcnst(U,u,-);
		        identity(r,l,U,u,0);
		        break;
		case SUB+P:
		        if (l->op == CNST+P && r->op == CNST+P)
		                return cnsttree(ty, (char *)l->u.v.p - (char *)r->u.v.p);
		        if (r->op == CNST+I || r->op == CNST+U)
		                return simplify(ADD, ty, l,
		                        cnsttree(inttype, r->op == CNST+I ? -r->u.v.i : -(int)r->u.v.u));
		        if (isaddrop(l->op) && r->op == ADD+I && r->kids[1]->op == CNST+I)
		                /* l - (x + c) => l-c - x */
		                return simplify(SUB, ty,
		                        simplify(SUB, ty, l, r->kids[1]), r->kids[0]);
		        break;
		default:assert(0);
        }
        return tree(op, ty, l, r);
}
/* ispow2 - if u > 1 && u == 2^n, return n, otherwise return 0 */
int ispow2(unsigned long u) {
        int n;

        if (u > 1 && (u&(u-1)) == 0)
                for (n = 0; u; u >>= 1, n++)
                        if (u&1)
                                return n;
        return 0;
}

