simp.c

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


#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 (!explicitCast\
        &&  ((SRC) < DST->u.sym->u.limits.min.VAR || (SRC) > DST->u.sym->u.limits.max.VAR))\
            warning("overflow in converting constant expression from `%t' to `%t'\n", l->type, DST);\
        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, \
                (unsigned long)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;
int explicitCast;
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, long n, Type ty) {
    Symbol p = e->u.sym, q;

    if (p->scope  == GLOBAL
    ||  p->sclass == STATIC || p->sclass == EXTERN)
        NEW0(q, PERM);
    else
        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 (!explicitCast && l->u.v.u > ty->u.sym->u.limits.max.i)
                    warning("overflow in converting constant expression from `%t' to `%t'\n", l->type, ty);
                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,ty,u,((unsigned long)l->u.v.i)&ones(8*ty->size));
            break;
        case CVU+U:
            xcvtcnst(U,l->u.v.u,ty,u,l->u.v.u&ones(8*ty->size));
            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: {
            float d;
            if (l->op == CNST+F)
                if (l->u.v.d < ty->u.sym->u.limits.min.d)
                    d = ty->u.sym->u.limits.min.d;
                else if (l->u.v.d > ty->u.sym->u.limits.max.d)
                    d = ty->u.sym->u.limits.max.d;
                else
                    d = l->u.v.d;
            xcvtcnst(F,l->u.v.d,ty,d,(long double)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, 0UL));
            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, 0L));
            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->u.v.i <= longtype->u.sym->u.limits.max.i
                && r->u.v.i >= longtype->u.sym->u.limits.min.i
            || r->op == CNST+U && r->u.v.u <= longtype->u.sym->u.limits.max.i))
                return addrtree(l, cast(r, longtype)->u.v.i, ty);
            if (l->op == ADD+P && isaddrop(l->kids[1]->op)
            && (r->op == CNST+I && r->u.v.i <= longtype->u.sym->u.limits.max.i
                && r->u.v.i >= longtype->u.sym->u.limits.min.i
            ||  r->op == CNST+U && r->u.v.u <= longtype->u.sym->u.limits.max.i))
                return simplify(ADD+P, ty, l->kids[0],
                    addrtree(l->kids[1], cast(r, longtype)->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, (long)((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 : -(long)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;
}

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