#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;
}

