Node *fold(Node *n, int foldvar)
{
Node **args, *r;
Type *t;
vlong a, b;
size_t i;
if (!n)
return NULL;
if (n->type != Nexpr)
return n;
r = NULL;
args = n->expr.args;
for (i = 0; i < n->expr.nargs; i++)
args[i] = fold(args[i], foldvar);
switch (exprop(n)) {
case Ovar:
if (foldvar && issmallconst(decls[n->expr.did]))
r = fold(decls[n->expr.did]->decl.init, foldvar);
break;
case Oadd:
/* x + 0 = 0 */
if (isval(args[0], 0))
r = args[1];
if (isval(args[1], 0))
r = args[0];
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a + b, exprtype(n));
break;
case Osub:
/* x - 0 = 0 */
if (isval(args[1], 0))
r = args[0];
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a - b, exprtype(n));
break;
case Omul:
/* 1 * x = x */
if (isval(args[0], 1))
r = args[1];
if (isval(args[1], 1))
r = args[0];
/* 0 * x = 0 */
if (isval(args[0], 0))
r = args[0];
if (isval(args[1], 0))
r = args[1];
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a * b, exprtype(n));
break;
case Odiv:
/* x/1 = x */
if (isval(args[1], 1))
r = args[0];
/* 0/x = 0 */
if (isval(args[1], 0))
r = args[1];
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a / b, exprtype(n));
break;
case Omod:
/* x%1 = x */
if (isval(args[1], 0))
r = args[0];
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a % b, exprtype(n));
break;
case Oneg:
if (islit(args[0], &a))
r = val(n->line, -a, exprtype(n));
break;
case Obsl:
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a << b, exprtype(n));
break;
case Obsr:
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a >> b, exprtype(n));
break;
case Obor:
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a | b, exprtype(n));
break;
case Oband:
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a & b, exprtype(n));
break;
case Obxor:
if (islit(args[0], &a) && islit(args[1], &b))
r = val(n->line, a ^ b, exprtype(n));
break;
case Omemb:
t = tybase(exprtype(args[0]));
/* we only fold lengths right now */
if (t->type == Tyarray && !strcmp(namestr(args[1]), "len"))
r = t->asize;
break;
case Ocast:
r = foldcast(n);
break;
default:
break;
}
if (r)
return r;
else
return n;
}
Node *fold(Node *n, int foldvar)
{
Node **args, *r;
Type *t;
vlong a, b;
size_t i;
if (!n)
return NULL;
if (n->type != Nexpr)
return n;
r = NULL;
args = n->expr.args;
if (n->expr.idx)
n->expr.idx = fold(n->expr.idx, foldvar);
for (i = 0; i < n->expr.nargs; i++)
args[i] = fold(args[i], foldvar);
switch (exprop(n)) {
case Ovar:
if (foldvar && issmallconst(decls[n->expr.did]))
r = fold(decls[n->expr.did]->decl.init, foldvar);
break;
case Oadd:
/* x + 0 = 0 */
if (isintval(args[0], 0))
r = args[1];
if (isintval(args[1], 0))
r = args[0];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a + b, exprtype(n));
break;
case Osub:
/* x - 0 = 0 */
if (isintval(args[1], 0))
r = args[0];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a - b, exprtype(n));
break;
case Omul:
/* 1 * x = x */
if (isintval(args[0], 1))
r = args[1];
if (isintval(args[1], 1))
r = args[0];
/* 0 * x = 0 */
if (isintval(args[0], 0))
r = args[0];
if (isintval(args[1], 0))
r = args[1];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a * b, exprtype(n));
break;
case Odiv:
/* x/0 = error */
if (isintval(args[1], 0))
fatal(args[1], "division by zero");
/* x/1 = x */
if (isintval(args[1], 1))
r = args[0];
/* 0/x = 0 */
if (isintval(args[1], 0))
r = args[1];
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a / b, exprtype(n));
break;
case Omod:
/* x%0 = error */
if (isintval(args[1], 0))
fatal(args[1], "division by zero");
/* x%1 = 0 */
if (isintval(args[1], 1))
r = val(n->loc, 0, exprtype(n));
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a % b, exprtype(n));
break;
case Oneg:
if (getintlit(args[0], &a))
r = val(n->loc, -a, exprtype(n));
break;
case Obsl:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a << b, exprtype(n));
break;
case Obsr:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a >> b, exprtype(n));
break;
case Obor:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a | b, exprtype(n));
break;
case Oband:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a & b, exprtype(n));
break;
case Obxor:
if (getintlit(args[0], &a) && getintlit(args[1], &b))
r = val(n->loc, a ^ b, exprtype(n));
break;
case Omemb:
t = tybase(exprtype(args[0]));
/* we only fold lengths right now */
if (t->type == Tyarray && !strcmp(namestr(args[1]), "len")) {
r = t->asize;
r->expr.type = exprtype(n);
}
break;
case Oarr:
if (n->expr.nargs > 0)
qsort(n->expr.args, n->expr.nargs, sizeof(Node*), idxcmp);
break;
case Ocast:
r = foldcast(n);
break;
default:
break;
}
if (r && n->expr.idx)
r->expr.idx = n->expr.idx;
if (r)
return r;
else
return n;
}
