Expr raise_to_integer_power(Expr e, int64_t p) {
Expr result;
if (p == 0) {
result = make_one(e.type());
} else if (p == 1) {
result = e;
} else if (p < 0) {
result = make_one(e.type()) / raise_to_integer_power(e, -p);
} else {
// p is at least 2
Expr y = raise_to_integer_power(e, p>>1);
if (p & 1) result = y*y*e;
else result = y*y;
}
return result;
}
int main(int argc, char *argv[])
{
int translit = 0;
if (argc < 2) {
printf("%s", usage_msg);
exit(1);
}
/* skip my name */
--argc, ++argv;
for (; argc; --argc, ++argv) {
if (!strcasecmp(*argv, "-t")) {
translit = 1;
continue;
}
else if (!strcasecmp(*argv, "-n")) {
translit = 0;
continue;
}
make_one(*argv, translit);
}
return 0;
}
void visit(const Variable *op) {
if (op->name == var) {
expr = make_one(op->type);
} else if (scope.contains(op->name)) {
expr = scope.get(op->name);
} else {
expr = make_zero(op->type);
}
}
Expr halide_log(Expr x_full) {
Type type = x_full.type();
internal_assert(type.element_of() == Float(32));
Expr nan = Call::make(type, "nan_f32", {}, Call::PureExtern);
Expr neg_inf = Call::make(type, "neg_inf_f32", {}, Call::PureExtern);
Expr use_nan = x_full < 0.0f; // log of a negative returns nan
Expr use_neg_inf = x_full == 0.0f; // log of zero is -inf
Expr exceptional = use_nan | use_neg_inf;
// Avoid producing nans or infs by generating ln(1.0f) instead and
// then fixing it later.
Expr patched = select(exceptional, make_one(type), x_full);
Expr reduced, exponent;
range_reduce_log(patched, &reduced, &exponent);
// Very close to the Taylor series for log about 1, but tuned to
// have minimum relative error in the reduced domain (0.75 - 1.5).
float coeff[] = {
0.05111976432738144643f,
-0.11793923497136414580f,
0.14971993724699017569f,
-0.16862004708254804686f,
0.19980668101718729313f,
-0.24991211576292837737f,
0.33333435275479328386f,
-0.50000106292873236491f,
1.0f,
0.0f
};
Expr x1 = reduced - 1.0f;
Expr result = evaluate_polynomial(x1, coeff, sizeof(coeff)/sizeof(coeff[0]));
result += cast(type, exponent) * logf(2.0);
result = select(exceptional, select(use_nan, nan, neg_inf), result);
// This introduces lots of common subexpressions
result = common_subexpression_elimination(result);
return result;
}
Expr const_true(int w) {
return make_one(UInt(1, w));
}
