Function float_to_lns

external/astc-encoder/Source/astcenc_vecmathlib.h:558–596

* @brief Convert float to 16-bit LNS. */

 * @brief Convert float to 16-bit LNS.
 */
static ASTCENC_SIMD_INLINE vfloat4 float_to_lns(vfloat4 a)
{
	vint4 exp;
	vfloat4 mant = frexp(a, exp);

	// Do these early before we start messing about ...
	vmask4 mask_underflow_nan = ~(a > vfloat4(1.0f / 67108864.0f));
	vmask4 mask_infinity = a >= vfloat4(65536.0f);

	// If input is smaller than 2^-14, multiply by 2^25 and don't bias.
	vmask4 exp_lt_m13 = exp < vint4(-13);

	vfloat4 a1a = a * 33554432.0f;
	vint4 expa = vint4::zero();

	vfloat4 a1b = (mant - 0.5f) * 4096;
	vint4 expb = exp + 14;

	a = select(a1b, a1a, exp_lt_m13);
	exp = select(expb, expa, exp_lt_m13);

	vmask4 a_lt_384 = a < vfloat4(384.0f);
	vmask4 a_lt_1408 = a <= vfloat4(1408.0f);

	vfloat4 a2a = a * (4.0f / 3.0f);
	vfloat4 a2b = a + 128.0f;
	vfloat4 a2c = (a + 512.0f) * (4.0f / 5.0f);

	a = a2c;
	a = select(a, a2b, a_lt_1408);
	a = select(a, a2a, a_lt_384);

	a = a + (int_to_float(exp) * 2048.0f) + 1.0f;

	a = select(a, vfloat4(65535.0f), mask_infinity);
	a = select(a, vfloat4::zero(), mask_underflow_nan);

	return a;
}

namespace astc
{