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use float::Float;
use int::{CastInto, Int};
fn add<F: Float>(a: F, b: F) -> F
where
u32: CastInto<F::Int>,
F::Int: CastInto<u32>,
i32: CastInto<F::Int>,
F::Int: CastInto<i32>,
{
let one = F::Int::ONE;
let zero = F::Int::ZERO;
let bits = F::BITS.cast();
let significand_bits = F::SIGNIFICAND_BITS;
let max_exponent = F::EXPONENT_MAX;
let implicit_bit = F::IMPLICIT_BIT;
let significand_mask = F::SIGNIFICAND_MASK;
let sign_bit = F::SIGN_MASK as F::Int;
let abs_mask = sign_bit - one;
let exponent_mask = F::EXPONENT_MASK;
let inf_rep = exponent_mask;
let quiet_bit = implicit_bit >> 1;
let qnan_rep = exponent_mask | quiet_bit;
let mut a_rep = a.repr();
let mut b_rep = b.repr();
let a_abs = a_rep & abs_mask;
let b_abs = b_rep & abs_mask;
if a_abs.wrapping_sub(one) >= inf_rep - one || b_abs.wrapping_sub(one) >= inf_rep - one {
if a_abs > inf_rep {
return F::from_repr(a_abs | quiet_bit);
}
if b_abs > inf_rep {
return F::from_repr(b_abs | quiet_bit);
}
if a_abs == inf_rep {
if (a.repr() ^ b.repr()) == sign_bit {
return F::from_repr(qnan_rep);
} else {
return a;
}
}
if b_abs == inf_rep {
return b;
}
if a_abs == Int::ZERO {
if b_abs == Int::ZERO {
return F::from_repr(a.repr() & b.repr());
} else {
return b;
}
}
if b_abs == Int::ZERO {
return a;
}
}
if b_abs > a_abs {
let tmp = a_rep;
a_rep = b_rep;
b_rep = tmp;
}
let mut a_exponent: i32 = ((a_rep & exponent_mask) >> significand_bits).cast();
let mut b_exponent: i32 = ((b_rep & exponent_mask) >> significand_bits).cast();
let mut a_significand = a_rep & significand_mask;
let mut b_significand = b_rep & significand_mask;
if a_exponent == 0 {
let (exponent, significand) = F::normalize(a_significand);
a_exponent = exponent;
a_significand = significand;
}
if b_exponent == 0 {
let (exponent, significand) = F::normalize(b_significand);
b_exponent = exponent;
b_significand = significand;
}
let result_sign = a_rep & sign_bit;
let subtraction = ((a_rep ^ b_rep) & sign_bit) != zero;
a_significand = (a_significand | implicit_bit) << 3;
b_significand = (b_significand | implicit_bit) << 3;
let align = a_exponent.wrapping_sub(b_exponent).cast();
if align != Int::ZERO {
if align < bits {
let sticky =
F::Int::from_bool(b_significand << bits.wrapping_sub(align).cast() != Int::ZERO);
b_significand = (b_significand >> align.cast()) | sticky;
} else {
b_significand = one;
}
}
if subtraction {
a_significand = a_significand.wrapping_sub(b_significand);
if a_significand == Int::ZERO {
return F::from_repr(Int::ZERO);
}
if a_significand < implicit_bit << 3 {
let shift =
a_significand.leading_zeros() as i32 - (implicit_bit << 3).leading_zeros() as i32;
a_significand <<= shift;
a_exponent -= shift;
}
} else {
a_significand += b_significand;
if a_significand & implicit_bit << 4 != Int::ZERO {
let sticky = F::Int::from_bool(a_significand & one != Int::ZERO);
a_significand = a_significand >> 1 | sticky;
a_exponent += 1;
}
}
if a_exponent >= max_exponent as i32 {
return F::from_repr(inf_rep | result_sign);
}
if a_exponent <= 0 {
let shift = (1 - a_exponent).cast();
let sticky =
F::Int::from_bool((a_significand << bits.wrapping_sub(shift).cast()) != Int::ZERO);
a_significand = a_significand >> shift.cast() | sticky;
a_exponent = 0;
}
let a_significand_i32: i32 = a_significand.cast();
let round_guard_sticky: i32 = a_significand_i32 & 0x7;
let mut result = a_significand >> 3 & significand_mask;
result |= a_exponent.cast() << significand_bits;
result |= result_sign;
if round_guard_sticky > 0x4 {
result += one;
}
if round_guard_sticky == 0x4 {
result += result & one;
}
F::from_repr(result)
}
intrinsics! {
#[aapcs_on_arm]
#[arm_aeabi_alias = __aeabi_fadd]
pub extern "C" fn __addsf3(a: f32, b: f32) -> f32 {
add(a, b)
}
#[aapcs_on_arm]
#[arm_aeabi_alias = __aeabi_dadd]
pub extern "C" fn __adddf3(a: f64, b: f64) -> f64 {
add(a, b)
}
#[cfg(target_arch = "arm")]
pub extern "C" fn __addsf3vfp(a: f32, b: f32) -> f32 {
a + b
}
#[cfg(target_arch = "arm")]
pub extern "C" fn __adddf3vfp(a: f64, b: f64) -> f64 {
a + b
}
}