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fixed
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optimization: do not mix sar and shr in fixed conversion

This commit is contained in:
Trevor Spiteri 2019-02-02 21:33:01 +01:00
parent 8bfc52c3ab
commit 8209c4466d
1 changed files with 14 additions and 11 deletions
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25
src/sealed_int.rs
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@ -204,18 +204,17 @@ macro_rules! sealed_int {
let src_bits = Self::NBITS as i32;
let dst_bits = (dst_frac_bits + dst_int_bits) as i32;
if self >= 0 {
return SealedInt::to_fixed_dir_overflow(
self as $Unsigned,
src_frac_bits,
dst_frac_bits,
dst_int_bits,
);
if self == 0 {
return (Widest::Unsigned(0), Ordering::Equal, false);
}
let leading_ones = (!self).leading_zeros();
let need_to_shr = src_frac_bits - dst_frac_bits as i32;
let overflow = src_bits - dst_bits > need_to_shr + leading_ones as i32 - 1;
let leading = if self >= 0 {
self.leading_zeros()
} else {
(!self).leading_zeros() - 1
};
let overflow = src_bits - dst_bits > need_to_shr + leading as i32;
let bits_128 = i128::from(self);
let (bits, lost_bits) = match need_to_shr {
-0x7fff_ffff..=-128 => (0, false),
@ -225,11 +224,15 @@ macro_rules! sealed_int {
let shifted = bits_128 >> need_to_shr;
(shifted, shifted << need_to_shr != bits_128)
}
128..=0x7fff_ffff => (-1, true),
128..=0x7fff_ffff => (bits_128 >> 127, true),
_ => unreachable!(),
};
let dir = if lost_bits { Ordering::Less } else { Ordering::Equal };
(Widest::Negative(bits), dir, overflow)
if self >= 0 {
(Widest::Unsigned(bits as u128), dir, overflow)
} else {
(Widest::Negative(bits), dir, overflow)
}
}
}
};