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Refactor float builtins to use associated consts

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This commit is contained in:
est31 2017-09-13 22:08:15 +02:00
parent c9a261895e
commit 9bdedec38e
4 changed files with 56 additions and 80 deletions
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4
src/float/add.rs
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@ -10,8 +10,8 @@ macro_rules! add {
let one = Wrapping(1 as <$ty as Float>::Int);
let zero = Wrapping(0 as <$ty as Float>::Int);
let bits = Wrapping(<$ty>::bits() as <$ty as Float>::Int);
let significand_bits = Wrapping(<$ty>::significand_bits() as <$ty as Float>::Int);
let bits = Wrapping(<$ty>::BITS as <$ty as Float>::Int);
let significand_bits = Wrapping(<$ty>::SIGNIFICAND_BITS as <$ty as Float>::Int);
let exponent_bits = bits - significand_bits - one;
let max_exponent = (one << exponent_bits.0 as usize) - one;

12
src/float/conv.rs
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@ -8,8 +8,8 @@ macro_rules! int_to_float {
return 0.0
}
let mant_dig = <$fty>::significand_bits() + 1;
let exponent_bias = <$fty>::exponent_bias();
let mant_dig = <$fty>::SIGNIFICAND_BITS + 1;
let exponent_bias = <$fty>::EXPONENT_BIAS;
let n = <$ity>::BITS;
let (s, a) = i.extract_sign();
@ -145,9 +145,9 @@ macro_rules! float_to_int {
let fixint_bits = <$ity>::BITS as usize;
let fixint_unsigned = fixint_min == 0;
let sign_bit = <$fty>::sign_mask();
let significand_bits = <$fty>::significand_bits() as usize;
let exponent_bias = <$fty>::exponent_bias() as usize;
let sign_bit = <$fty>::SIGN_MASK;
let significand_bits = <$fty>::SIGNIFICAND_BITS as usize;
let exponent_bias = <$fty>::EXPONENT_BIAS as usize;
//let exponent_max = <$fty>::exponent_max() as usize;
// Break a into sign, exponent, significand
@ -157,7 +157,7 @@ macro_rules! float_to_int {
// this is used to work around -1 not being available for unsigned
let sign = if (a_rep & sign_bit) == 0 { Sign::Positive } else { Sign::Negative };
let mut exponent = (a_abs >> significand_bits) as usize;
let significand = (a_abs & <$fty>::significand_mask()) | <$fty>::implicit_bit();
let significand = (a_abs & <$fty>::SIGNIFICAND_MASK) | <$fty>::IMPLICIT_BIT;
// if < 1 or unsigned & negative
if exponent < exponent_bias ||

116
src/float/mod.rs
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@ -1,5 +1,7 @@
use core::mem;
use super::int::Int;
pub mod conv;
pub mod add;
pub mod pow;
@ -8,39 +10,34 @@ pub mod sub;
/// Trait for some basic operations on floats
pub trait Float: Sized + Copy {
/// A uint of the same with as the float
type Int;
type Int: Int;
/// Returns the bitwidth of the float type
fn bits() -> u32;
/// The bitwidth of the float type
const BITS: u32;
/// Returns the bitwidth of the significand
fn significand_bits() -> u32;
/// The bitwidth of the significand
const SIGNIFICAND_BITS: u32;
/// Returns the bitwidth of the exponent
fn exponent_bits() -> u32 {
Self::bits() - Self::significand_bits() - 1
}
/// Returns the maximum value of the exponent
fn exponent_max() -> u32 {
(1 << Self::exponent_bits()) - 1
}
/// The bitwidth of the exponent
const EXPONENT_BITS: u32 = Self::BITS - Self::SIGNIFICAND_BITS - 1;
/// Returns the exponent bias value
fn exponent_bias() -> u32 {
Self::exponent_max() >> 1
}
/// The maximum value of the exponent
const EXPONENT_MAX: u32 = (1 << Self::EXPONENT_BITS) - 1;
/// Returns a mask for the sign bit
fn sign_mask() -> Self::Int;
/// The exponent bias value
const EXPONENT_BIAS: u32 = Self::EXPONENT_MAX >> 1;
/// Returns a mask for the significand
fn significand_mask() -> Self::Int;
/// A mask for the sign bit
const SIGN_MASK: Self::Int;
// Returns the implicit bit of the float format
fn implicit_bit() -> Self::Int;
/// A mask for the significand
const SIGNIFICAND_MASK: Self::Int;
/// Returns a mask for the exponent
fn exponent_mask() -> Self::Int;
// The implicit bit of the float format
const IMPLICIT_BIT: Self::Int;
/// A mask for the exponent
const EXPONENT_MASK: Self::Int;
/// Returns `self` transmuted to `Self::Int`
fn repr(self) -> Self::Int;
@ -65,24 +62,14 @@ pub trait Float: Sized + Copy {
// https://github.com/rust-lang/rfcs/issues/1424
impl Float for f32 {
type Int = u32;
fn bits() -> u32 {
32
}
fn significand_bits() -> u32 {
23
}
fn implicit_bit() -> Self::Int {
1 << Self::significand_bits()
}
fn sign_mask() -> Self::Int {
1 << (Self::bits() - 1)
}
fn significand_mask() -> Self::Int {
(1 << Self::significand_bits()) - 1
}
fn exponent_mask() -> Self::Int {
!(Self::sign_mask() | Self::significand_mask())
}
const BITS: u32 = 32;
const SIGNIFICAND_BITS: u32 = 23;
const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1);
const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1;
const IMPLICIT_BIT: Self::Int = 1 << Self::SIGNIFICAND_BITS;
const EXPONENT_MASK: Self::Int = !(Self::SIGN_MASK | Self::SIGNIFICAND_MASK);
fn repr(self) -> Self::Int {
unsafe { mem::transmute(self) }
}
@ -98,37 +85,26 @@ impl Float for f32 {
unsafe { mem::transmute(a) }
}
fn from_parts(sign: bool, exponent: Self::Int, significand: Self::Int) -> Self {
Self::from_repr(((sign as Self::Int) << (Self::bits() - 1)) |
((exponent << Self::significand_bits()) & Self::exponent_mask()) |
(significand & Self::significand_mask()))
Self::from_repr(((sign as Self::Int) << (Self::BITS - 1)) |
((exponent << Self::SIGNIFICAND_BITS) & Self::EXPONENT_MASK) |
(significand & Self::SIGNIFICAND_MASK))
}
fn normalize(significand: Self::Int) -> (i32, Self::Int) {
let shift = significand.leading_zeros()
.wrapping_sub((1u32 << Self::significand_bits()).leading_zeros());
.wrapping_sub((1u32 << Self::SIGNIFICAND_BITS).leading_zeros());
(1i32.wrapping_sub(shift as i32), significand << shift as Self::Int)
}
}
impl Float for f64 {
type Int = u64;
fn bits() -> u32 {
64
}
fn significand_bits() -> u32 {
52
}
// Returns the implicit bit of the float format
fn implicit_bit() -> Self::Int {
1 << Self::significand_bits()
}
fn sign_mask() -> Self::Int {
1 << (Self::bits() - 1)
}
fn significand_mask() -> Self::Int {
(1 << Self::significand_bits()) - 1
}
fn exponent_mask() -> Self::Int {
!(Self::sign_mask() | Self::significand_mask())
}
const BITS: u32 = 64;
const SIGNIFICAND_BITS: u32 = 52;
const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1);
const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1;
const IMPLICIT_BIT: Self::Int = 1 << Self::SIGNIFICAND_BITS;
const EXPONENT_MASK: Self::Int = !(Self::SIGN_MASK | Self::SIGNIFICAND_MASK);
fn repr(self) -> Self::Int {
unsafe { mem::transmute(self) }
}
@ -144,13 +120,13 @@ impl Float for f64 {
unsafe { mem::transmute(a) }
}
fn from_parts(sign: bool, exponent: Self::Int, significand: Self::Int) -> Self {
Self::from_repr(((sign as Self::Int) << (Self::bits() - 1)) |
((exponent << Self::significand_bits()) & Self::exponent_mask()) |
(significand & Self::significand_mask()))
Self::from_repr(((sign as Self::Int) << (Self::BITS - 1)) |
((exponent << Self::SIGNIFICAND_BITS) & Self::EXPONENT_MASK) |
(significand & Self::SIGNIFICAND_MASK))
}
fn normalize(significand: Self::Int) -> (i32, Self::Int) {
let shift = significand.leading_zeros()
.wrapping_sub((1u64 << Self::significand_bits()).leading_zeros());
.wrapping_sub((1u64 << Self::SIGNIFICAND_BITS).leading_zeros());
(1i32.wrapping_sub(shift as i32), significand << shift as Self::Int)
}
}

4
src/float/sub.rs
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@ -3,11 +3,11 @@ use float::Float;
intrinsics! {
#[arm_aeabi_alias = __aeabi_fsub]
pub extern "C" fn __subsf3(a: f32, b: f32) -> f32 {
a + f32::from_repr(b.repr() ^ f32::sign_mask())
a + f32::from_repr(b.repr() ^ f32::SIGN_MASK)
}
#[arm_aeabi_alias = __aeabi_dsub]
pub extern "C" fn __subdf3(a: f64, b: f64) -> f64 {
a + f64::from_repr(b.repr() ^ f64::sign_mask())
a + f64::from_repr(b.repr() ^ f64::SIGN_MASK)
}
}