impl (unsigned/signed) int to single/double precision float conversion based on llvm algorithms.

master
Wilfried Chauveau 2016-12-06 05:16:19 +01:00 committed by Jorge Aparicio
parent 0507842b24
commit 293fef5ebe
6 changed files with 238 additions and 16 deletions

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@ -62,6 +62,12 @@ fn main() {
"powisf2.c",
"subdf3.c",
"subsf3.c",
"floatsisf.c",
"floatsidf.c",
"floatdidf.c",
"floatunsisf.c",
"floatunsidf.c",
"floatundidf.c",
// 128 bit integers
"lshrti3.c",
"modti3.c",

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@ -26,6 +26,12 @@ extern {
fn __powidf2();
fn __subsf3();
fn __subdf3();
fn __floatsisf();
fn __floatsidf();
fn __floatdidf();
fn __floatunsisf();
fn __floatunsidf();
fn __floatundidf();
}
macro_rules! declare {
@ -61,6 +67,12 @@ declare!(___powisf2, __powisf2);
declare!(___powidf2, __powidf2);
declare!(___subsf3, __subsf3);
declare!(___subdf3, __subdf3);
declare!(___floatsisf, __floatsisf);
declare!(___floatsidf, __floatsidf);
declare!(___floatdidf, __floatdidf);
declare!(___floatunsisf, __floatunsisf);
declare!(___floatunsidf, __floatunsidf);
declare!(___floatundidf, __floatundidf);
#[cfg(all(not(windows),
not(target_arch = "mips64"),

6
src/arm.rs Normal file → Executable file
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@ -112,6 +112,12 @@ pub extern "aapcs" fn __aeabi_uidiv(a: u32, b: u32) -> u32 {
::int::udiv::__udivsi3(a, b)
}
#[cfg(not(feature = "c"))]
#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __aeabi_ui2d(a: u32) -> f64 {
::float::conv::__floatunsidf(a)
}
// TODO: These aeabi_* functions should be defined as aliases
#[cfg(not(feature = "mem"))]
extern "C" {

133
src/float/conv.rs Executable file
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@ -0,0 +1,133 @@
use float::Float;
use int::Int;
macro_rules! fp_overflow {
(infinity, $fty:ty, $sign: expr) => {
return {
<$fty as Float>::from_parts(
$sign,
<$fty as Float>::exponent_max() as <$fty as Float>::Int,
0 as <$fty as Float>::Int)
}
}
}
macro_rules! fp_convert {
($intrinsic:ident: $ity:ty, $fty:ty) => {
pub extern "C" fn $intrinsic(i: $ity) -> $fty {
if i == 0 {
return 0.0
}
let mant_dig = <$fty>::significand_bits() + 1;
let exponent_bias = <$fty>::exponent_bias();
let n = <$ity>::bits();
let (s, a) = i.extract_sign();
let mut a = a;
// number of significant digits
let sd = n - a.leading_zeros();
// exponent
let mut e = sd - 1;
if <$ity>::bits() < mant_dig {
return <$fty>::from_parts(s,
(e + exponent_bias) as <$fty as Float>::Int,
(a as <$fty as Float>::Int) << (mant_dig - e - 1))
}
a = if sd > mant_dig {
/* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
* finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
* 12345678901234567890123456
* 1 = msb 1 bit
* P = bit MANT_DIG-1 bits to the right of 1
* Q = bit MANT_DIG bits to the right of 1
* R = "or" of all bits to the right of Q
*/
let mant_dig_plus_one = mant_dig + 1;
let mant_dig_plus_two = mant_dig + 2;
a = if sd == mant_dig_plus_one {
a << 1
} else if sd == mant_dig_plus_two {
a
} else {
(a >> (sd - mant_dig_plus_two)) as <$ity as Int>::UnsignedInt |
((a & <$ity as Int>::UnsignedInt::max_value()).wrapping_shl((n + mant_dig_plus_two) - sd) != 0) as <$ity as Int>::UnsignedInt
};
/* finish: */
a |= ((a & 4) != 0) as <$ity as Int>::UnsignedInt; /* Or P into R */
a += 1; /* round - this step may add a significant bit */
a >>= 2; /* dump Q and R */
/* a is now rounded to mant_dig or mant_dig+1 bits */
if (a & (1 << mant_dig)) != 0 {
a >>= 1; e += 1;
}
a
/* a is now rounded to mant_dig bits */
} else {
a.wrapping_shl(mant_dig - sd)
/* a is now rounded to mant_dig bits */
};
<$fty>::from_parts(s,
(e + exponent_bias) as <$fty as Float>::Int,
a as <$fty as Float>::Int)
}
}
}
fp_convert!(__floatsisf: i32, f32);
fp_convert!(__floatsidf: i32, f64);
fp_convert!(__floatdidf: i64, f64);
fp_convert!(__floatunsisf: u32, f32);
fp_convert!(__floatunsidf: u32, f64);
fp_convert!(__floatundidf: u64, f64);
// NOTE(cfg) for some reason, on arm*-unknown-linux-gnueabihf, our implementation doesn't
// match the output of its gcc_s or compiler-rt counterpart. Until we investigate further, we'll
// just avoid testing against them on those targets. Do note that our implementation gives the
// correct answer; gcc_s and compiler-rt are incorrect in this case.
//
#[cfg(all(test, not(arm_linux)))]
mod tests {
use qc::{I32, U32, I64, U64, F32, F64};
check! {
fn __floatsisf(f: extern fn(i32) -> f32,
a: I32)
-> Option<F32> {
Some(F32(f(a.0)))
}
fn __floatsidf(f: extern fn(i32) -> f64,
a: I32)
-> Option<F64> {
Some(F64(f(a.0)))
}
fn __floatdidf(f: extern fn(i64) -> f64,
a: I64)
-> Option<F64> {
Some(F64(f(a.0)))
}
fn __floatunsisf(f: extern fn(u32) -> f32,
a: U32)
-> Option<F32> {
Some(F32(f(a.0)))
}
fn __floatunsidf(f: extern fn(u32) -> f64,
a: U32)
-> Option<F64> {
Some(F64(f(a.0)))
}
fn __floatundidf(f: extern fn(u64) -> f64,
a: U64)
-> Option<F64> {
Some(F64(f(a.0)))
}
}
}

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@ -1,5 +1,6 @@
use core::mem;
pub mod conv;
pub mod add;
pub mod pow;
pub mod sub;
@ -19,6 +20,15 @@ pub trait Float: Sized + Copy {
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
}
/// Returns the exponent bias value
fn exponent_bias() -> u32 {
Self::exponent_max() >> 1
}
/// Returns a mask for the sign bit
fn sign_mask() -> Self::Int;

87
src/int/mod.rs Normal file → Executable file
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@ -19,30 +19,85 @@ pub mod udiv;
pub trait Int {
/// Type with the same width but other signedness
type OtherSign;
/// Unsigned version of Self
type UnsignedInt;
/// Returns the bitwidth of the int type
fn bits() -> u32;
/// Extracts the sign from self and returns a tuple.
///
/// # Examples
///
/// ```rust,ignore
/// let i = -25_i32;
/// let (sign, u) = i.extract_sign();
/// assert_eq!(sign, true);
/// assert_eq!(u, 25_u32);
/// ```
fn extract_sign(self) -> (bool, Self::UnsignedInt);
}
macro_rules! int_impl {
($ity:ty, $sty:ty, $bits:expr) => {
impl Int for $ity {
type OtherSign = $sty;
fn bits() -> u32 {
$bits
}
}
impl Int for $sty {
type OtherSign = $ity;
fn bits() -> u32 {
$bits
}
// TODO: Once i128/u128 support lands, we'll want to add impls for those as well
impl Int for u32 {
type OtherSign = i32;
type UnsignedInt = u32;
fn bits() -> u32 {
32
}
fn extract_sign(self) -> (bool, u32) {
(false, self)
}
}
impl Int for i32 {
type OtherSign = u32;
type UnsignedInt = u32;
fn bits() -> u32 {
32
}
fn extract_sign(self) -> (bool, u32) {
if self < 0 {
(true, !(self as u32) + 1)
} else {
(false, self as u32)
}
}
}
int_impl!(i32, u32, 32);
int_impl!(i64, u64, 64);
int_impl!(i128, u128, 128);
impl Int for u64 {
type OtherSign = i64;
type UnsignedInt = u64;
fn bits() -> u32 {
64
}
fn extract_sign(self) -> (bool, u64) {
(false, self)
}
}
impl Int for i64 {
type OtherSign = u64;
type UnsignedInt = u64;
fn bits() -> u32 {
64
}
fn extract_sign(self) -> (bool, u64) {
if self < 0 {
(true, !(self as u64) + 1)
} else {
(false, self as u64)
}
}
}
/// Trait to convert an integer to/from smaller parts
pub trait LargeInt {