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port udivmoddi4 and __aeabi_uldivmod

This commit is contained in:
Jorge Aparicio 2016-08-10 19:12:37 -05:00
parent c4142ed777
commit 950564607d
4 changed files with 299 additions and 1 deletions
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3
Cargo.toml
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@ -2,3 +2,6 @@
authors = ["Jorge Aparicio <japaricious@gmail.com>"]
name = "rustc_builtins"
version = "0.1.0"
[dev-dependencies]
quickcheck = "0.3.1"

17
src/arm.rs
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@ -1,3 +1,20 @@
use core::mem;
#[repr(C)]
pub struct u64x2 {
a: u64,
b: u64,
}
#[no_mangle]
pub unsafe extern "aapcs" fn __aeabi_uldivmod(num: u64, den: u64) -> u64x2 {
let mut rem = mem::uninitialized();
let quot = ::__udivmoddi4(num, den, &mut rem);
u64x2 { a: quot, b: rem }
}
extern "C" {
fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;
fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8;

259
src/lib.rs
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@ -8,6 +8,9 @@
#[cfg(test)]
extern crate core;
#[cfg(test)]
#[macro_use]
extern crate quickcheck;
#[cfg(target_arch = "arm")]
pub mod arm;
@ -15,6 +18,8 @@ pub mod arm;
#[cfg(test)]
mod test;
use core::mem;
/// Trait for some basic operations on integers
trait Int {
fn bits() -> usize;
@ -93,3 +98,257 @@ absv_i2!(__absvsi2: i32);
absv_i2!(__absvdi2: i64);
// TODO(rust-lang/35118)?
// absv_i2!(__absvti2, i128);
#[no_mangle]
pub extern "C" fn __udivmoddi4(a: u64, b: u64, rem: *mut u64) -> u64 {
#[cfg(target_endian = "little")]
#[repr(C)]
#[derive(Debug)]
struct words {
low: u32,
high: u32,
}
#[cfg(target_endian = "big")]
#[repr(C)]
#[derive(Debug)]
struct words {
high: u32,
low: u32,
}
impl words {
fn all(&mut self) -> &mut u64 {
unsafe { mem::transmute(self) }
}
fn u64(&self) -> u64 {
unsafe { *(self as *const _ as *const u64) }
}
}
impl From<u64> for words {
fn from(x: u64) -> words {
unsafe { mem::transmute(x) }
}
}
let u32_bits = u32::bits() as u32;
let u64_bits = u64::bits() as u32;
let n = words::from(a);
let d = words::from(b);
// NOTE X is unknown, K != 0
if n.high == 0 {
return if d.high == 0 {
// 0 X
// ---
// 0 X
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = u64::from(n.low % d.low);
}
u64::from(n.low / d.low)
} else
// d.high != 0
{
// 0 X
// ---
// K X
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = u64::from(n.low);
}
0
};
}
let mut sr;
// NOTE IMO it should be possible to leave these "uninitialized" (just declare them here)
// because these variables get initialized below, but if I do that the compiler complains about
// them being used before being initialized.
let mut q = words { low: 0, high: 0 };
let mut r = words { low: 0, high: 0 };
// n.high != 0
if d.low == 0 {
if d.high == 0 {
// K X
// ---
// 0 0
// NOTE copied verbatim from compiler-rt, but does division by zero even make sense?
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = u64::from(n.high % d.low);
}
return u64::from(n.high / d.low);
}
// d.high != 0
if n.low == 0 {
// K 0
// ---
// K 0
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = words {
low: 0,
high: n.high % d.high,
}
.u64();
}
return u64::from(n.high / d.high);
}
// n.low != 0
// K K
// ---
// K 0
if d.high.is_power_of_two() {
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = words {
low: n.low,
high: n.high & (d.high - 1),
}
.u64()
}
return u64::from(n.high >> d.high.trailing_zeros());
}
sr = d.high.leading_zeros().wrapping_sub(n.high.leading_zeros());
// D > N
if sr > u32_bits - 2 {
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = n.u64();
}
return 0;
}
sr = sr + 1;
// 1 <= sr <= u32_bits - 1
// *q.all() = n.u64() << (u64_bits - sr);
q.low = 0;
q.high = n.low << (u32_bits - sr);
// *r.all() = n.u64() >> sr
r.high = n.high >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr);
} else
// d.low != 0
{
if d.high == 0 {
// K X
// ---
// 0 K
if d.low.is_power_of_two() {
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = u64::from(n.low & (d.low - 1));
}
return if d.low == 1 {
n.u64()
} else {
let sr = d.low.trailing_zeros();
words {
low: (n.high << (u32_bits - sr)) | (n.low >> sr),
high: n.high >> sr,
}
.u64()
};
}
sr = 1 + u32_bits + d.low.leading_zeros() - n.high.leading_zeros();
// 2 <= sr <= u64_bits - 1
// *q.all() = n.u64() << (u64_bits - sr)
// *r.all() = n.u64() >> sr;
if sr == u32_bits {
q.low = 0;
q.high = n.low;
r.high = 0;
r.low = n.high;
} else if sr < u32_bits
// 2 <= sr <= u32_bits - 1
{
q.low = 0;
q.high = n.low << (u32_bits - sr);
r.high = n.high >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr);
} else
// u32_bits + 1 <= sr <= u64_bits - 1
{
q.low = n.low << (u64_bits - sr);
q.high = (n.high << (u64_bits - sr)) | (n.low >> (sr - u32_bits));
r.high = 0;
r.low = n.high >> (sr - u32_bits);
}
} else
// d.high != 0
{
// K X
// ---
// K K
sr = d.high.leading_zeros().wrapping_sub(n.high.leading_zeros());
// D > N
if sr > u32_bits - 1 {
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = a;
return 0;
}
}
sr += 1;
// 1 <= sr <= u32_bits
// *q.all() = n.u64() << (u64_bits - sr)
q.low = 0;
if sr == u32_bits {
q.high = n.low;
r.high = 0;
r.low = n.high;
} else {
q.high = n.low << (u32_bits - sr);
r.high = n.high >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr);
}
}
}
// Not a special case
// q and r are initialized with
// *q.all() = n.u64() << (u64_bits - sr)
// *.r.all() = n.u64() >> sr
// 1 <= sr <= u64_bits - 1
let mut carry = 0;
for _ in 0..sr {
// r:q = ((r:q) << 1) | carry
r.high = (r.high << 1) | (r.low >> (u32_bits - 1));
r.low = (r.low << 1) | (q.high >> (u32_bits - 1));
q.high = (q.high << 1) | (q.low >> (u32_bits - 1));
q.low = (q.low << 1) | carry;
// carry = 0
// if r.u64() >= d.u64() {
// *r.all() -= d.u64();
// carry = 1;
// }
let s = (d.u64().wrapping_sub(r.u64()).wrapping_sub(1)) as i64 >> (u64_bits - 1);
carry = (s & 1) as u32;
*r.all() -= d.u64() & s as u64;
}
*q.all() = (q.u64() << 1) | carry as u64;
if let Some(rem) = unsafe { rem.as_mut() } {
*rem = r.u64();
}
q.u64()
}

21
src/test.rs
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@ -1,4 +1,6 @@
use std::panic;
use std::{mem, panic};
use quickcheck::TestResult;
macro_rules! absv_i2 {
($intrinsic:ident: $ty:ident) => {
@ -23,3 +25,20 @@ absv_i2!(__absvsi2: i32);
absv_i2!(__absvdi2: i64);
// TODO(rust-lang/35118)?
// absv_i2!(__absvti2: i128);
quickcheck! {
fn udivmoddi4(a: (u32, u32), b: (u32, u32)) -> TestResult {
let (a, b) = unsafe {
(mem::transmute(a), mem::transmute(b))
};
if b == 0 {
TestResult::discard()
} else {
let mut r = 0;
let q = ::__udivmoddi4(a, b, &mut r);
TestResult::from_bool(q * b + r == a)
}
}
}