compiler-builtins-zynq/src/int/udiv.rs

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use core::{intrinsics, mem};
use int::{Int, LargeInt};
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/// Returns `n / d`
#[cfg(not(all(feature = "c", target_arch = "arm", not(target_os = "ios"), not(thumbv6m))))]
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#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __udivsi3(n: u32, d: u32) -> u32 {
// Special cases
if d == 0 {
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// NOTE This should be unreachable in safe Rust because the program will panic before
// this intrinsic is called
unsafe {
intrinsics::abort()
}
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}
if n == 0 {
return 0;
}
let mut sr = d.leading_zeros().wrapping_sub(n.leading_zeros());
// d > n
if sr > u32::bits() - 1 {
return 0;
}
// d == 1
if sr == u32::bits() - 1 {
return n;
}
sr += 1;
// 1 <= sr <= u32::bits() - 1
let mut q = n << (u32::bits() - sr);
let mut r = n >> sr;
let mut carry = 0;
for _ in 0..sr {
// r:q = ((r:q) << 1) | carry
r = (r << 1) | (q >> (u32::bits() - 1));
q = (q << 1) | carry;
// carry = 0;
// if r > d {
// r -= d;
// carry = 1;
// }
let s = (d.wrapping_sub(r).wrapping_sub(1)) as i32 >> (u32::bits() - 1);
carry = (s & 1) as u32;
r -= d & s as u32;
}
(q << 1) | carry
}
/// Returns `n % d`
#[cfg(not(all(feature = "c", target_arch = "arm", not(target_os = "ios"))))]
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#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __umodsi3(n: u32, d: u32) -> u32 {
#[cfg(all(feature = "c", target_arch = "arm", not(target_os = "ios")))]
extern "C" {
fn __udivsi3(n: u32, d: u32) -> u32;
}
n - unsafe { __udivsi3(n, d) * d }
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}
/// Returns `n / d` and sets `*rem = n % d`
#[cfg(not(all(feature = "c", target_arch = "arm", not(target_os = "ios"), not(thumbv6m))))]
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#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __udivmodsi4(n: u32, d: u32, rem: Option<&mut u32>) -> u32 {
#[cfg(all(feature = "c", target_arch = "arm", not(target_os = "ios")))]
extern "C" {
fn __udivsi3(n: u32, d: u32) -> u32;
}
let q = unsafe { __udivsi3(n, d) };
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if let Some(rem) = rem {
*rem = n - (q * d);
}
q
}
/// Returns `n / d`
#[cfg_attr(not(test), no_mangle)]
#[cfg(not(all(feature = "c", target_arch = "x86")))]
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pub extern "C" fn __udivdi3(n: u64, d: u64) -> u64 {
__udivmoddi4(n, d, None)
}
/// Returns `n % d`
#[cfg(not(all(feature = "c", target_arch = "x86")))]
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#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __umoddi3(a: u64, b: u64) -> u64 {
let mut rem = unsafe { mem::uninitialized() };
__udivmoddi4(a, b, Some(&mut rem));
rem
}
/// Returns `n / d` and sets `*rem = n % d`
#[cfg_attr(not(test), no_mangle)]
pub extern "C" fn __udivmoddi4(n: u64, d: u64, rem: Option<&mut u64>) -> u64 {
// NOTE X is unknown, K != 0
if n.high() == 0 {
if d.high() == 0 {
// 0 X
// ---
// 0 X
if let Some(rem) = rem {
*rem = u64::from(n.low() % d.low());
}
return u64::from(n.low() / d.low());
} else {
// 0 X
// ---
// K X
if let Some(rem) = rem {
*rem = n;
}
return 0;
};
}
let mut sr;
let mut q;
let mut r;
if d.low() == 0 {
if d.high() == 0 {
// K X
// ---
// 0 0
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// NOTE This should be unreachable in safe Rust because the program will panic before
// this intrinsic is called
unsafe {
intrinsics::abort()
}
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}
if n.low() == 0 {
// K 0
// ---
// K 0
if let Some(rem) = rem {
*rem = u64::from_parts(0, n.high() % d.high());
}
return u64::from(n.high() / d.high());
}
// K K
// ---
// K 0
if d.high().is_power_of_two() {
if let Some(rem) = rem {
*rem = u64::from_parts(n.low(), n.high() & (d.high() - 1));
}
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) = rem {
*rem = n;
}
return 0;
}
sr += 1;
// 1 <= sr <= u32::bits() - 1
q = n << (u64::bits() - sr);
r = n >> sr;
} else {
if d.high() == 0 {
// K X
// ---
// 0 K
if d.low().is_power_of_two() {
if let Some(rem) = rem {
*rem = u64::from(n.low() & (d.low() - 1));
}
if d.low() == 1 {
return n;
} else {
let sr = d.low().trailing_zeros();
return n >> sr;
};
}
sr = 1 + u32::bits() + d.low().leading_zeros() - n.high().leading_zeros();
// 2 <= sr <= u64::bits() - 1
q = n << (u64::bits() - sr);
r = n >> sr;
} else {
// 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) = rem {
*rem = n;
}
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return 0;
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}
sr += 1;
// 1 <= sr <= u32::bits()
q = n << (u64::bits() - sr);
r = n >> sr;
}
}
// Not a special case
// q and r are initialized with
// q = n << (u64::bits() - sr)
// r = n >> sr
// 1 <= sr <= u64::bits() - 1
let mut carry = 0;
for _ in 0..sr {
// r:q = ((r:q) << 1) | carry
r = (r << 1) | (q >> (u64::bits() - 1));
q = (q << 1) | carry as u64;
// carry = 0
// if r >= d {
// r -= d;
// carry = 1;
// }
let s = (d.wrapping_sub(r).wrapping_sub(1)) as i64 >> (u64::bits() - 1);
carry = (s & 1) as u32;
r -= d & s as u64;
}
if let Some(rem) = rem {
*rem = r;
}
(q << 1) | carry as u64
}
#[cfg(test)]
mod tests {
use qc::{U32, U64};
check! {
fn __udivdi3(f: extern fn(u64, u64) -> u64, n: U64, d: U64) -> Option<u64> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
Some(f(n, d))
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}
}
fn __umoddi3(f: extern fn(u64, u64) -> u64, n: U64, d: U64) -> Option<u64> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
Some(f(n, d))
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}
}
fn __udivmoddi4(f: extern fn(u64, u64, Option<&mut u64>) -> u64,
n: U64,
d: U64) -> Option<(u64, u64)> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
let mut r = 0;
let q = f(n, d, Some(&mut r));
Some((q, r))
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}
}
fn __udivsi3(f: extern fn(u32, u32) -> u32, n: U32, d: U32) -> Option<u32> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
Some(f(n, d))
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}
}
fn __umodsi3(f: extern fn(u32, u32) -> u32, n: U32, d: U32) -> Option<u32> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
Some(f(n, d))
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}
}
fn __udivmodsi4(f: extern fn(u32, u32, Option<&mut u32>) -> u32,
n: U32,
d: U32) -> Option<(u32, u32)> {
let (n, d) = (n.0, d.0);
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if d == 0 {
None
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} else {
let mut r = 0;
let q = f(n, d, Some(&mut r));
Some((q, r))
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}
}
}
}