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refactor: use Int traits, words -> U64, fmt

This commit is contained in:
Jorge Aparicio 2016-08-11 01:15:51 -05:00
parent d6be95a3bb
commit a84579d3c1
1 changed files with 108 additions and 110 deletions
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212
src/lib.rs
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@ -18,8 +18,6 @@ pub mod arm;
#[cfg(test)] #[cfg(test)]
mod test; mod test;
use core::mem;
/// Trait for some basic operations on integers /// Trait for some basic operations on integers
trait Int { trait Int {
fn bits() -> usize; fn bits() -> usize;
@ -27,16 +25,24 @@ trait Int {
// TODO: Once i128/u128 support lands, we'll want to add impls for those as well // TODO: Once i128/u128 support lands, we'll want to add impls for those as well
impl Int for u32 { impl Int for u32 {
fn bits() -> usize { 32 } fn bits() -> usize {
32
}
} }
impl Int for i32 { impl Int for i32 {
fn bits() -> usize { 32 } fn bits() -> usize {
32
}
} }
impl Int for u64 { impl Int for u64 {
fn bits() -> usize { 64 } fn bits() -> usize {
64
}
} }
impl Int for i64 { impl Int for i64 {
fn bits() -> usize { 64 } fn bits() -> usize {
64
}
} }
/// Trait to convert an integer to/from smaller parts /// Trait to convert an integer to/from smaller parts
@ -99,131 +105,124 @@ absv_i2!(__absvdi2: i64);
// TODO(rust-lang/35118)? // TODO(rust-lang/35118)?
// absv_i2!(__absvti2, i128); // absv_i2!(__absvti2, i128);
/// Return `n / d` and `*rem = n % d`
#[no_mangle] #[no_mangle]
pub extern "C" fn __udivmoddi4(a: u64, b: u64, rem: Option<&mut u64>) -> u64 { pub extern "C" fn __udivmoddi4(n: u64, d: u64, rem: Option<&mut u64>) -> u64 {
use core::ops::{Index, IndexMut, RangeFull};
#[cfg(target_endian = "little")] #[cfg(target_endian = "little")]
#[repr(C)] #[repr(C)]
#[derive(Debug)] struct U64 {
struct words {
low: u32, low: u32,
high: u32, high: u32,
} }
#[cfg(target_endian = "big")] #[cfg(target_endian = "big")]
#[repr(C)] #[repr(C)]
#[derive(Debug)] struct U64 {
struct words {
high: u32, high: u32,
low: u32, low: u32,
} }
impl words { impl Index<RangeFull> for U64 {
fn all(&mut self) -> &mut u64 { type Output = u64;
unsafe { mem::transmute(self) }
}
fn u64(&self) -> u64 { fn index(&self, _: RangeFull) -> &u64 {
unsafe { *(self as *const _ as *const u64) } unsafe { &*(self as *const _ as *const u64) }
} }
} }
impl From<u64> for words { impl IndexMut<RangeFull> for U64 {
fn from(x: u64) -> words { fn index_mut(&mut self, _: RangeFull) -> &mut u64 {
unsafe { mem::transmute(x) } unsafe { &mut *(self as *const _ as *mut u64) }
} }
} }
let u32_bits = u32::bits() as u32; let u32_bits = u32::bits() as u32;
let u64_bits = u64::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 // NOTE X is unknown, K != 0
if n.high == 0 { if n.high() == 0 {
if d.high == 0 { if d.high() == 0 {
// 0 X // 0 X
// --- // ---
// 0 X // 0 X
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = u64::from(n.low % d.low); *rem = u64::from(n.low() % d.low());
} }
return u64::from(n.low / d.low); return u64::from(n.low() / d.low());
} else } else
// d.high != 0 // d.high() != 0
{ {
// 0 X // 0 X
// --- // ---
// K X // K X
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = u64::from(n.low); *rem = u64::from(n.low());
} }
return 0; return 0;
}; };
} }
let mut sr; let mut sr;
// NOTE IMO it should be possible to leave these "uninitialized" (just declare them here) let mut q = U64 { low: 0, high: 0 };
// because these variables get initialized below, but if I do that the compiler complains about let mut r = U64 { low: 0, high: 0 };
// 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 // n.high() != 0
if d.low == 0 { if d.low() == 0 {
if d.high == 0 { if d.high() == 0 {
// K X // K X
// --- // ---
// 0 0 // 0 0
// NOTE copied verbatim from compiler-rt, but does division by zero even make sense? // NOTE copied verbatim from compiler-rt. This probably lets the intrinsic decide how to
// handle the division by zero (SIGFPE, 0, etc.). But this part shouldn't be reachable
// from safe code.
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = u64::from(n.high % d.low); *rem = u64::from(n.high() % d.low());
} }
return u64::from(n.high / d.low); return u64::from(n.high() / d.low());
} }
// d.high != 0 // d.high() != 0
if n.low == 0 { if n.low() == 0 {
// K 0 // K 0
// --- // ---
// K 0 // K 0
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = words { *rem = U64 {
low: 0, low: 0,
high: n.high % d.high, high: n.high() % d.high(),
}[..];
} }
.u64(); return u64::from(n.high() / d.high());
}
return u64::from(n.high / d.high);
} }
// n.low != 0 // n.low() != 0
// K K // K K
// --- // ---
// K 0 // K 0
if d.high.is_power_of_two() { if d.high().is_power_of_two() {
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = words { *rem = U64 {
low: n.low, low: n.low(),
high: n.high & (d.high - 1), high: n.high() & (d.high() - 1),
} }[..];
.u64()
} }
return u64::from(n.high >> d.high.trailing_zeros()); return u64::from(n.high() >> d.high().trailing_zeros());
} }
sr = d.high.leading_zeros().wrapping_sub(n.high.leading_zeros()); sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
// D > N // D > N
if sr > u32_bits - 2 { if sr > u32_bits - 2 {
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = n.u64(); *rem = n;
} }
return 0; return 0;
} }
@ -231,75 +230,74 @@ pub extern "C" fn __udivmoddi4(a: u64, b: u64, rem: Option<&mut u64>) -> u64 {
sr = sr + 1; sr = sr + 1;
// 1 <= sr <= u32_bits - 1 // 1 <= sr <= u32_bits - 1
// *q.all() = n.u64() << (u64_bits - sr); // q = n << (u64_bits - sr);
q.low = 0; q.low = 0;
q.high = n.low << (u32_bits - sr); q.high = n.low() << (u32_bits - sr);
// *r.all() = n.u64() >> sr // r = n >> sr
r.high = n.high >> sr; r.high = n.high() >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr); r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
} else } else
// d.low != 0 // d.low() != 0
{ {
if d.high == 0 { if d.high() == 0 {
// K X // K X
// --- // ---
// 0 K // 0 K
if d.low.is_power_of_two() { if d.low().is_power_of_two() {
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = u64::from(n.low & (d.low - 1)); *rem = u64::from(n.low() & (d.low() - 1));
} }
return if d.low == 1 { if d.low() == 1 {
n.u64() return n;
} else { } else {
let sr = d.low.trailing_zeros(); let sr = d.low().trailing_zeros();
words { return U64 {
low: (n.high << (u32_bits - sr)) | (n.low >> sr), low: (n.high() << (u32_bits - sr)) | (n.low() >> sr),
high: n.high >> sr, high: n.high() >> sr,
} }[..];
.u64()
}; };
} }
sr = 1 + u32_bits + d.low.leading_zeros() - n.high.leading_zeros(); sr = 1 + u32_bits + d.low().leading_zeros() - n.high().leading_zeros();
// 2 <= sr <= u64_bits - 1 // 2 <= sr <= u64_bits - 1
// *q.all() = n.u64() << (u64_bits - sr) // q = n << (u64_bits - sr)
// *r.all() = n.u64() >> sr; // r = n >> sr;
if sr == u32_bits { if sr == u32_bits {
q.low = 0; q.low = 0;
q.high = n.low; q.high = n.low();
r.high = 0; r.high = 0;
r.low = n.high; r.low = n.high();
} else if sr < u32_bits } else if sr < u32_bits
// 2 <= sr <= u32_bits - 1 // 2 <= sr <= u32_bits - 1
{ {
q.low = 0; q.low = 0;
q.high = n.low << (u32_bits - sr); q.high = n.low() << (u32_bits - sr);
r.high = n.high >> sr; r.high = n.high() >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr); r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
} else } else
// u32_bits + 1 <= sr <= u64_bits - 1 // u32_bits + 1 <= sr <= u64_bits - 1
{ {
q.low = n.low << (u64_bits - sr); q.low = n.low() << (u64_bits - sr);
q.high = (n.high << (u64_bits - sr)) | (n.low >> (sr - u32_bits)); q.high = (n.high() << (u64_bits - sr)) | (n.low() >> (sr - u32_bits));
r.high = 0; r.high = 0;
r.low = n.high >> (sr - u32_bits); r.low = n.high() >> (sr - u32_bits);
} }
} else } else
// d.high != 0 // d.high() != 0
{ {
// K X // K X
// --- // ---
// K K // K K
sr = d.high.leading_zeros().wrapping_sub(n.high.leading_zeros()); sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
// D > N // D > N
if sr > u32_bits - 1 { if sr > u32_bits - 1 {
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = a; *rem = n;
return 0; return 0;
} }
} }
@ -307,52 +305,51 @@ pub extern "C" fn __udivmoddi4(a: u64, b: u64, rem: Option<&mut u64>) -> u64 {
sr += 1; sr += 1;
// 1 <= sr <= u32_bits // 1 <= sr <= u32_bits
// *q.all() = n.u64() << (u64_bits - sr) // q = n << (u64_bits - sr)
q.low = 0; q.low = 0;
if sr == u32_bits { if sr == u32_bits {
q.high = n.low; q.high = n.low();
r.high = 0; r.high = 0;
r.low = n.high; r.low = n.high();
} else { } else {
q.high = n.low << (u32_bits - sr); q.high = n.low() << (u32_bits - sr);
r.high = n.high >> sr; r.high = n.high() >> sr;
r.low = (n.high << (u32_bits - sr)) | (n.low >> sr); r.low = (n.high() << (u32_bits - sr)) | (n.low() >> sr);
} }
} }
} }
// Not a special case // Not a special case
// q and r are initialized with // q and r are initialized with
// *q.all() = n.u64() << (u64_bits - sr) // q = n << (u64_bits - sr)
// *.r.all() = n.u64() >> sr // r = n >> sr
// 1 <= sr <= u64_bits - 1 // 1 <= sr <= u64_bits - 1
let mut carry = 0; let mut carry = 0;
for _ in 0..sr { for _ in 0..sr {
// r:q = ((r:q) << 1) | carry // r:q = ((r:q) << 1) | carry
r.high = (r.high << 1) | (r.low >> (u32_bits - 1)); r[..] = (r[..] << 1) | (q[..] >> 63);
r.low = (r.low << 1) | (q.high >> (u32_bits - 1)); q[..] = (q[..] << 1) | carry as u64;
q.high = (q.high << 1) | (q.low >> (u32_bits - 1));
q.low = (q.low << 1) | carry;
// carry = 0 // carry = 0
// if r.u64() >= d.u64() { // if r >= d {
// *r.all() -= d.u64(); // r -= d;
// carry = 1; // carry = 1;
// } // }
let s = (d.u64().wrapping_sub(r.u64()).wrapping_sub(1)) as i64 >> (u64_bits - 1); let s = (d.wrapping_sub(r[..]).wrapping_sub(1)) as i64 >> (u64_bits - 1);
carry = (s & 1) as u32; carry = (s & 1) as u32;
*r.all() -= d.u64() & s as u64; r[..] -= d & s as u64;
} }
*q.all() = (q.u64() << 1) | carry as u64; q[..] = (q[..] << 1) | carry as u64;
if let Some(rem) = rem { if let Some(rem) = rem {
*rem = r.u64(); *rem = r[..];
} }
q.u64() q[..]
} }
/// Return `n / d` and `*rem = n % d`
#[no_mangle] #[no_mangle]
pub extern "C" fn __udivmodsi4(a: u32, b: u32, rem: Option<&mut u32>) -> u32 { pub extern "C" fn __udivmodsi4(a: u32, b: u32, rem: Option<&mut u32>) -> u32 {
let d = __udivsi3(a, b); let d = __udivsi3(a, b);
@ -362,6 +359,7 @@ pub extern "C" fn __udivmodsi4(a: u32, b: u32, rem: Option<&mut u32>) -> u32 {
return d; return d;
} }
/// Return `n / d`
#[no_mangle] #[no_mangle]
pub extern "C" fn __udivsi3(n: u32, d: u32) -> u32 { pub extern "C" fn __udivsi3(n: u32, d: u32) -> u32 {
let u32_bits = u32::bits() as u32; let u32_bits = u32::bits() as u32;