Rollup merge of #76492 - fusion-engineering-forks:int-bits, r=dtolnay
Add associated constant `BITS` to all integer types Recently I've regularly come across this snippet (in a few different crates, including `core` and `std`): ```rust std::mem::size_of<usize>() * 8 ``` I think it's time for a `usize::BITS`.
This commit is contained in:
commit
fef3324043
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@ -14,6 +14,7 @@
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#![feature(generators)]
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#![feature(generator_trait)]
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#![feature(fn_traits)]
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#![feature(int_bits_const)]
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#![feature(min_specialization)]
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#![feature(optin_builtin_traits)]
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#![feature(nll)]
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@ -48,7 +48,7 @@ where
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P: Pointer,
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T: Tag,
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{
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const TAG_BIT_SHIFT: usize = (8 * std::mem::size_of::<usize>()) - T::BITS;
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const TAG_BIT_SHIFT: usize = usize::BITS as usize - T::BITS;
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const ASSERTION: () = {
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assert!(T::BITS <= P::BITS);
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// Used for the transmute_copy's below
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@ -146,7 +146,7 @@
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use core::fmt;
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use core::iter::{FromIterator, FusedIterator, InPlaceIterable, SourceIter, TrustedLen};
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use core::mem::{self, size_of, swap, ManuallyDrop};
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use core::mem::{self, swap, ManuallyDrop};
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use core::ops::{Deref, DerefMut};
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use core::ptr;
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@ -617,7 +617,7 @@ impl<T: Ord> BinaryHeap<T> {
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#[inline(always)]
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fn log2_fast(x: usize) -> usize {
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8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1
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(usize::BITS - x.leading_zeros() - 1) as usize
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}
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// `rebuild` takes O(len1 + len2) operations
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@ -101,6 +101,7 @@
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#![feature(fn_traits)]
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#![feature(fundamental)]
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#![feature(inplace_iteration)]
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#![feature(int_bits_const)]
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#![feature(lang_items)]
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#![feature(layout_for_ptr)]
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#![feature(libc)]
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@ -528,7 +528,7 @@ unsafe impl<#[may_dangle] T, A: AllocRef> Drop for RawVec<T, A> {
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#[inline]
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fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
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if mem::size_of::<usize>() < 8 && alloc_size > isize::MAX as usize {
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if usize::BITS < 64 && alloc_size > isize::MAX as usize {
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Err(CapacityOverflow)
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} else {
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Ok(())
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@ -18,6 +18,7 @@
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#![feature(deque_range)]
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#![feature(inplace_iteration)]
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#![feature(iter_map_while)]
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#![feature(int_bits_const)]
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use std::collections::hash_map::DefaultHasher;
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use std::hash::{Hash, Hasher};
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@ -1,6 +1,5 @@
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use std::borrow::Cow;
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use std::collections::TryReserveError::*;
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use std::mem::size_of;
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use std::ops::Bound::*;
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pub trait IntoCow<'a, B: ?Sized>
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@ -605,7 +604,7 @@ fn test_try_reserve() {
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// on 64-bit, we assume the OS will give an OOM for such a ridiculous size.
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// Any platform that succeeds for these requests is technically broken with
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// ptr::offset because LLVM is the worst.
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let guards_against_isize = size_of::<usize>() < 8;
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let guards_against_isize = usize::BITS < 64;
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{
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// Note: basic stuff is checked by test_reserve
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@ -686,7 +685,7 @@ fn test_try_reserve_exact() {
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const MAX_CAP: usize = isize::MAX as usize;
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const MAX_USIZE: usize = usize::MAX;
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let guards_against_isize = size_of::<usize>() < 8;
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let guards_against_isize = usize::BITS < 64;
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{
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let mut empty_string: String = String::new();
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@ -1341,7 +1341,7 @@ fn test_try_reserve() {
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// on 64-bit, we assume the OS will give an OOM for such a ridiculous size.
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// Any platform that succeeds for these requests is technically broken with
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// ptr::offset because LLVM is the worst.
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let guards_against_isize = size_of::<usize>() < 8;
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let guards_against_isize = usize::BITS < 64;
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{
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// Note: basic stuff is checked by test_reserve
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@ -2086,7 +2086,7 @@ impl<T: ?Sized> Pointer for *const T {
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f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
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if f.width.is_none() {
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f.width = Some(((mem::size_of::<usize>() * 8) / 4) + 2);
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f.width = Some((usize::BITS / 4) as usize + 2);
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}
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}
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f.flags |= 1 << (FlagV1::Alternate as u32);
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@ -20,7 +20,6 @@
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#![macro_use]
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use crate::intrinsics;
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use crate::mem;
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/// Arithmetic operations required by bignums.
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pub trait FullOps: Sized {
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@ -58,25 +57,22 @@ macro_rules! impl_full_ops {
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// This cannot overflow;
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// the output is between `0` and `2^nbits * (2^nbits - 1)`.
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// FIXME: will LLVM optimize this into ADC or similar?
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let nbits = mem::size_of::<$ty>() * 8;
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let v = (self as $bigty) * (other as $bigty) + (carry as $bigty);
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((v >> nbits) as $ty, v as $ty)
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((v >> <$ty>::BITS) as $ty, v as $ty)
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}
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fn full_mul_add(self, other: $ty, other2: $ty, carry: $ty) -> ($ty, $ty) {
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// This cannot overflow;
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// the output is between `0` and `2^nbits * (2^nbits - 1)`.
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let nbits = mem::size_of::<$ty>() * 8;
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let v = (self as $bigty) * (other as $bigty) + (other2 as $bigty) +
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(carry as $bigty);
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((v >> nbits) as $ty, v as $ty)
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((v >> <$ty>::BITS) as $ty, v as $ty)
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}
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fn full_div_rem(self, other: $ty, borrow: $ty) -> ($ty, $ty) {
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debug_assert!(borrow < other);
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// This cannot overflow; the output is between `0` and `other * (2^nbits - 1)`.
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let nbits = mem::size_of::<$ty>() * 8;
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let lhs = ((borrow as $bigty) << nbits) | (self as $bigty);
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let lhs = ((borrow as $bigty) << <$ty>::BITS) | (self as $bigty);
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let rhs = other as $bigty;
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((lhs / rhs) as $ty, (lhs % rhs) as $ty)
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}
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@ -128,13 +124,11 @@ macro_rules! define_bignum {
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/// Makes a bignum from `u64` value.
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pub fn from_u64(mut v: u64) -> $name {
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use crate::mem;
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let mut base = [0; $n];
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let mut sz = 0;
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while v > 0 {
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base[sz] = v as $ty;
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v >>= mem::size_of::<$ty>() * 8;
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v >>= <$ty>::BITS;
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sz += 1;
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}
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$name { size: sz, base: base }
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@ -150,9 +144,7 @@ macro_rules! define_bignum {
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/// Returns the `i`-th bit where bit 0 is the least significant one.
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/// In other words, the bit with weight `2^i`.
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pub fn get_bit(&self, i: usize) -> u8 {
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use crate::mem;
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let digitbits = mem::size_of::<$ty>() * 8;
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let digitbits = <$ty>::BITS as usize;
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let d = i / digitbits;
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let b = i % digitbits;
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((self.base[d] >> b) & 1) as u8
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@ -166,8 +158,6 @@ macro_rules! define_bignum {
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/// Returns the number of bits necessary to represent this value. Note that zero
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/// is considered to need 0 bits.
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pub fn bit_length(&self) -> usize {
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use crate::mem;
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// Skip over the most significant digits which are zero.
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let digits = self.digits();
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let zeros = digits.iter().rev().take_while(|&&x| x == 0).count();
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@ -180,7 +170,7 @@ macro_rules! define_bignum {
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}
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// This could be optimized with leading_zeros() and bit shifts, but that's
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// probably not worth the hassle.
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let digitbits = mem::size_of::<$ty>() * 8;
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let digitbits = <$ty>::BITS as usize;
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let mut i = nonzero.len() * digitbits - 1;
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while self.get_bit(i) == 0 {
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i -= 1;
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@ -265,9 +255,7 @@ macro_rules! define_bignum {
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/// Multiplies itself by `2^bits` and returns its own mutable reference.
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pub fn mul_pow2(&mut self, bits: usize) -> &mut $name {
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use crate::mem;
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let digitbits = mem::size_of::<$ty>() * 8;
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let digitbits = <$ty>::BITS as usize;
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let digits = bits / digitbits;
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let bits = bits % digitbits;
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@ -393,13 +381,11 @@ macro_rules! define_bignum {
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/// Divide self by another bignum, overwriting `q` with the quotient and `r` with the
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/// remainder.
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pub fn div_rem(&self, d: &$name, q: &mut $name, r: &mut $name) {
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use crate::mem;
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// Stupid slow base-2 long division taken from
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// https://en.wikipedia.org/wiki/Division_algorithm
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// FIXME use a greater base ($ty) for the long division.
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assert!(!d.is_zero());
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let digitbits = mem::size_of::<$ty>() * 8;
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let digitbits = <$ty>::BITS as usize;
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for digit in &mut q.base[..] {
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*digit = 0;
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}
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@ -462,10 +448,8 @@ macro_rules! define_bignum {
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impl crate::fmt::Debug for $name {
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fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
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use crate::mem;
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let sz = if self.size < 1 { 1 } else { self.size };
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let digitlen = mem::size_of::<$ty>() * 2;
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let digitlen = <$ty>::BITS as usize / 4;
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write!(f, "{:#x}", self.base[sz - 1])?;
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for &v in self.base[..sz - 1].iter().rev() {
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@ -348,6 +348,20 @@ $EndFeature, "
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pub const MAX: Self = !Self::MIN;
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}
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doc_comment! {
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concat!("The size of this integer type in bits.
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# Examples
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```
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", $Feature, "#![feature(int_bits_const)]
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assert_eq!(", stringify!($SelfT), "::BITS, ", stringify!($BITS), ");",
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$EndFeature, "
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```"),
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#[unstable(feature = "int_bits_const", issue = "76904")]
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pub const BITS: u32 = $BITS;
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}
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doc_comment! {
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concat!("Converts a string slice in a given base to an integer.
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@ -2601,6 +2615,20 @@ $EndFeature, "
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pub const MAX: Self = !0;
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}
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doc_comment! {
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concat!("The size of this integer type in bits.
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# Examples
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```
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", $Feature, "#![feature(int_bits_const)]
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assert_eq!(", stringify!($SelfT), "::BITS, ", stringify!($BITS), ");",
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$EndFeature, "
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```"),
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#[unstable(feature = "int_bits_const", issue = "76904")]
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pub const BITS: u32 = $BITS;
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}
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doc_comment! {
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concat!("Converts a string slice in a given base to an integer.
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@ -565,7 +565,7 @@ fn break_patterns<T>(v: &mut [T]) {
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random
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};
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let mut gen_usize = || {
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if mem::size_of::<usize>() <= 4 {
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if usize::BITS <= 32 {
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gen_u32() as usize
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} else {
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(((gen_u32() as u64) << 32) | (gen_u32() as u64)) as usize
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@ -667,7 +667,7 @@ where
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///
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/// `limit` is the number of allowed imbalanced partitions before switching to `heapsort`. If zero,
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/// this function will immediately switch to heapsort.
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fn recurse<'a, T, F>(mut v: &'a mut [T], is_less: &mut F, mut pred: Option<&'a T>, mut limit: usize)
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fn recurse<'a, T, F>(mut v: &'a mut [T], is_less: &mut F, mut pred: Option<&'a T>, mut limit: u32)
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where
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F: FnMut(&T, &T) -> bool,
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{
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@ -763,7 +763,7 @@ where
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}
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// Limit the number of imbalanced partitions to `floor(log2(len)) + 1`.
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let limit = mem::size_of::<usize>() * 8 - v.len().leading_zeros() as usize;
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let limit = usize::BITS - v.len().leading_zeros();
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recurse(v, &mut is_less, None, limit);
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}
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|
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@ -474,7 +474,7 @@ fn test_iterator_step_by_nth_overflow() {
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}
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let mut it = Test(0);
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let root = usize::MAX >> (::std::mem::size_of::<usize>() * 8 / 2);
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let root = usize::MAX >> (usize::BITS / 2);
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let n = root + 20;
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(&mut it).step_by(n).nth(n);
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assert_eq!(it.0, n as Bigger * n as Bigger);
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@ -52,6 +52,7 @@
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#![feature(partition_point)]
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#![feature(once_cell)]
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#![feature(unsafe_block_in_unsafe_fn)]
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#![feature(int_bits_const)]
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#![deny(unsafe_op_in_unsafe_fn)]
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extern crate test;
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@ -2,7 +2,6 @@ macro_rules! int_module {
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($T:ident, $T_i:ident) => {
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#[cfg(test)]
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mod tests {
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use core::mem;
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use core::ops::{BitAnd, BitOr, BitXor, Not, Shl, Shr};
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use core::$T_i::*;
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@ -82,30 +81,27 @@ macro_rules! int_module {
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#[test]
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fn test_count_zeros() {
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let bits = mem::size_of::<$T>() * 8;
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assert_eq!(A.count_zeros(), bits as u32 - 3);
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assert_eq!(B.count_zeros(), bits as u32 - 2);
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assert_eq!(C.count_zeros(), bits as u32 - 5);
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assert_eq!(A.count_zeros(), $T::BITS - 3);
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assert_eq!(B.count_zeros(), $T::BITS - 2);
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assert_eq!(C.count_zeros(), $T::BITS - 5);
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}
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#[test]
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fn test_leading_trailing_ones() {
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let bits = (mem::size_of::<$T>() * 8) as u32;
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let a: $T = 0b0101_1111;
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assert_eq!(a.trailing_ones(), 5);
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assert_eq!((!a).leading_ones(), bits - 7);
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assert_eq!((!a).leading_ones(), $T::BITS - 7);
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assert_eq!(a.reverse_bits().leading_ones(), 5);
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assert_eq!(_1.leading_ones(), bits);
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assert_eq!(_1.trailing_ones(), bits);
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assert_eq!(_1.leading_ones(), $T::BITS);
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assert_eq!(_1.trailing_ones(), $T::BITS);
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assert_eq!((_1 << 1).trailing_ones(), 0);
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assert_eq!(MAX.leading_ones(), 0);
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assert_eq!((_1 << 1).leading_ones(), bits - 1);
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assert_eq!(MAX.trailing_ones(), bits - 1);
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assert_eq!((_1 << 1).leading_ones(), $T::BITS - 1);
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assert_eq!(MAX.trailing_ones(), $T::BITS - 1);
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assert_eq!(_0.leading_ones(), 0);
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assert_eq!(_0.trailing_ones(), 0);
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|
|
|
@ -4,7 +4,6 @@ macro_rules! uint_module {
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|||
mod tests {
|
||||
use core::ops::{BitAnd, BitOr, BitXor, Not, Shl, Shr};
|
||||
use core::$T_i::*;
|
||||
use std::mem;
|
||||
use std::str::FromStr;
|
||||
|
||||
use crate::num;
|
||||
|
@ -47,30 +46,27 @@ macro_rules! uint_module {
|
|||
|
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#[test]
|
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fn test_count_zeros() {
|
||||
let bits = mem::size_of::<$T>() * 8;
|
||||
assert!(A.count_zeros() == bits as u32 - 3);
|
||||
assert!(B.count_zeros() == bits as u32 - 2);
|
||||
assert!(C.count_zeros() == bits as u32 - 5);
|
||||
assert!(A.count_zeros() == $T::BITS - 3);
|
||||
assert!(B.count_zeros() == $T::BITS - 2);
|
||||
assert!(C.count_zeros() == $T::BITS - 5);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn test_leading_trailing_ones() {
|
||||
let bits = (mem::size_of::<$T>() * 8) as u32;
|
||||
|
||||
let a: $T = 0b0101_1111;
|
||||
assert_eq!(a.trailing_ones(), 5);
|
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assert_eq!((!a).leading_ones(), bits - 7);
|
||||
assert_eq!((!a).leading_ones(), $T::BITS - 7);
|
||||
|
||||
assert_eq!(a.reverse_bits().leading_ones(), 5);
|
||||
|
||||
assert_eq!(_1.leading_ones(), bits);
|
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assert_eq!(_1.trailing_ones(), bits);
|
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assert_eq!(_1.leading_ones(), $T::BITS);
|
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assert_eq!(_1.trailing_ones(), $T::BITS);
|
||||
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assert_eq!((_1 << 1).trailing_ones(), 0);
|
||||
assert_eq!((_1 >> 1).leading_ones(), 0);
|
||||
|
||||
assert_eq!((_1 << 1).leading_ones(), bits - 1);
|
||||
assert_eq!((_1 >> 1).trailing_ones(), bits - 1);
|
||||
assert_eq!((_1 << 1).leading_ones(), $T::BITS - 1);
|
||||
assert_eq!((_1 >> 1).trailing_ones(), $T::BITS - 1);
|
||||
|
||||
assert_eq!(_0.leading_ones(), 0);
|
||||
assert_eq!(_0.trailing_ones(), 0);
|
||||
|
|
|
@ -53,7 +53,7 @@ impl DwarfReader {
|
|||
}
|
||||
|
||||
pub unsafe fn read_sleb128(&mut self) -> i64 {
|
||||
let mut shift: usize = 0;
|
||||
let mut shift: u32 = 0;
|
||||
let mut result: u64 = 0;
|
||||
let mut byte: u8;
|
||||
loop {
|
||||
|
@ -65,7 +65,7 @@ impl DwarfReader {
|
|||
}
|
||||
}
|
||||
// sign-extend
|
||||
if shift < 8 * mem::size_of::<u64>() && (byte & 0x40) != 0 {
|
||||
if shift < u64::BITS && (byte & 0x40) != 0 {
|
||||
result |= (!0 as u64) << shift;
|
||||
}
|
||||
result as i64
|
||||
|
|
|
@ -18,6 +18,7 @@
|
|||
issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
|
||||
)]
|
||||
#![feature(core_intrinsics)]
|
||||
#![feature(int_bits_const)]
|
||||
#![feature(lang_items)]
|
||||
#![feature(libc)]
|
||||
#![feature(nll)]
|
||||
|
|
Loading…
Reference in New Issue