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Change RangeInclusive to a three-field struct.

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Fix #45222.
This commit is contained in:
kennytm 2018-06-19 04:08:20 +08:00
parent 7db82ccd76
commit 0d7e9933d3
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GPG key ID: FEF6C8051D0E013C
5 changed files with 155 additions and 97 deletions
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100
src/libcore/iter/range.rs
View file

@ -10,7 +10,7 @@
use convert::TryFrom;
use mem;
use ops::{self, Add, Sub, Try};
use ops::{self, Add, Sub};
use usize;
use super::{FusedIterator, TrustedLen};
@ -330,23 +330,23 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
#[inline]
fn next(&mut self) -> Option<A> {
if self.start <= self.end {
if self.start < self.end {
let n = self.start.add_one();
Some(mem::replace(&mut self.start, n))
} else {
let last = self.start.replace_one();
self.end.replace_zero();
Some(last)
}
if self.is_empty() {
self.is_iterating = Some(false);
return None;
}
if self.start < self.end {
let n = self.start.add_one();
self.is_iterating = Some(true);
Some(mem::replace(&mut self.start, n))
} else {
None
self.is_iterating = Some(false);
Some(self.start.clone())
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
if !(self.start <= self.end) {
if self.is_empty() {
return (0, Some(0));
}
@ -358,25 +358,29 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
#[inline]
fn nth(&mut self, n: usize) -> Option<A> {
if self.is_empty() {
self.is_iterating = Some(false);
return None;
}
if let Some(plus_n) = self.start.add_usize(n) {
use cmp::Ordering::*;
match plus_n.partial_cmp(&self.end) {
Some(Less) => {
self.is_iterating = Some(true);
self.start = plus_n.add_one();
return Some(plus_n)
}
Some(Equal) => {
self.start.replace_one();
self.end.replace_zero();
self.is_iterating = Some(false);
return Some(plus_n)
}
_ => {}
}
}
self.start.replace_one();
self.end.replace_zero();
self.is_iterating = Some(false);
None
}
@ -394,69 +398,25 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
fn max(mut self) -> Option<A> {
self.next_back()
}
#[inline]
fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
{
let mut accum = init;
if self.start <= self.end {
loop {
let (x, done) =
if self.start < self.end {
let n = self.start.add_one();
(mem::replace(&mut self.start, n), false)
} else {
self.end.replace_zero();
(self.start.replace_one(), true)
};
accum = f(accum, x)?;
if done { break }
}
}
Try::from_ok(accum)
}
}
#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<A: Step> DoubleEndedIterator for ops::RangeInclusive<A> {
#[inline]
fn next_back(&mut self) -> Option<A> {
if self.start <= self.end {
if self.start < self.end {
let n = self.end.sub_one();
Some(mem::replace(&mut self.end, n))
} else {
let last = self.end.replace_zero();
self.start.replace_one();
Some(last)
}
if self.is_empty() {
self.is_iterating = Some(false);
return None;
}
if self.start < self.end {
let n = self.end.sub_one();
self.is_iterating = Some(true);
Some(mem::replace(&mut self.end, n))
} else {
None
self.is_iterating = Some(false);
Some(self.end.clone())
}
}
#[inline]
fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
{
let mut accum = init;
if self.start <= self.end {
loop {
let (x, done) =
if self.start < self.end {
let n = self.end.sub_one();
(mem::replace(&mut self.end, n), false)
} else {
self.start.replace_one();
(self.end.replace_zero(), true)
};
accum = f(accum, x)?;
if done { break }
}
}
Try::from_ok(accum)
}
}
#[stable(feature = "fused", since = "1.26.0")]

38
src/libcore/ops/range.rs
View file

@ -9,6 +9,7 @@
// except according to those terms.
use fmt;
use hash::{Hash, Hasher};
/// An unbounded range (`..`).
///
@ -326,15 +327,37 @@ impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
/// assert_eq!(arr[1..=2], [ 1,2 ]); // RangeInclusive
/// ```
#[doc(alias = "..=")]
#[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186
#[derive(Clone)] // not Copy -- see #27186
#[stable(feature = "inclusive_range", since = "1.26.0")]
pub struct RangeInclusive<Idx> {
// FIXME: The current representation follows RFC 1980,
// but it is known that LLVM is not able to optimize loops following that RFC.
// Consider adding an extra `bool` field to indicate emptiness of the range.
// See #45222 for performance test cases.
pub(crate) start: Idx,
pub(crate) end: Idx,
pub(crate) is_iterating: Option<bool>,
// This field is:
// - `None` when next() or next_back() was never called
// - `Some(true)` when `start <= end` assuming no overflow
// - `Some(false)` otherwise
// The field cannot be a simple `bool` because the `..=` constructor can
// accept non-PartialOrd types, also we want the constructor to be const.
}
#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<Idx: PartialEq> PartialEq for RangeInclusive<Idx> {
#[inline]
fn eq(&self, other: &Self) -> bool {
self.start == other.start && self.end == other.end
}
}
#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<Idx: Eq> Eq for RangeInclusive<Idx> {}
#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<Idx: Hash> Hash for RangeInclusive<Idx> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.start.hash(state);
self.end.hash(state);
}
}
impl<Idx> RangeInclusive<Idx> {
@ -350,7 +373,7 @@ impl<Idx> RangeInclusive<Idx> {
#[stable(feature = "inclusive_range_methods", since = "1.27.0")]
#[inline]
pub const fn new(start: Idx, end: Idx) -> Self {
Self { start, end }
Self { start, end, is_iterating: None }
}
/// Returns the lower bound of the range (inclusive).
@ -492,8 +515,9 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
/// assert!(r.is_empty());
/// ```
#[unstable(feature = "range_is_empty", reason = "recently added", issue = "48111")]
#[inline]
pub fn is_empty(&self) -> bool {
!(self.start <= self.end)
!self.is_iterating.unwrap_or_else(|| self.start <= self.end)
}
}

20
src/libcore/slice/mod.rs
View file

@ -2262,36 +2262,36 @@ impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
if self.end == usize::max_value() { None }
else { (self.start..self.end + 1).get(slice) }
if *self.end() == usize::max_value() { None }
else { (*self.start()..self.end() + 1).get(slice) }
}
#[inline]
fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
if self.end == usize::max_value() { None }
else { (self.start..self.end + 1).get_mut(slice) }
if *self.end() == usize::max_value() { None }
else { (*self.start()..self.end() + 1).get_mut(slice) }
}
#[inline]
unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
(self.start..self.end + 1).get_unchecked(slice)
(*self.start()..self.end() + 1).get_unchecked(slice)
}
#[inline]
unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
(self.start..self.end + 1).get_unchecked_mut(slice)
(*self.start()..self.end() + 1).get_unchecked_mut(slice)
}
#[inline]
fn index(self, slice: &[T]) -> &[T] {
if self.end == usize::max_value() { slice_index_overflow_fail(); }
(self.start..self.end + 1).index(slice)
if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
(*self.start()..self.end() + 1).index(slice)
}
#[inline]
fn index_mut(self, slice: &mut [T]) -> &mut [T] {
if self.end == usize::max_value() { slice_index_overflow_fail(); }
(self.start..self.end + 1).index_mut(slice)
if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
(*self.start()..self.end() + 1).index_mut(slice)
}
}

20
src/libcore/str/mod.rs
View file

@ -2004,31 +2004,31 @@ mod traits {
type Output = str;
#[inline]
fn get(self, slice: &str) -> Option<&Self::Output> {
if self.end == usize::max_value() { None }
else { (self.start..self.end+1).get(slice) }
if *self.end() == usize::max_value() { None }
else { (*self.start()..self.end()+1).get(slice) }
}
#[inline]
fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> {
if self.end == usize::max_value() { None }
else { (self.start..self.end+1).get_mut(slice) }
if *self.end() == usize::max_value() { None }
else { (*self.start()..self.end()+1).get_mut(slice) }
}
#[inline]
unsafe fn get_unchecked(self, slice: &str) -> &Self::Output {
(self.start..self.end+1).get_unchecked(slice)
(*self.start()..self.end()+1).get_unchecked(slice)
}
#[inline]
unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output {
(self.start..self.end+1).get_unchecked_mut(slice)
(*self.start()..self.end()+1).get_unchecked_mut(slice)
}
#[inline]
fn index(self, slice: &str) -> &Self::Output {
if self.end == usize::max_value() { str_index_overflow_fail(); }
(self.start..self.end+1).index(slice)
if *self.end() == usize::max_value() { str_index_overflow_fail(); }
(*self.start()..self.end()+1).index(slice)
}
#[inline]
fn index_mut(self, slice: &mut str) -> &mut Self::Output {
if self.end == usize::max_value() { str_index_overflow_fail(); }
(self.start..self.end+1).index_mut(slice)
if *self.end() == usize::max_value() { str_index_overflow_fail(); }
(*self.start()..self.end()+1).index_mut(slice)
}
}

74
src/test/codegen/issue-45222.rs Normal file
View file

@ -0,0 +1,74 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -O
// min-llvm-version 6.0
#![crate_type = "lib"]
// verify that LLVM recognizes a loop involving 0..=n and will const-fold it.
//------------------------------------------------------------------------------
// Example from original issue #45222
fn foo2(n: u64) -> u64 {
let mut count = 0;
for _ in 0..n {
for j in (0..=n).rev() {
count += j;
}
}
count
}
// CHECK-LABEL: @check_foo2
#[no_mangle]
pub fn check_foo2() -> u64 {
// CHECK: ret i64 500005000000000
foo2(100000)
}
//------------------------------------------------------------------------------
// Simplified example of #45222
fn triangle_inc(n: u64) -> u64 {
let mut count = 0;
for j in 0 ..= n {
count += j;
}
count
}
// CHECK-LABEL: @check_triangle_inc
#[no_mangle]
pub fn check_triangle_inc() -> u64 {
// CHECK: ret i64 5000050000
triangle_inc(100000)
}
//------------------------------------------------------------------------------
// Demo in #48012
fn foo3r(n: u64) -> u64 {
let mut count = 0;
(0..n).for_each(|_| {
(0 ..= n).rev().for_each(|j| {
count += j;
})
});
count
}
// CHECK-LABEL: @check_foo3r
#[no_mangle]
pub fn check_foo3r() -> u64 {
// CHECK: ret i64 500005000000000
foo3r(100000)
}