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Remove manual unrolling from slice::Iter(Mut)::try_fold #64600

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merged 2 commits into from
Sep 30, 2019
Merged

Remove manual unrolling from slice::Iter(Mut)::try_fold #64600

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92e91f7
Remove manual unrolling from slice::Iter(Mut)::try_fold
scottmcm Sep 19, 2019
6ac64ab
Just delete the overrides now that they match the default implementat…
scottmcm Sep 23, 2019
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69 changes: 1 addition & 68 deletions src/libcore/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ use crate::fmt;
use crate::intrinsics::{assume, exact_div, unchecked_sub, is_aligned_and_not_null};
use crate::isize;
use crate::iter::*;
use crate::ops::{FnMut, Try, self};
use crate::ops::{FnMut, self};
use crate::option::Option;
use crate::option::Option::{None, Some};
use crate::result::Result;
Expand Down Expand Up @@ -3180,39 +3180,6 @@ macro_rules! iterator {
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>
{
// manual unrolling is needed when there are conditional exits from the loop
let mut accum = init;
unsafe {
while len!(self) >= 4 {
accum = f(accum, next_unchecked!(self))?;
accum = f(accum, next_unchecked!(self))?;
accum = f(accum, next_unchecked!(self))?;
accum = f(accum, next_unchecked!(self))?;
}
while !is_empty!(self) {
accum = f(accum, next_unchecked!(self))?;
}
}
Try::from_ok(accum)
}

#[inline]
fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
// Let LLVM unroll this, rather than using the default
// impl that would force the manual unrolling above
let mut accum = init;
while let Some(x) = self.next() {
accum = f(accum, x);
}
accum
}

#[inline]
#[rustc_inherit_overflow_checks]
fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
Expand Down Expand Up @@ -3283,40 +3250,6 @@ macro_rules! iterator {
Some(next_back_unchecked!(self))
}
}

#[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>
{
// manual unrolling is needed when there are conditional exits from the loop
let mut accum = init;
unsafe {
while len!(self) >= 4 {
accum = f(accum, next_back_unchecked!(self))?;
accum = f(accum, next_back_unchecked!(self))?;
accum = f(accum, next_back_unchecked!(self))?;
accum = f(accum, next_back_unchecked!(self))?;
}
// inlining is_empty everywhere makes a huge performance difference
while !is_empty!(self) {
accum = f(accum, next_back_unchecked!(self))?;
}
}
Try::from_ok(accum)
}

#[inline]
fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
// Let LLVM unroll this, rather than using the default
// impl that would force the manual unrolling above
let mut accum = init;
while let Some(x) = self.next_back() {
accum = f(accum, x);
}
accum
}
}

#[stable(feature = "fused", since = "1.26.0")]
Expand Down