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Rollup merge of #72166 - nnethercote:simpler-slice-Iterator-methods, r=cuviper

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Simpler slice `Iterator` methods

These reduce the amount of LLVM IR generated, helping compile times.

r? @cuviper
This commit is contained in:
Dylan DPC 2020-05-16 12:43:01 +02:00 committed by GitHub
commit e8f0fb1f13
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2 changed files with 106 additions and 18 deletions
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2
src/libcore/iter/traits/iterator.rs
View File

@ -333,7 +333,7 @@ pub trait Iterator {
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
for x in self {
while let Some(x) = self.next() {
if n == 0 {
return Some(x);
}

122
src/libcore/slice/mod.rs
View File

@ -3179,6 +3179,7 @@ macro_rules! is_empty {
$self.ptr.as_ptr() as *const T == $self.end
};
}
// To get rid of some bounds checks (see `position`), we compute the length in a somewhat
// unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
macro_rules! len {
@ -3347,40 +3348,127 @@ macro_rules! iterator {
self.next_back()
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile.
#[inline]
fn for_each<F>(mut self, mut f: F)
where
Self: Sized,
F: FnMut(Self::Item),
{
while let Some(x) = self.next() {
f(x);
}
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile.
#[inline]
fn all<F>(&mut self, mut f: F) -> bool
where
Self: Sized,
F: FnMut(Self::Item) -> bool,
{
while let Some(x) = self.next() {
if !f(x) {
return false;
}
}
true
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile.
#[inline]
fn any<F>(&mut self, mut f: F) -> bool
where
Self: Sized,
F: FnMut(Self::Item) -> bool,
{
while let Some(x) = self.next() {
if f(x) {
return true;
}
}
false
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile.
#[inline]
fn find<P>(&mut self, mut predicate: P) -> Option<Self::Item>
where
Self: Sized,
P: FnMut(&Self::Item) -> bool,
{
while let Some(x) = self.next() {
if predicate(&x) {
return Some(x);
}
}
None
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile.
#[inline]
fn find_map<B, F>(&mut self, mut f: F) -> Option<B>
where
Self: Sized,
F: FnMut(Self::Item) -> Option<B>,
{
while let Some(x) = self.next() {
if let Some(y) = f(x) {
return Some(y);
}
}
None
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile. Also, the `assume` avoids a bounds check.
#[inline]
#[rustc_inherit_overflow_checks]
fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
Self: Sized,
P: FnMut(Self::Item) -> bool,
{
// The addition might panic on overflow.
let n = len!(self);
self.try_fold(0, move |i, x| {
if predicate(x) { Err(i) }
else { Ok(i + 1) }
}).err()
.map(|i| {
let mut i = 0;
while let Some(x) = self.next() {
if predicate(x) {
unsafe { assume(i < n) };
i
})
return Some(i);
}
i += 1;
}
None
}
// We override the default implementation, which uses `try_fold`,
// because this simple implementation generates less LLVM IR and is
// faster to compile. Also, the `assume` avoids a bounds check.
#[inline]
fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: Sized + ExactSizeIterator + DoubleEndedIterator
{
// No need for an overflow check here, because `ExactSizeIterator`
let n = len!(self);
self.try_rfold(n, move |i, x| {
let i = i - 1;
if predicate(x) { Err(i) }
else { Ok(i) }
}).err()
.map(|i| {
let mut i = n;
while let Some(x) = self.next_back() {
i -= 1;
if predicate(x) {
unsafe { assume(i < n) };
i
})
return Some(i);
}
}
None
}
$($extra)*