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By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec. All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,61 +1,35 @@ | ||
| use core::ptr; | ||
| use core::iter; | ||
|
|
||
| use crate::alloc::Allocator; | ||
| use crate::raw_vec::RawVec; | ||
|
|
||
| use super::{ExtendElement, IsZero, Vec}; | ||
| use super::{IsZero, Vec}; | ||
|
|
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| // Specialization trait used for Vec::from_elem | ||
| pub(super) trait SpecFromElem: Sized { | ||
| fn from_elem<A: Allocator>(elem: Self, n: usize, alloc: A) -> Vec<Self, A>; | ||
| } | ||
|
|
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| #[inline] | ||
| fn basic_from_elem<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> { | ||
| let mut v = Vec::with_capacity_in(n, alloc); | ||
| v.extend(iter::repeat_n(elem, n)); | ||
| v | ||
| } | ||
|
|
||
| impl<T: Clone> SpecFromElem for T { | ||
| #[inline] | ||
| default fn from_elem<A: Allocator>(elem: Self, n: usize, alloc: A) -> Vec<Self, A> { | ||
| let mut v = Vec::with_capacity_in(n, alloc); | ||
| v.extend_with(n, ExtendElement(elem)); | ||
| v | ||
| basic_from_elem(elem, n, alloc) | ||
| } | ||
| } | ||
|
|
||
| impl<T: Clone + IsZero> SpecFromElem for T { | ||
| #[inline] | ||
| default fn from_elem<A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> { | ||
| fn from_elem<A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> { | ||
| if elem.is_zero() { | ||
| return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n }; | ||
| } | ||
| let mut v = Vec::with_capacity_in(n, alloc); | ||
| v.extend_with(n, ExtendElement(elem)); | ||
| v | ||
| } | ||
| } | ||
|
|
||
| impl SpecFromElem for i8 { | ||
| #[inline] | ||
| fn from_elem<A: Allocator>(elem: i8, n: usize, alloc: A) -> Vec<i8, A> { | ||
| if elem == 0 { | ||
| return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n }; | ||
| } | ||
| unsafe { | ||
| let mut v = Vec::with_capacity_in(n, alloc); | ||
| ptr::write_bytes(v.as_mut_ptr(), elem as u8, n); | ||
| v.set_len(n); | ||
| v | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl SpecFromElem for u8 { | ||
| #[inline] | ||
| fn from_elem<A: Allocator>(elem: u8, n: usize, alloc: A) -> Vec<u8, A> { | ||
| if elem == 0 { | ||
| return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n }; | ||
| } | ||
| unsafe { | ||
| let mut v = Vec::with_capacity_in(n, alloc); | ||
| ptr::write_bytes(v.as_mut_ptr(), elem, n); | ||
| v.set_len(n); | ||
| v | ||
| } | ||
| basic_from_elem(elem, n, alloc) | ||
| } | ||
| } |
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