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Auto merge of #106275 - Nilstrieb:const-eval-select-me-some-compile-time, r=thomcc

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Use some more `const_eval_select` in pointer methods for compile times

Builds on top of #105435

`is_aligned_to` is _huge_ with calling `align_offset`, so this should cut it down a lot.

This shows up in https://github.com/rust-lang/rust/issues/65031#issuecomment-1367574340
This commit is contained in:
bors 2022-12-31 17:19:10 +00:00
commit dd01a163c1
2 changed files with 66 additions and 22 deletions
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44
library/core/src/ptr/const_ptr.rs
View File

@ -1,6 +1,6 @@
use super::*;
use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::intrinsics;
use crate::intrinsics::{self, const_eval_select};
use crate::mem;
use crate::slice::{self, SliceIndex};
@ -34,12 +34,23 @@ impl<T: ?Sized> *const T {
#[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
#[inline]
pub const fn is_null(self) -> bool {
// Compare via a cast to a thin pointer, so fat pointers are only
// considering their "data" part for null-ness.
match (self as *const u8).guaranteed_eq(null()) {
None => false,
Some(res) => res,
#[inline]
fn runtime_impl(ptr: *const u8) -> bool {
ptr.addr() == 0
}
#[inline]
const fn const_impl(ptr: *const u8) -> bool {
// Compare via a cast to a thin pointer, so fat pointers are only
// considering their "data" part for null-ness.
match (ptr).guaranteed_eq(null_mut()) {
None => false,
Some(res) => res,
}
}
// SAFETY: The two versions are equivalent at runtime.
unsafe { const_eval_select((self as *const u8,), const_impl, runtime_impl) }
}
/// Casts to a pointer of another type.
@ -1587,11 +1598,22 @@ pub const fn is_aligned_to(self, align: usize) -> bool {
panic!("is_aligned_to: align is not a power-of-two");
}
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
self.cast::<()>().align_offset(align) == 0
#[inline]
fn runtime_impl(ptr: *const (), align: usize) -> bool {
ptr.addr() & (align - 1) == 0
}
#[inline]
const fn const_impl(ptr: *const (), align: usize) -> bool {
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
ptr.align_offset(align) == 0
}
// SAFETY: The two versions are equivalent at runtime.
unsafe { const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl) }
}
}

44
library/core/src/ptr/mut_ptr.rs
View File

@ -1,6 +1,6 @@
use super::*;
use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::intrinsics;
use crate::intrinsics::{self, const_eval_select};
use crate::slice::{self, SliceIndex};
impl<T: ?Sized> *mut T {
@ -33,12 +33,23 @@ impl<T: ?Sized> *mut T {
#[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
#[inline]
pub const fn is_null(self) -> bool {
// Compare via a cast to a thin pointer, so fat pointers are only
// considering their "data" part for null-ness.
match (self as *mut u8).guaranteed_eq(null_mut()) {
None => false,
Some(res) => res,
#[inline]
fn runtime_impl(ptr: *mut u8) -> bool {
ptr.addr() == 0
}
#[inline]
const fn const_impl(ptr: *mut u8) -> bool {
// Compare via a cast to a thin pointer, so fat pointers are only
// considering their "data" part for null-ness.
match (ptr).guaranteed_eq(null_mut()) {
None => false,
Some(res) => res,
}
}
// SAFETY: The two versions are equivalent at runtime.
unsafe { const_eval_select((self as *mut u8,), const_impl, runtime_impl) }
}
/// Casts to a pointer of another type.
@ -1859,11 +1870,22 @@ pub const fn is_aligned_to(self, align: usize) -> bool {
panic!("is_aligned_to: align is not a power-of-two");
}
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
self.cast::<()>().align_offset(align) == 0
#[inline]
fn runtime_impl(ptr: *mut (), align: usize) -> bool {
ptr.addr() & (align - 1) == 0
}
#[inline]
const fn const_impl(ptr: *mut (), align: usize) -> bool {
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
ptr.align_offset(align) == 0
}
// SAFETY: The two versions are equivalent at runtime.
unsafe { const_eval_select((self.cast::<()>(), align), const_impl, runtime_impl) }
}
}