Stablilize const_int_{rotate,wrapping,sign} #57105

Centril · 2018-12-24T18:50:48Z

This PR intends to stabilize the following stable methods as const fns:

const_int_rotate
- rotate_left
- rotate_right
const_int_wrapping
- wrapping_add
- wrapping_sub
- wrapping_mul
- wrapping_shl
- wrapping_shr
const_int_sign
- is_positive
- is_negative

(this is the current set; and may be reduced during review...)

r? @oli-obk
(please review this until you think its in a ready state for team review; but don't r+)

cc @RalfJung wrt. state of miri re. the aforementioned methods.
cc #53718

I've added T-lang since this affects intrinsics and the operational semantics of Rust's const fn fragment.
Once @oli-obk thinks its ready for team review I'll fcp-merge.

src/librustc_mir/transform/qualify_min_const_fn.rs

Centril · 2018-12-25T14:04:22Z

@rfcbot fcp merge

Given @oli-obk's approval, I propose that the following set of stable methods should stabilize as const fns given that they are about pure arithmetic and thus there's no world in which we would want to turn this back:

const_int_rotate
- rotate_left
- rotate_right
const_int_wrapping
- wrapping_add
- wrapping_sub
- wrapping_mul
- wrapping_shl
- wrapping_shr
const_int_sign
- is_positive
- is_negative

rfcbot · 2018-12-25T14:04:23Z

SimonSapin · 2018-12-25T17:56:39Z

Why not include const_int_ops and const_int_conversion as well?

            pub const fn count_ones(self) -> u32 { (self as $UnsignedT).count_ones() }
            pub const fn count_zeros(self) -> u32 {
            pub const fn leading_zeros(self) -> u32 {
            pub const fn trailing_zeros(self) -> u32 {
            pub const fn swap_bytes(self) -> Self {
            pub const fn reverse_bits(self) -> Self {
            pub const fn from_be(x: Self) -> Self {
            pub const fn from_le(x: Self) -> Self {
            pub const fn to_be(self) -> Self { // or not to be?
            pub const fn to_le(self) -> Self {
            pub const fn to_be_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn to_le_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn to_ne_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn from_be_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
            pub const fn from_le_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
            pub const fn from_ne_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
            pub const fn count_ones(self) -> u32 {
            pub const fn count_zeros(self) -> u32 {
            pub const fn leading_zeros(self) -> u32 {
            pub const fn trailing_zeros(self) -> u32 {
            pub const fn swap_bytes(self) -> Self {
            pub const fn reverse_bits(self) -> Self {
            pub const fn from_be(x: Self) -> Self {
            pub const fn from_le(x: Self) -> Self {
            pub const fn to_be(self) -> Self { // or not to be?
            pub const fn to_le(self) -> Self {
            pub const fn to_be_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn to_le_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn to_ne_bytes(self) -> [u8; mem::size_of::<Self>()] {
            pub const fn from_be_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
            pub const fn from_le_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
            pub const fn from_ne_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {

Centril · 2018-12-25T18:12:52Z

@SimonSapin Hmm; I think I the reason I didn't go for overflowing_ was that they required let bindings which we don't have yet but that's a different feature gate... and then there was something about transmute which I didn't feel comfortable whitelisting since it opens up for un-const operations...

I'll see how much I can expand the set of methods to stably constify without whitelisting transmute... :)

src/librustc_mir/transform/qualify_min_const_fn.rs

RalfJung · 2018-12-26T11:59:38Z

This adds another unsafe power to const fn: Calling unchecked_shr/shl. However, these intrinsics are unstable, and they are only safely exposed exposed.

That seems fine to me, but do we have tests that check that these intrinsics correctly trigger a CTFE error when called with invalid arguments?

With such tests present, the set of functions proposed right now seems fine to me.

@SimonSapin from a review perspective, IMO it makes sense to have several small stabilizations instead of one big one. As long as we land them all in the same cycle, that still gives a coherent story for the release notes.

Centril · 2018-12-26T17:37:58Z

@RalfJung

This adds another unsafe power to const fn: Calling unchecked_shr/shl. However, these intrinsics are unstable, and they are only safely exposed exposed.

That seems fine to me, but do we have tests that check that these intrinsics correctly trigger a CTFE error when called with invalid arguments?

Great point; I'm not sure; I'll check if we do (or add them)... and in the interim:

@rfcbot concern check-tests-for-unchecked_shrl

Centril · 2018-12-29T12:00:52Z

@RalfJung Some tests already existed, but I've extended them in this PR to be more thorough.

@rfcbot resolve check-tests-for-unchecked_shrl

Centril · 2018-12-29T12:03:42Z

@oli-obk Can you recheck the PR given recent changes?

oli-obk · 2018-12-29T13:10:07Z

I think we should make the overflowing and rotate intrinsics safe just like we did with size_of and align_of

RalfJung · 2018-12-29T13:57:41Z

I've extended them in this PR to be more thorough.

Thanks, that looks great!

Centril · 2018-12-31T03:14:39Z

@oli-obk

I think we should make the overflowing and rotate intrinsics safe just like we did with size_of and align_of

Done in fedfb61 and used in 50152d2.

src/libcore/num/mod.rs

oli-obk · 2018-12-31T09:51:01Z

Just a style nit otherwise everything looks great

Lokathor · 2019-01-05T23:52:21Z

wrapping_neg and overflowing_neg can also be made totally branchless, and thus const, with a little bit of bit fiddling

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6a800d9c97885c1aba464ea3103c86e6

Centril · 2019-01-06T00:23:45Z

wrapping_neg and overflowing_neg can also be made totally branchless, and thus const, with a little bit of bit fiddling

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6a800d9c97885c1aba464ea3103c86e6

Let's discuss this in a PR or another issue if you want; it's sorta off-topic for this PR.

Lokathor · 2019-01-06T00:57:42Z

Can do, I'll open an issue for it.

EDIT: actually I'll open an issue once this PR gets merged, since those depend on this being merged

rfcbot · 2019-01-08T22:25:36Z

🔔 This is now entering its final comment period, as per the review above. 🔔

@oli-obk

…li-obk Const-stabilize `const_int_ops` + `const_ip` r? @oli-obk I've added T-lang since this affects intrinsics and the operational semantics of Rust's `const fn` fragment. This PR depends on rust-lang#57105 but the FCP intent does not. ## Stable APIs proposed for constification + `const_int_ops`: + `count_ones` + `count_zeros` + `leading_zeros` + `trailing_zeros` + `swap_bytes` + `from_be` + `from_le` + `to_be` + `to_le` + `const_ip` + `Ipv4Addr::new` ## Unstable APIs constified + `const_int_conversion`: + `reverse_bits`

@oli-obk

…li-obk Const-stabilize `const_int_ops` + `const_ip` r? @oli-obk I've added T-lang since this affects intrinsics and the operational semantics of Rust's `const fn` fragment. This PR depends on rust-lang#57105 but the FCP intent does not. ## Stable APIs proposed for constification + `const_int_ops`: + `count_ones` + `count_zeros` + `leading_zeros` + `trailing_zeros` + `swap_bytes` + `from_be` + `from_le` + `to_be` + `to_le` + `const_ip` + `Ipv4Addr::new` ## Unstable APIs constified + `const_int_conversion`: + `reverse_bits`

@oli-obk

Const-stabilize `const_int_ops` + `const_ip` r? @oli-obk ## Note for relnotes: This PR includes #57105. I've added T-lang since this affects intrinsics and the operational semantics of Rust's `const fn` fragment. ## Stable APIs proposed for constification + `const_int_ops`: + `count_ones` + `count_zeros` + `leading_zeros` + `trailing_zeros` + `swap_bytes` + `from_be` + `from_le` + `to_be` + `to_le` + `const_ip` + `Ipv4Addr::new` ## Unstable APIs constified + `const_int_conversion`: + `reverse_bits`

Centril · 2019-01-12T04:42:43Z

This is subsumed by #57234 (this didn't get closed due to the last commit, but that isn't important...). Since this is done I'll go ahead and close it out.

Pkgsrc changes: * Bump required rust version to build to 1.32.0. * Adapt patches to changed file locations. * Since we now patch some more vendor/ modules, doctor the corresponding .cargo-checksum.json files accordingly Upstream changes: Version 1.33.0 (2019-02-28) ========================== Language -------- - [You can now use the `cfg(target_vendor)` attribute.][57465] E.g. `#[cfg(target_vendor="apple")] fn main() { println!("Hello Apple!"); }` - [Integer patterns such as in a match expression can now be exhaustive.][56362] E.g. You can have match statement on a `u8` that covers `0..=255` and you would no longer be required to have a `_ => unreachable!()` case. - [You can now have multiple patterns in `if let` and `while let` expressions.][57532] You can do this with the same syntax as a `match` expression. E.g. ```rust enum Creature { Crab(String), Lobster(String), Person(String), } fn main() { let state = Creature::Crab("Ferris"); if let Creature::Crab(name) | Creature::Person(name) = state { println!("This creature's name is: {}", name); } } ``` - [You can now have irrefutable `if let` and `while let` patterns.][57535] Using this feature will by default produce a warning as this behaviour can be unintuitive. E.g. `if let _ = 5 {}` - [You can now use `let` bindings, assignments, expression statements, and irrefutable pattern destructuring in const functions.][57175] - [You can now call unsafe const functions.][57067] E.g. ```rust const unsafe fn foo() -> i32 { 5 } const fn bar() -> i32 { unsafe { foo() } } ``` - [You can now specify multiple attributes in a `cfg_attr` attribute.][57332] E.g. `#[cfg_attr(all(), must_use, optimize)]` - [You can now specify a specific alignment with the `#[repr(packed)]` attribute.][57049] E.g. `#[repr(packed(2))] struct Foo(i16, i32);` is a struct with an alignment of 2 bytes and a size of 6 bytes. - [You can now import an item from a module as an `_`.][56303] This allows you to import a trait's impls, and not have the name in the namespace. E.g. ```rust use std::io::Read as _; // Allowed as there is only one `Read` in the module. pub trait Read {} ``` - [You may now use `Rc`, `Arc`, and `Pin` as method receivers][56805]. Compiler -------- - [You can now set a linker flavor for `rustc` with the `-Clinker-flavor` command line argument.][56351] - [The mininum required LLVM version has been bumped to 6.0.][56642] - [Added support for the PowerPC64 architecture on FreeBSD.][57615] - [The `x86_64-fortanix-unknown-sgx` target support has been upgraded to tier 2 support.][57130] Visit the [platform support][platform-support] page for information on Rust's platform support. - [Added support for the `thumbv7neon-linux-androideabi` and `thumbv7neon-unknown-linux-gnueabihf` targets.][56947] - [Added support for the `x86_64-unknown-uefi` target.][56769] Libraries --------- - [The methods `overflowing_{add, sub, mul, shl, shr}` are now `const` functions for all numeric types.][57566] - [The methods `rotate_left`, `rotate_right`, and `wrapping_{add, sub, mul, shl, shr}` are now `const` functions for all numeric types.][57105] - [The methods `is_positive` and `is_negative` are now `const` functions for all signed numeric types.][57105] - [The `get` method for all `NonZero` types is now `const`.][57167] - [The methods `count_ones`, `count_zeros`, `leading_zeros`, `trailing_zeros`, `swap_bytes`, `from_be`, `from_le`, `to_be`, `to_le` are now `const` for all numeric types.][57234] - [`Ipv4Addr::new` is now a `const` function][57234] Stabilized APIs --------------- - [`unix::FileExt::read_exact_at`] - [`unix::FileExt::write_all_at`] - [`Option::transpose`] - [`Result::transpose`] - [`convert::identity`] - [`pin::Pin`] - [`marker::Unpin`] - [`marker::PhantomPinned`] - [`Vec::resize_with`] - [`VecDeque::resize_with`] - [`Duration::as_millis`] - [`Duration::as_micros`] - [`Duration::as_nanos`] Cargo ----- - [Cargo should now rebuild a crate if a file was modified during the initial build.][cargo/6484] Compatibility Notes ------------------- - The methods `str::{trim_left, trim_right, trim_left_matches, trim_right_matches}` are now deprecated in the standard library, and their usage will now produce a warning. Please use the `str::{trim_start, trim_end, trim_start_matches, trim_end_matches}` methods instead. - The `Error::cause` method has been deprecated in favor of `Error::source` which supports downcasting. [55982]: rust-lang/rust#55982 [56303]: rust-lang/rust#56303 [56351]: rust-lang/rust#56351 [56362]: rust-lang/rust#56362 [56642]: rust-lang/rust#56642 [56769]: rust-lang/rust#56769 [56805]: rust-lang/rust#56805 [56947]: rust-lang/rust#56947 [57049]: rust-lang/rust#57049 [57067]: rust-lang/rust#57067 [57105]: rust-lang/rust#57105 [57130]: rust-lang/rust#57130 [57167]: rust-lang/rust#57167 [57175]: rust-lang/rust#57175 [57234]: rust-lang/rust#57234 [57332]: rust-lang/rust#57332 [57465]: rust-lang/rust#57465 [57532]: rust-lang/rust#57532 [57535]: rust-lang/rust#57535 [57566]: rust-lang/rust#57566 [57615]: rust-lang/rust#57615 [cargo/6484]: rust-lang/cargo#6484 [`unix::FileExt::read_exact_at`]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#method.read_exact_at [`unix::FileExt::write_all_at`]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#method.write_all_at [`Option::transpose`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.transpose [`Result::transpose`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.transpose [`convert::identity`]: https://doc.rust-lang.org/std/convert/fn.identity.html [`pin::Pin`]: https://doc.rust-lang.org/std/pin/struct.Pin.html [`marker::Unpin`]: https://doc.rust-lang.org/stable/std/marker/trait.Unpin.html [`marker::PhantomPinned`]: https://doc.rust-lang.org/nightly/std/marker/struct.PhantomPinned.html [`Vec::resize_with`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.resize_with [`VecDeque::resize_with`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.resize_with [`Duration::as_millis`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_millis [`Duration::as_micros`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_micros [`Duration::as_nanos`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_nanos [platform-support]: https://forge.rust-lang.org/platform-support.html

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Centril force-pushed the stabilizations_const_ints branch from 6cb7bac to d426575 Compare December 29, 2018 11:58

Centril added 7 commits December 31, 2018 03:36

stabilize const_int_wrapping.

7e7c337

stabilize const_int_rotate

e258489

stabilize const_int_sign

eb0597a

const stabilizations: adjust run-pass tests.

d85ec4a

unchecked_{shl,shr}: extend const tests.

35d77fc

qualify_min_const_fn: improve note.

e4c47f9

make some intrinsics safe.

fedfb61

now that some intrisics are safe, use that fact.

50152d2

Centril force-pushed the stabilizations_const_ints branch from d426575 to 50152d2 Compare December 31, 2018 03:12

oli-obk reviewed Dec 31, 2018

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src/libcore/num/mod.rs Outdated Show resolved Hide resolved

fix indentation

09dfafb

This was referenced Dec 31, 2018

Const-stabilize const_int_ops + const_ip #57234

Merged

Summary issue for const-stabilizing const_int_overflowing #57237

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Updated RELEASES.md for 1.33.0 #58227

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Stablilize const_int_{rotate,wrapping,sign} #57105

Stablilize const_int_{rotate,wrapping,sign} #57105

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Stablilize const_int_{rotate,wrapping,sign} #57105

Stablilize const_int_{rotate,wrapping,sign} #57105

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