restrict promotion of `const fn` calls #121557

RalfJung · 2024-02-24T16:19:23Z

We only promote them in const/static initializers, but even that is still unfortunate -- we still cannot add promoteds to required_consts. But we should add them there to make sure it's always okay to evaluate every const we encounter in a MIR body. That effort of not promoting things that can fail to evaluate is tracked in #80619. These const fn calls are the last missing piece.

So I propose that we do not promote const-fn calls in const when that may fail without the entire const failing, thereby completing #80619. Unfortunately we can't just reject promoting these functions outright due to backwards compatibility. So let's see if we can find a hack that makes crater happy...

For the record, this is the crater analysis from when I tried to entirely forbid this kind of promotion. It's a tiny amount of breakage and if we had a nice alternative for code like that, we could conceivably push it through... but sadly, inline const expressions are still blocked on t-lang concerns about post-monomorphization errors and we haven't yet figured out an implementation that can resolve those concerns. So we're forced to make progress via other means, such as terrible hacks like this.

Attempt one: only promote calls on the "safe path" at the beginning of a MIR block. This is the path that starts at the start block and continues via gotos and calls, but stops at the first branch. If we had imposed this restriction before stabilizing if and match in const, this would have definitely been sufficient...

EDIT: Turns out that works. :)
Here's the t-lang nomination comment. And here's the FCP comment.

r? @oli-obk

rustbot · 2024-02-24T16:19:32Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

RalfJung · 2024-02-24T16:19:43Z

@bors try

bors · 2024-02-24T16:20:51Z

⌛ Trying commit 98c587a with merge 80d5fe3...

…<try> restrict promotion of `const fn` calls We only promote them in `const`/`static` initializers, but even that is still unfortunate -- we still cannot add promoteds to required_consts. But we should add them there to make sure it's always okay to evaluate every const we encounter in a MIR body. That effort of not promoting things that can fail to evaluate is tracked in rust-lang#80619. These `const fn` calls are the last missing piece. So I propose that we do not promote const-fn calls in const when that may fail without the entire const failing, thereby completing rust-lang#80619. Unfortunately we can't just reject promoting these functions outright due to backwards compatibility. So let's see if we can find a hack that makes crater happy... Attempt one: only promote calls on the "safe path" at the beginning of a MIR block. This is the path that starts at the start block and continues via gotos and calls, but stops at the first branch. r? `@oli-obk`

bors · 2024-02-24T17:50:18Z

☀️ Try build successful - checks-actions
Build commit: 80d5fe3 (80d5fe37e16a0befb4128414cb6a11d544788c0a)

RalfJung · 2024-02-24T17:50:43Z

@craterbot check

craterbot · 2024-02-24T17:50:51Z

👌 Experiment pr-121557 created and queued.
🤖 Automatically detected try build 80d5fe3
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

tests/ui/rfcs/rfc-1623-static/rfc1623-2.rs

compiler/rustc_mir_transform/src/lib.rs

RalfJung · 2024-02-24T17:53:48Z

@rust-timer build 80d5fe3

rust-timer · 2024-02-24T19:07:08Z

Finished benchmarking commit (80d5fe3): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.1%, 6.3%]	43
Regressions ❌ (secondary)	3.3%	[0.2%, 9.5%]	24
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-1.0%, -0.4%]	7
All ❌✅ (primary)	0.9%	[0.1%, 6.3%]	43

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.4%	[1.9%, 3.0%]	3
Regressions ❌ (secondary)	1.5%	[0.8%, 1.7%]	4
Improvements ✅ (primary)	-1.9%	[-3.1%, -0.8%]	2
Improvements ✅ (secondary)	-4.2%	[-4.2%, -4.2%]	1
All ❌✅ (primary)	0.7%	[-3.1%, 3.0%]	5

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	6.0%	[4.3%, 7.8%]	6
Regressions ❌ (secondary)	5.8%	[4.5%, 6.7%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.0%	[-3.0%, -0.9%]	3
All ❌✅ (primary)	6.0%	[4.3%, 7.8%]	6

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.0%, 0.7%]	35
Regressions ❌ (secondary)	2.9%	[0.2%, 19.2%]	7
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[-0.1%, 0.7%]	36

Bootstrap: 648.482s -> 651.592s (0.48%)
Artifact size: 310.98 MiB -> 311.12 MiB (0.04%)

RalfJung · 2024-02-24T19:20:18Z

Hm, I guess that has to be the extra entries in required_consts? Maybe it's not worth it for a sanity check... or maybe we can somehow add only the promoteds that call functions, not all the others.

I am going to worry about perf once crater looks good.

bors · 2024-02-25T01:57:03Z

☔ The latest upstream changes (presumably #121569) made this pull request unmergeable. Please resolve the merge conflicts.

craterbot · 2024-03-08T19:49:01Z

🚧 Experiment pr-121557 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2024-03-10T09:18:17Z

🎉 Experiment pr-121557 is completed!
📊 93 regressed and 1 fixed (420397 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

RalfJung · 2024-03-10T10:06:18Z

Ah, I screwed up the logic and now it no longer promotes #[rustc_promotable] functions after control flow. That will account for many of these regressions. Fixed it, let's re-run the failed crates.

@bors try

…without the entire const failing

…fail

… can fail

then we can also make all_required_consts_are_checked a constant instead of a function

RalfJung · 2024-04-23T21:03:28Z

@bors r=oli-obk rollup=iffy

bors · 2024-04-23T21:03:30Z

📌 Commit 8436045 has been approved by oli-obk

It is now in the queue for this repository.

bors · 2024-04-23T22:51:05Z

⌛ Testing commit 8436045 with merge fee0e66...

bors · 2024-04-24T00:54:02Z

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing fee0e66 to master...

rust-timer · 2024-04-24T02:20:36Z

Finished benchmarking commit (fee0e66): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.3%	[1.3%, 1.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.1%	[0.0%, 0.2%]	16
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[0.0%, 0.2%]	16

Bootstrap: 674.182s -> 675.372s (0.18%)
Artifact size: 316.23 MiB -> 316.22 MiB (-0.00%)

This is based on the pkgsrc-wip rust180 package, retaining the main pkgsrc changes as best as I could. Pkgsrc changes: * Adapt checksums and patches. * Make this work again on big-endian aarch64 (at least on NetBSD). * Make the choice of GCC = 12 work for sparc64 by testing options after options.mk is included (which is required...). Makes this work on NetBSD/sparc64 10.0 again. Upstream chnages: Version 1.80.1 (2024-08-08) =========================== - [Fix miscompilation in the jump threading MIR optimization when comparing floats] (rust-lang/rust#128271) - [Revert changes to the `dead_code` lint from 1.80.0] (rust-lang/rust#128618) Version 1.80.0 (2024-07-25) ========================== Language -------- - [Document maximum allocation size] (rust-lang/rust#116675) - [Allow zero-byte offsets and ZST read/writes on arbitrary pointers] (rust-lang/rust#117329) - [Support C23's variadics without a named parameter] (rust-lang/rust#124048) - [Stabilize `exclusive_range_pattern` feature] (rust-lang/rust#124459) - [Guarantee layout and ABI of `Result` in some scenarios] (rust-lang/rust#124870) Compiler -------- - [Update cc crate to v1.0.97 allowing additional spectre mitigations on MSVC targets] (rust-lang/rust#124892) - [Allow field reordering on types marked `repr(packed(1))`] (rust-lang/rust#125360) - [Add a lint against never type fallback affecting unsafe code] (rust-lang/rust#123939) - [Disallow cast with trailing braced macro in let-else] (rust-lang/rust#125049) - [Expand `for_loops_over_fallibles` lint to lint on fallibles behind references.] (rust-lang/rust#125156) - [self-contained linker: retry linking without `-fuse-ld=lld` on CCs that don't support it] (rust-lang/rust#125417) - [Do not parse CVarArgs (`...`) as a type in trait bounds] (rust-lang/rust#125863) - Improvements to LLDB formatting [#124458] (rust-lang/rust#124458) [#124500] (rust-lang/rust#124500) - [For the wasm32-wasip2 target default to PIC and do not use `-fuse-ld=lld`] (rust-lang/rust#124858) - [Add x86_64-unknown-linux-none as a tier 3 target] (rust-lang/rust#125023) - [Lint on `foo.into_iter()` resolving to `&Box<[T]>: IntoIterator`] (rust-lang/rust#124097) Libraries --------- - [Add `size_of` and `size_of_val` and `align_of` and `align_of_val` to the prelude] (rust-lang/rust#123168) - [Abort a process when FD ownership is violated] (rust-lang/rust#124210) - [io::Write::write_fmt: panic if the formatter fails when the stream does not fail] (rust-lang/rust#125012) - [Panic if `PathBuf::set_extension` would add a path separator] (rust-lang/rust#125070) - [Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods] (rust-lang/rust#121571) - [Update `c_char` on AIX to use the correct type] (rust-lang/rust#122986) - [`offset_of!` no longer returns a temporary] (rust-lang/rust#124484) - [Handle sigma in `str.to_lowercase` correctly] (rust-lang/rust#124773) - [Raise `DEFAULT_MIN_STACK_SIZE` to at least 64KiB] (rust-lang/rust#126059) Stabilized APIs --------------- - [`impl Default for Rc<CStr>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3CCStr%3E) - [`impl Default for Rc<str>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3Cstr%3E) - [`impl Default for Rc<[T]>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3C%5BT%5D%3E) - [`impl Default for Arc<str>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3Cstr%3E) - [`impl Default for Arc<CStr>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3CCStr%3E) - [`impl Default for Arc<[T]>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3C%5BT%5D%3E) - [`impl IntoIterator for Box<[T]>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-IntoIterator-for-Box%3C%5BI%5D,+A%3E) - [`impl FromIterator<String> for Box<str>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3CString%3E-for-Box%3Cstr%3E) - [`impl FromIterator<char> for Box<str>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3Cchar%3E-for-Box%3Cstr%3E) - [`LazyCell`] (https://doc.rust-lang.org/beta/core/cell/struct.LazyCell.html) - [`LazyLock`] (https://doc.rust-lang.org/beta/std/sync/struct.LazyLock.html) - [`Duration::div_duration_f32`] (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f32) - [`Duration::div_duration_f64`] (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f64) - [`Option::take_if`] (https://doc.rust-lang.org/beta/std/option/enum.Option.html#method.take_if) - [`Seek::seek_relative`] (https://doc.rust-lang.org/beta/std/io/trait.Seek.html#method.seek_relative) - [`BinaryHeap::as_slice`] (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.as_slice) - [`NonNull::offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset) - [`NonNull::byte_offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset) - [`NonNull::add`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.add) - [`NonNull::byte_add`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_add) - [`NonNull::sub`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.sub) - [`NonNull::byte_sub`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_sub) - [`NonNull::offset_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset_from) - [`NonNull::byte_offset_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset_from) - [`NonNull::read`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read) - [`NonNull::read_volatile`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_volatile) - [`NonNull::read_unaligned`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_unaligned) - [`NonNull::write`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write) - [`NonNull::write_volatile`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_volatile) - [`NonNull::write_unaligned`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_unaligned) - [`NonNull::write_bytes`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_bytes) - [`NonNull::copy_to`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to) - [`NonNull::copy_to_nonoverlapping`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to_nonoverlapping) - [`NonNull::copy_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from) - [`NonNull::copy_from_nonoverlapping`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from_nonoverlapping) - [`NonNull::replace`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.replace) - [`NonNull::swap`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.swap) - [`NonNull::drop_in_place`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.drop_in_place) - [`NonNull::align_offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.align_offset) - [`<[T]>::split_at_checked`] (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_checked) - [`<[T]>::split_at_mut_checked`] (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_mut_checked) - [`str::split_at_checked`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_checked) - [`str::split_at_mut_checked`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_mut_checked) - [`str::trim_ascii`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii) - [`str::trim_ascii_start`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_start) - [`str::trim_ascii_end`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_end) - [`<[u8]>::trim_ascii`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii) - [`<[u8]>::trim_ascii_start`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_start) - [`<[u8]>::trim_ascii_end`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_end) - [`Ipv4Addr::BITS`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#associatedconstant.BITS) - [`Ipv4Addr::to_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.to_bits) - [`Ipv4Addr::from_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.from_bits) - [`Ipv6Addr::BITS`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#associatedconstant.BITS) - [`Ipv6Addr::to_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.to_bits) - [`Ipv6Addr::from_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.from_bits) - [`Vec::<[T; N]>::into_flattened`] (https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html#method.into_flattened) - [`<[[T; N]]>::as_flattened`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened) - [`<[[T; N]]>::as_flattened_mut`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened_mut) These APIs are now stable in const contexts: - [`<[T]>::last_chunk`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.last_chunk) - [`BinaryHeap::new`] (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.new) Cargo ----- - [Stabilize `-Zcheck-cfg` as always enabled] (rust-lang/cargo#13571) - [Warn, rather than fail publish, if a target is excluded] (rust-lang/cargo#13713) - [Add special `check-cfg` lint config for the `unexpected_cfgs` lint] (rust-lang/cargo#13913) - [Stabilize `cargo update --precise <yanked>`] (rust-lang/cargo#13974) - [Don't change file permissions on `Cargo.toml` when using `cargo add`] (rust-lang/cargo#13898) - [Support using `cargo fix` on IPv6-only networks] (rust-lang/cargo#13907) Rustdoc ----- - [Allow searching for references] (rust-lang/rust#124148) - [Stabilize `custom_code_classes_in_docs` feature] (rust-lang/rust#124577) - [fix: In cross-crate scenarios show enum variants on type aliases of enums] (rust-lang/rust#125300) Compatibility Notes ------------------- - [rustfmt estimates line lengths differently when using non-ascii characters] (rust-lang/rustfmt#6203) - [Type aliases are now handled correctly in orphan check] (rust-lang/rust#117164) - [Allow instructing rustdoc to read from stdin via `-`] (rust-lang/rust#124611) - [`std::env::{set_var, remove_var}` can no longer be converted to safe function pointers and no longer implement the `Fn` family of traits] (rust-lang/rust#124636) - [Warn (or error) when `Self` constructor from outer item is referenced in inner nested item] (rust-lang/rust#124187) - [Turn `indirect_structural_match` and `pointer_structural_match` lints into hard errors] (rust-lang/rust#124661) - [Make `where_clause_object_safety` lint a regular object safety violation] (rust-lang/rust#125380) - [Turn `proc_macro_back_compat` lint into a hard error.] (rust-lang/rust#125596) - [Detect unused structs even when implementing private traits] (rust-lang/rust#122382) - [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`] (rust-lang/rust#125527) which means [`std::io::StdoutLock` and `std::io::StderrLock` are no longer Sync] (rust-lang/rust#127340) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - Misc improvements to size of generated html by rustdoc e.g. [#124738] (rust-lang/rust#124738) and [#123734] (rust-lang/rust#123734) - [MSVC targets no longer depend on libc] (rust-lang/rust#124050) Version 1.79.0 (2024-06-13) ========================== Language -------- - [Stabilize inline `const {}` expressions.] (rust-lang/rust#104087) - [Prevent opaque types being instantiated twice with different regions within the same function.] (rust-lang/rust#116935) - [Stabilize WebAssembly target features that are in phase 4 and 5.] (rust-lang/rust#117457) - [Add the `redundant_lifetimes` lint to detect lifetimes which are semantically redundant.] (rust-lang/rust#118391) - [Stabilize the `unnameable_types` lint for public types that can't be named.] (rust-lang/rust#120144) - [Enable debuginfo in macros, and stabilize `-C collapse-macro-debuginfo` and `#[collapse_debuginfo]`.] (rust-lang/rust#120845) - [Propagate temporary lifetime extension into `if` and `match` expressions.] (rust-lang/rust#121346) - [Restrict promotion of `const fn` calls.] (rust-lang/rust#121557) - [Warn against refining impls of crate-private traits with `refining_impl_trait` lint.] (rust-lang/rust#121720) - [Stabilize associated type bounds (RFC 2289).] (rust-lang/rust#122055) - [Stabilize importing `main` from other modules or crates.] (rust-lang/rust#122060) - [Check return types of function types for well-formedness] (rust-lang/rust#115538) - [Rework `impl Trait` lifetime inference] (rust-lang/rust#116891) - [Change inductive trait solver cycles to be ambiguous] (rust-lang/rust#122791) Compiler -------- - [Define `-C strip` to only affect binaries, not artifacts like `.pdb`.] (rust-lang/rust#115120) - [Stabilize `-Crelro-level` for controlling runtime link hardening.] (rust-lang/rust#121694) - [Stabilize checking of `cfg` names and values at compile-time with `--check-cfg`.] (rust-lang/rust#123501) *Note that this only stabilizes the compiler part, the Cargo part is still unstable in this release.* - [Add `aarch64-apple-visionos` and `aarch64-apple-visionos-sim` tier 3 targets.] (rust-lang/rust#121419) - [Add `riscv32ima-unknown-none-elf` tier 3 target.] (rust-lang/rust#122696) - [Promote several Windows targets to tier 2] (rust-lang/rust#121712): `aarch64-pc-windows-gnullvm`, `i686-pc-windows-gnullvm`, and `x86_64-pc-windows-gnullvm`. Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Implement `FromIterator` for `(impl Default + Extend, impl Default + Extend)`.] (rust-lang/rust#107462) - [Implement `{Div,Rem}Assign<NonZero<X>>` on `X`.] (rust-lang/rust#121952) - [Document overrides of `clone_from()` in core/std.] (rust-lang/rust#122201) - [Link MSVC default lib in core.] (rust-lang/rust#122268) - [Caution against using `transmute` between pointers and integers.] (rust-lang/rust#122379) - [Enable frame pointers for the standard library.] (rust-lang/rust#122646) Stabilized APIs --------------- - [`{integer}::unchecked_add`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add) - [`{integer}::unchecked_mul`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul) - [`{integer}::unchecked_sub`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub) - [`<[T]>::split_at_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked) - [`<[T]>::split_at_mut_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked) - [`<[u8]>::utf8_chunks`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks) - [`str::Utf8Chunks`] (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html) - [`str::Utf8Chunk`] (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html) - [`<*const T>::is_aligned`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned) - [`<*mut T>::is_aligned`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1) - [`NonNull::is_aligned`] (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned) - [`<*const [T]>::len`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len) - [`<*mut [T]>::len`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1) - [`<*const [T]>::is_empty`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty) - [`<*mut [T]>::is_empty`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1) - [`NonNull::<[T]>::is_empty`] (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty) - [`CStr::count_bytes`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) - [`io::Error::downcast`] (https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast) - [`num::NonZero<T>`] (https://doc.rust-lang.org/stable/core/num/struct.NonZero.html) - [`path::absolute`] (https://doc.rust-lang.org/stable/std/path/fn.absolute.html) - [`proc_macro::Literal::byte_character`] (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character) - [`proc_macro::Literal::c_string`] (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string) These APIs are now stable in const contexts: - [`Atomic*::into_inner`] (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner) - [`io::Cursor::new`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new) - [`io::Cursor::get_ref`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref) - [`io::Cursor::position`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position) - [`io::empty`] (https://doc.rust-lang.org/stable/std/io/fn.empty.html) - [`io::repeat`] (https://doc.rust-lang.org/stable/std/io/fn.repeat.html) - [`io::sink`] (https://doc.rust-lang.org/stable/std/io/fn.sink.html) - [`panic::Location::caller`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller) - [`panic::Location::file`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file) - [`panic::Location::line`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line) - [`panic::Location::column`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column) Cargo ----- - [Prevent dashes in `lib.name`, always normalizing to `_`.] (rust-lang/cargo#12783) - [Stabilize MSRV-aware version requirement selection in `cargo add`.] (rust-lang/cargo#13608) - [Switch to using `gitoxide` by default for listing files.] (rust-lang/cargo#13696) Rustdoc ----- - [Always display stability version even if it's the same as the containing item.] (rust-lang/rust#118441) - [Show a single search result for items with multiple paths.] (rust-lang/rust#119912) - [Support typing `/` in docs to begin a search.] (rust-lang/rust#123355) Misc ---- Compatibility Notes ------------------- - [Update the minimum external LLVM to 17.] (rust-lang/rust#122649) - [`RustcEncodable` and `RustcDecodable` are soft-destabilized, to be removed from the prelude in next edition.] (rust-lang/rust#116016) - [The `wasm_c_abi` future-incompatibility lint will warn about use of the non-spec-compliant C ABI.] (rust-lang/rust#117918) Use `wasm-bindgen v0.2.88` to generate forward-compatible bindings. - [Check return types of function types for well-formedness] (rust-lang/rust#115538) Version 1.78.0 (2024-05-02) =========================== Language -------- - [Stabilize `#[cfg(target_abi = ...)]`] (rust-lang/rust#119590) - [Stabilize the `#[diagnostic]` namespace and `#[diagnostic::on_unimplemented]` attribute] (rust-lang/rust#119888) - [Make async-fn-in-trait implementable with concrete signatures] (rust-lang/rust#120103) - [Make matching on NaN a hard error, and remove the rest of `illegal_floating_point_literal_pattern`] (rust-lang/rust#116284) - [static mut: allow mutable reference to arbitrary types, not just slices and arrays] (rust-lang/rust#117614) - [Extend `invalid_reference_casting` to include references casting to bigger memory layout] (rust-lang/rust#118983) - [Add `non_contiguous_range_endpoints` lint for singleton gaps after exclusive ranges] (rust-lang/rust#118879) - [Add `wasm_c_abi` lint for use of older wasm-bindgen versions] (rust-lang/rust#117918) This lint currently only works when using Cargo. - [Update `indirect_structural_match` and `pointer_structural_match` lints to match RFC] (rust-lang/rust#120423) - [Make non-`PartialEq`-typed consts as patterns a hard error] (rust-lang/rust#120805) - [Split `refining_impl_trait` lint into `_reachable`, `_internal` variants] (rust-lang/rust#121720) - [Remove unnecessary type inference when using associated types inside of higher ranked `where`-bounds] (rust-lang/rust#119849) - [Weaken eager detection of cyclic types during type inference] (rust-lang/rust#119989) - [`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Auto`] (rust-lang/rust#119338) Compiler -------- - [Made `INVALID_DOC_ATTRIBUTES` lint deny by default] (rust-lang/rust#111505) - [Increase accuracy of redundant `use` checking] (rust-lang/rust#117772) - [Suggest moving definition if non-found macro_rules! is defined later] (rust-lang/rust#121130) - [Lower transmutes from int to pointer type as gep on null] (rust-lang/rust#121282) Target changes: - [Windows tier 1 targets now require at least Windows 10] (rust-lang/rust#115141) - [Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows] (rust-lang/rust#120820) - [Add `wasm32-wasip1` tier 2 (without host tools) target] (rust-lang/rust#120468) - [Add `wasm32-wasip2` tier 3 target] (rust-lang/rust#119616) - [Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`] (rust-lang/rust#122170) - [Add `arm64ec-pc-windows-msvc` tier 3 target] (rust-lang/rust#119199) - [Add `armv8r-none-eabihf` tier 3 target for the Cortex-R52] (rust-lang/rust#110482) - [Add `loongarch64-unknown-linux-musl` tier 3 target] (rust-lang/rust#121832) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Bump Unicode to version 15.1.0, regenerate tables] (rust-lang/rust#120777) - [Make align_offset, align_to well-behaved in all cases] (rust-lang/rust#121201) - [PartialEq, PartialOrd: document expectations for transitive chains] (rust-lang/rust#115386) - [Optimize away poison guards when std is built with panic=abort] (rust-lang/rust#100603) - [Replace pthread `RwLock` with custom implementation] (rust-lang/rust#110211) - [Implement unwind safety for Condvar on all platforms] (rust-lang/rust#121768) - [Add ASCII fast-path for `char::is_grapheme_extended`] (rust-lang/rust#121138) Stabilized APIs --------------- - [`impl Read for &Stdin`] (https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#impl-Read-for-%26Stdin) - [Accept non `'static` lifetimes for several `std::error::Error` related implementations] (rust-lang/rust#113833) - [Make `impl<Fd: AsFd>` impl take `?Sized`] (rust-lang/rust#114655) - [`impl From<TryReserveError> for io::Error`] (https://doc.rust-lang.org/stable/std/io/struct.Error.html#impl-From%3CTryReserveError%3E-for-Error) These APIs are now stable in const contexts: - [`Barrier::new()`] (https://doc.rust-lang.org/stable/std/sync/struct.Barrier.html#method.new) Cargo ----- - [Stabilize lockfile v4](rust-lang/cargo#12852) - [Respect `rust-version` when generating lockfile] (rust-lang/cargo#12861) - [Control `--charset` via auto-detecting config value] (rust-lang/cargo#13337) - [Support `target.<triple>.rustdocflags` officially] (rust-lang/cargo#13197) - [Stabilize global cache data tracking] (rust-lang/cargo#13492) Misc ---- - [rustdoc: add `--test-builder-wrapper` arg to support wrappers such as RUSTC_WRAPPER when building doctests] (rust-lang/rust#114651) Compatibility Notes ------------------- - [Many unsafe precondition checks now run for user code with debug assertions enabled] (rust-lang/rust#120594) This change helps users catch undefined behavior in their code, though the details of how much is checked are generally not stable. - [riscv only supports split_debuginfo=off for now] (rust-lang/rust#120518) - [Consistently check bounds on hidden types of `impl Trait`] (rust-lang/rust#121679) - [Change equality of higher ranked types to not rely on subtyping] (rust-lang/rust#118247) - [When called, additionally check bounds on normalized function return type] (rust-lang/rust#118882) - [Expand coverage for `arithmetic_overflow` lint] (rust-lang/rust#119432) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Update to LLVM 18](rust-lang/rust#120055) - [Build `rustc` with 1CGU on `x86_64-pc-windows-msvc`] (rust-lang/rust#112267) - [Build `rustc` with 1CGU on `x86_64-apple-darwin`] (rust-lang/rust#112268) - [Introduce `run-make` V2 infrastructure, a `run_make_support` library and port over 2 tests as example] (rust-lang/rust#113026) - [Windows: Implement condvar, mutex and rwlock using futex] (rust-lang/rust#121956) Version 1.77.0 (2024-03-21) ========================== - [Reveal opaque types within the defining body for exhaustiveness checking.] (rust-lang/rust#116821) - [Stabilize C-string literals.] (rust-lang/rust#117472) - [Stabilize THIR unsafeck.] (rust-lang/rust#117673) - [Add lint `static_mut_refs` to warn on references to mutable statics.] (rust-lang/rust#117556) - [Support async recursive calls (as long as they have indirection).] (rust-lang/rust#117703) - [Undeprecate lint `unstable_features` and make use of it in the compiler.] (rust-lang/rust#118639) - [Make inductive cycles in coherence ambiguous always.] (rust-lang/rust#118649) - [Get rid of type-driven traversal in const-eval interning] (rust-lang/rust#119044), only as a [future compatiblity lint] (rust-lang/rust#122204) for now. - [Deny braced macro invocations in let-else.] (rust-lang/rust#119062) Compiler -------- - [Include lint `soft_unstable` in future breakage reports.] (rust-lang/rust#116274) - [Make `i128` and `u128` 16-byte aligned on x86-based targets.] (rust-lang/rust#116672) - [Use `--verbose` in diagnostic output.] (rust-lang/rust#119129) - [Improve spacing between printed tokens.] (rust-lang/rust#120227) - [Merge the `unused_tuple_struct_fields` lint into `dead_code`.] (rust-lang/rust#118297) - [Error on incorrect implied bounds in well-formedness check] (rust-lang/rust#118553), with a temporary exception for Bevy. - [Fix coverage instrumentation/reports for non-ASCII source code.] (rust-lang/rust#119033) - [Fix `fn`/`const` items implied bounds and well-formedness check.] (rust-lang/rust#120019) - [Promote `riscv32{im|imafc}-unknown-none-elf` targets to tier 2.] (rust-lang/rust#118704) - Add several new tier 3 targets: - [`aarch64-unknown-illumos`] (rust-lang/rust#112936) - [`hexagon-unknown-none-elf`] (rust-lang/rust#117601) - [`riscv32imafc-esp-espidf`] (rust-lang/rust#119738) - [`riscv32im-risc0-zkvm-elf`] (rust-lang/rust#117958) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Implement `From<&[T; N]>` for `Cow<[T]>`.] (rust-lang/rust#113489) - [Remove special-case handling of `vec.split_off (0)`.](rust-lang/rust#119917) Stabilized APIs --------------- - [`array::each_ref`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref) - [`array::each_mut`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut) - [`core::net`] (https://doc.rust-lang.org/stable/core/net/index.html) - [`f32::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.round_ties_even) - [`f64::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.round_ties_even) - [`mem::offset_of!`] (https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html) - [`slice::first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk) - [`slice::first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk_mut) - [`slice::split_first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk) - [`slice::split_first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk_mut) - [`slice::last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk) - [`slice::last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk_mut) - [`slice::split_last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk) - [`slice::split_last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk_mut) - [`slice::chunk_by`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by) - [`slice::chunk_by_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by_mut) - [`Bound::map`] (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.map) - [`File::create_new`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.create_new) - [`Mutex::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.clear_poison) - [`RwLock::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.RwLock.html#method.clear_poison) Cargo ----- - [Extend the build directive syntax with `cargo::`.] (rust-lang/cargo#12201) - [Stabilize metadata `id` format as `PackageIDSpec`.] (rust-lang/cargo#12914) - [Pull out as `cargo-util-schemas` as a crate.] (rust-lang/cargo#13178) - [Strip all debuginfo when debuginfo is not requested.] (rust-lang/cargo#13257) - [Inherit jobserver from env for all kinds of runners.] (rust-lang/cargo#12776) - [Deprecate rustc plugin support in cargo.] (rust-lang/cargo#13248) Rustdoc ----- - [Allows links in markdown headings.] (rust-lang/rust#117662) - [Search for tuples and unit by type with `()`.] (rust-lang/rust#118194) - [Clean up the source sidebar's hide button.] (rust-lang/rust#119066) - [Prevent JS injection from `localStorage`.] (rust-lang/rust#120250) Misc ---- - [Recommend version-sorting for all sorting in style guide.] (rust-lang/rust#115046) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add more weirdness to `weird-exprs.rs`.] (rust-lang/rust#119028)

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RalfJung force-pushed the const-fn-call-promotion branch from 98c587a to 55dbcde Compare February 24, 2024 17:50

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RalfJung added 3 commits April 23, 2024 22:52

promotion: do not promote const-fn calls in const when that may fail …

7183fa0

…without the entire const failing

compute required_consts before promotion, and add promoteds that may …

b2b617a

…fail

interpret: sanity-check that required_consts captures all consts that…

bf021ea

… can fail

RalfJung force-pushed the const-fn-call-promotion branch from 85433c4 to 5237c33 Compare April 23, 2024 20:52

RalfJung added 2 commits April 23, 2024 23:02

properly fill a promoted's required_consts

173d1bd

then we can also make all_required_consts_are_checked a constant instead of a function

filter required_consts during inlining

8436045

RalfJung force-pushed the const-fn-call-promotion branch from 5237c33 to 8436045 Compare April 23, 2024 21:03

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bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 24, 2024

bors merged commit fee0e66 into rust-lang:master Apr 24, 2024
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RalfJung deleted the const-fn-call-promotion branch April 24, 2024 07:13

This was referenced Apr 24, 2024

Clean up implicit const promotion behavior #124328

Open

Tracking Issue for infallible promotion #80619

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matthiaskrgr mentioned this pull request Apr 24, 2024

ICE: interpret const eval failure of Unevaluated(UnevaluatedConst ... which is not in required_consts #124348

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apiraino removed the to-announce Announce this issue on triage meeting label Apr 29, 2024

RalfJung added the relnotes Marks issues that should be documented in the release notes of the next release. label Apr 29, 2024

This was referenced Jun 16, 2024

1.79 regression in const temporary lifetime extension #126562

Closed

include_dir generates function calls that need promotion, leading to issues with Rust 1.79+ Michael-F-Bryan/include_dir#99

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PaulDance mentioned this pull request Jul 17, 2024

Manual block encodings madsmtm/objc2#636

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saethlin mentioned this pull request Sep 22, 2024

ICE: interpret const eval failure of Unevaluated(UnevaluatedConst #130687

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restrict promotion of `const fn` calls #121557

restrict promotion of `const fn` calls #121557

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restrict promotion of const fn calls #121557

restrict promotion of const fn calls #121557

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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Overall result: ❌ regressions - no action needed

restrict promotion of `const fn` calls #121557

restrict promotion of `const fn` calls #121557

RalfJung commented Feb 24, 2024 •

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