Rollup of 5 pull requests #72226

RalfJung · 2020-05-15T06:42:01Z

Successful merges:

Rework the std::iter::Step trait #69659 (Rework the std::iter::Step trait)
Miri interning: replace ICEs by proper errors #71665 (Miri interning: replace ICEs by proper errors)
Be less aggressive with DroplessArena/TypedArena growth. #71872 (Be less aggressive with DroplessArena/TypedArena growth.)
Update transitive dependency to work towards removing syn <1.0 dep #71919 (Update transitive dependency to work towards removing syn <1.0 dep)
rustc_driver: factor out computing the exit code #72090 (rustc_driver: factor out computing the exit code)

Failed merges:

Co-Authored-By: Nadrieril Feneanar <nadrieril@users.noreply.github.com>

…pe signature more precise

Co-Authored-By: Oliver Scherer <github35764891676564198441@oli-obk.de>

For the given code paths, the amount of space used in the previous chunk is irrelevant. (This will almost never make a difference to behaviour, but it makes the code clearer.)

`DroplessArena` and `TypedArena` use an aggressive growth strategy: the first chunk is 4 KiB, the second is 8 KiB, and it keeps on doubling indefinitely. DHAT profiles show that sometimes this results in large chunks (e.g. 16-128 MiB) that are barely filled. Although these don't contribute to RSS, they clog up the DHAT profiles. This commit changes things so that the doubling stops at 2 MiB. This is large enough that chunk allocations are still rare (you might get 100s instead of 10s of them) but avoids lots of unused space in the worst case. It gives a slight speed-up to cycle counts in some cases.

The previous definition did not optimize down to a single add operation, but this version does appear to.

Rework the std::iter::Step trait Previous attempts: rust-lang#43127 rust-lang#62886 rust-lang#68807 Tracking issue: rust-lang#42168 This PR reworks the `Step` trait to be phrased in terms of the *successor* and *predecessor* operations. With this, `Step` hopefully has a consistent identity that can have a path towards stabilization. The proposed trait: ```rust /// Objects that have a notion of *successor* and *predecessor* operations. /// /// The *successor* operation moves towards values that compare greater. /// The *predecessor* operation moves towards values that compare lesser. /// /// # Safety /// /// This trait is `unsafe` because its implementation must be correct for /// the safety of `unsafe trait TrustedLen` implementations, and the results /// of using this trait can otherwise be trusted by `unsafe` code to be correct /// and fulful the listed obligations. pub unsafe trait Step: Clone + PartialOrd + Sized { /// Returns the number of *successor* steps required to get from `start` to `end`. /// /// Returns `None` if the number of steps would overflow `usize` /// (or is infinite, or if `end` would never be reached). /// /// # Invariants /// /// For any `a`, `b`, and `n`: /// /// * `steps_between(&a, &b) == Some(n)` if and only if `Step::forward(&a, n) == Some(b)` /// * `steps_between(&a, &b) == Some(n)` if and only if `Step::backward(&a, n) == Some(a)` /// * `steps_between(&a, &b) == Some(n)` only if `a <= b` /// * Corollary: `steps_between(&a, &b) == Some(0)` if and only if `a == b` /// * Note that `a <= b` does _not_ imply `steps_between(&a, &b) != None`; /// this is the case wheen it would require more than `usize::MAX` steps to get to `b` /// * `steps_between(&a, &b) == None` if `a > b` fn steps_between(start: &Self, end: &Self) -> Option<usize>; /// Returns the value that would be obtained by taking the *successor* /// of `self` `count` times. /// /// If this would overflow the range of values supported by `Self`, returns `None`. /// /// # Invariants /// /// For any `a`, `n`, and `m`: /// /// * `Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == Step::forward_checked(a, m).and_then(|x| Step::forward_checked(x, n))` /// /// For any `a`, `n`, and `m` where `n + m` does not overflow: /// /// * `Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == Step::forward_checked(a, n + m)` /// /// For any `a` and `n`: /// /// * `Step::forward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::forward_checked(&x, 1))` /// * Corollary: `Step::forward_checked(&a, 0) == Some(a)` fn forward_checked(start: Self, count: usize) -> Option<Self>; /// Returns the value that would be obtained by taking the *successor* /// of `self` `count` times. /// /// If this would overflow the range of values supported by `Self`, /// this function is allowed to panic, wrap, or saturate. /// The suggested behavior is to panic when debug assertions are enabled, /// and to wrap or saturate otherwise. /// /// Unsafe code should not rely on the correctness of behavior after overflow. /// /// # Invariants /// /// For any `a`, `n`, and `m`, where no overflow occurs: /// /// * `Step::forward(Step::forward(a, n), m) == Step::forward(a, n + m)` /// /// For any `a` and `n`, where no overflow occurs: /// /// * `Step::forward_checked(a, n) == Some(Step::forward(a, n))` /// * `Step::forward(a, n) == (0..n).fold(a, |x, _| Step::forward(x, 1))` /// * Corollary: `Step::forward(a, 0) == a` /// * `Step::forward(a, n) >= a` /// * `Step::backward(Step::forward(a, n), n) == a` fn forward(start: Self, count: usize) -> Self { Step::forward_checked(start, count).expect("overflow in `Step::forward`") } /// Returns the value that would be obtained by taking the *successor* /// of `self` `count` times. /// /// # Safety /// /// It is undefined behavior for this operation to overflow the /// range of values supported by `Self`. If you cannot guarantee that this /// will not overflow, use `forward` or `forward_checked` instead. /// /// # Invariants /// /// For any `a`: /// /// * if there exists `b` such that `b > a`, it is safe to call `Step::forward_unchecked(a, 1)` /// * if there exists `b`, `n` such that `steps_between(&a, &b) == Some(n)`, /// it is safe to call `Step::forward_unchecked(a, m)` for any `m <= n`. /// /// For any `a` and `n`, where no overflow occurs: /// /// * `Step::forward_unchecked(a, n)` is equivalent to `Step::forward(a, n)` #[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")] unsafe fn forward_unchecked(start: Self, count: usize) -> Self { Step::forward(start, count) } /// Returns the value that would be obtained by taking the *successor* /// of `self` `count` times. /// /// If this would overflow the range of values supported by `Self`, returns `None`. /// /// # Invariants /// /// For any `a`, `n`, and `m`: /// /// * `Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == n.checked_add(m).and_then(|x| Step::backward_checked(a, x))` /// * `Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == try { Step::backward_checked(a, n.checked_add(m)?) }` /// /// For any `a` and `n`: /// /// * `Step::backward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::backward_checked(&x, 1))` /// * Corollary: `Step::backward_checked(&a, 0) == Some(a)` fn backward_checked(start: Self, count: usize) -> Option<Self>; /// Returns the value that would be obtained by taking the *predecessor* /// of `self` `count` times. /// /// If this would overflow the range of values supported by `Self`, /// this function is allowed to panic, wrap, or saturate. /// The suggested behavior is to panic when debug assertions are enabled, /// and to wrap or saturate otherwise. /// /// Unsafe code should not rely on the correctness of behavior after overflow. /// /// # Invariants /// /// For any `a`, `n`, and `m`, where no overflow occurs: /// /// * `Step::backward(Step::backward(a, n), m) == Step::backward(a, n + m)` /// /// For any `a` and `n`, where no overflow occurs: /// /// * `Step::backward_checked(a, n) == Some(Step::backward(a, n))` /// * `Step::backward(a, n) == (0..n).fold(a, |x, _| Step::backward(x, 1))` /// * Corollary: `Step::backward(a, 0) == a` /// * `Step::backward(a, n) <= a` /// * `Step::forward(Step::backward(a, n), n) == a` fn backward(start: Self, count: usize) -> Self { Step::backward_checked(start, count).expect("overflow in `Step::backward`") } /// Returns the value that would be obtained by taking the *predecessor* /// of `self` `count` times. /// /// # Safety /// /// It is undefined behavior for this operation to overflow the /// range of values supported by `Self`. If you cannot guarantee that this /// will not overflow, use `backward` or `backward_checked` instead. /// /// # Invariants /// /// For any `a`: /// /// * if there exists `b` such that `b < a`, it is safe to call `Step::backward_unchecked(a, 1)` /// * if there exists `b`, `n` such that `steps_between(&b, &a) == Some(n)`, /// it is safe to call `Step::backward_unchecked(a, m)` for any `m <= n`. /// /// For any `a` and `n`, where no overflow occurs: /// /// * `Step::backward_unchecked(a, n)` is equivalent to `Step::backward(a, n)` #[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")] unsafe fn backward_unchecked(start: Self, count: usize) -> Self { Step::backward(start, count) } } ``` Note that all of these are associated functions and not callable via method syntax; the calling syntax is always `Step::forward(start, n)`. This version of the trait additionally changes the stepping functions to talk their arguments by value. As opposed to previous attempts which provided a "step by one" method directly, this version of the trait only exposes "step by n". There are a few reasons for this: - `Range*`, the primary consumer of `Step`, assumes that the "step by n" operation is cheap. If a single step function is provided, it will be a lot more enticing to implement "step by n" as n repeated calls to "step by one". While this is not strictly incorrect, this behavior would be surprising for anyone used to using `Range<{primitive integer}>`. - With a trivial default impl, this can be easily added backwards-compatibly later. - The debug-wrapping "step by n" needs to exist for `RangeFrom` to be consistent between "step by n" and "step by one" operation. (Note: the behavior is not changed by this PR, but making the behavior consistent is made tenable by this PR.) Three "kinds" of step are provided: `_checked`, which returns an `Option` indicating attempted overflow; (unsuffixed), which provides "safe overflow" behavior (is allowed to panic, wrap, or saturate, depending on what is most convenient for a given type); and `_unchecked`, which is a version which assumes overflow does not happen. Review is appreciated to check that: - The invariants as described on the `Step` functions are enough to specify the "common sense" consistency for successor/predecessor. - Implementation of `Step` functions is correct in the face of overflow and the edges of representable integers. - Added tests of `Step` functions are asserting the correct behavior (and not just the implemented behavior).

@oli-obk

Miri interning: replace ICEs by proper errors Fixes rust-lang#71316 I also did some refactoring, as I kept being confused by all the parameters to `intern_shallow`, some of which have invalid combinations (such as a mutable const). So instead `InternMode` now contains all the information that is needed and invalid combinations are ruled out by the type system. Also I removed interpreter errors from interning. We already ignored almost all errors, and the `ValidationFailure` errors that we handled separately actually cannot ever happen here. The only interpreter failure that was actually reachable was the UB on dangling pointers -- and arguably, a dangling raw pointer is not UB, so the error was not even correct. It's just that the rest of the compiler does not like "dangling" `AllocId`. It should be possible to review the 3 commits separately. r? @oli-obk Cc @rust-lang/wg-const-eval

…rowth, r=oli-obk Be less aggressive with `DroplessArena`/`TypedArena` growth. `DroplessArena` and `TypedArena` use an aggressive growth strategy: the first chunk is 4 KiB, the second is 8 KiB, and it keeps on doubling indefinitely. DHAT profiles show that sometimes this results in large chunks (e.g. 16-128 MiB) that are barely filled. This commit changes things so that the doubling stops at 2 MiB. This is large enough that chunk allocations are still rare (you might get 100s instead of 10s of them) but avoids lots of unused space in the worst case. It makes the same change to `TypedArena`, too.

Update transitive dependency to work towards removing syn <1.0 dep This bumps a couple of transitive dependencies in hopes of eventually not transitively depending on syn <1.0 and friends. The only upstream changes that this is blocked on seems to be mattico/elasticlunr-rs#27 and rust-lang/mdBook#1210. While working on rust-lang#71875 I noticed we still use syn 0.15 here and there so this is a drive-by PR which aims to help with things a bit.

@oli-obk

…oli-obk rustc_driver: factor out computing the exit code In a recent Miri PR I [added a convenience wrapper](https://github.com/rust-lang/miri/pull/1405/files#diff-c3d602c5c8035a16699ce9c015bfeceaR125) around `catch_fatal_errors` and `run_compiler` that @oli-obk suggested I could upstream. However, after seeing what could be shared between `rustc_driver::main`, clippy and Miri, really the only thing I found is computing the exit code -- so that's what this PR does. What prevents using the Miri convenience function in `rustc_driver::main` and clippy is that they do extra work inside `catch_fatal_errors`, and while I could abstract that away, clippy actually *computes the callbacks* inside there, and I fond no good way to abstract that and thus gave up. Maybe the clippy thing could be moved out, I am not sure if it ever can actually raise a `FatalErrorMarker` -- someone more knowledgeable in clippy would have to do that.

RalfJung · 2020-05-15T06:42:23Z

@rustbot modify labels: +rollup
@bors r+ rollup=never p=5

bors · 2020-05-15T06:42:25Z

📌 Commit 7d01ffc has been approved by RalfJung

bors · 2020-05-15T06:43:02Z

⌛ Testing commit 7d01ffc with merge 7b798a2f49388d9d62c588223058d62a5312e9f5...

bors · 2020-05-15T09:04:46Z

💔 Test failed - checks-azure

RalfJung · 2020-05-15T09:09:35Z

Hm, an ICE on 32bit Windows...

thread 'rustc' panicked at 'assertion failed: self.ptr <= self.end', D:\a\1\s\src\libstd\macros.rs:13:23
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

No idea what could be causing that...

CAD97 and others added 26 commits April 8, 2020 02:11

Add inherent impls for unchecked math intrinsics

b70e7fd

Redesign the Step trait

2fcfd23

Adjust Step::forward_checked docs for large types

f34322d

Co-Authored-By: Nadrieril Feneanar <nadrieril@users.noreply.github.com>

Miri interning: replace ICEs by proper errors, make intern_shallow ty…

c400f75

…pe signature more precise

remove some dead code, and assert we do not swallow allocating errors

8e48a30

avoid raising interpreter errors from interning

ff39457

fmt

d3b2e1f

Typo

a06740c

Co-Authored-By: Oliver Scherer <github35764891676564198441@oli-obk.de>

rebase fallout

e73ee41

rustc_driver: factor out computing the exit code

23d880b

rustc_driver::main: more informative return type

51e466d

cargo update -p serde_derive

5e35493

cargo update -p failure_derive

403a9d0

cargo update -p pest_generator

8c6e568

cargo update -p derive-new

3bdaced

rustbook: Bump mdbook dependency

e26f35d

Fix the new capacity measurement in arenas.

9111d8b

For the given code paths, the amount of space used in the previous chunk is irrelevant. (This will almost never make a difference to behaviour, but it makes the code clearer.)

Improve comments in iter::Step

cef616b

Improve Step::forward/backward for optimization

90b1961

The previous definition did not optimize down to a single add operation, but this version does appear to.

improve step_integer_impls macro

d53068e

rustbot added the rollup A PR which is a rollup label May 15, 2020

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label May 15, 2020

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels May 15, 2020

Dylan-DPC-zz closed this May 15, 2020

This was referenced May 15, 2020

Rollup of 5 pull requests #72228

Closed

Rework the std::iter::Step trait #69659

Merged

RalfJung deleted the rollup-pe1gxkk branch May 15, 2020 11:53

This was referenced May 15, 2020

Be less aggressive with DroplessArena/TypedArena growth. #71872

Merged

Rollup of 6 pull requests #72229

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Rollup of 5 pull requests #72226

Rollup of 5 pull requests #72226

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Rollup of 5 pull requests #72226

Rollup of 5 pull requests #72226

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