`unchecked_{shl|shr}` should use `u32` as the RHS #103456

scottmcm · 2022-10-24T00:08:07Z

The other shift methods, such as https://doc.rust-lang.org/nightly/std/primitive.u64.html#method.checked_shr and https://doc.rust-lang.org/nightly/std/primitive.i16.html#method.wrapping_shl, use u32 for the shift amount. That's consistent with other things, like count_ones, which also always use u32 for a bit count, regardless of the size of the type.

This PR changes unchecked_shl and unchecked_shr to also use u32 for the shift amount (rather than Self).

cc #85122, the unchecked_math tracking issue

rust-highfive · 2022-10-24T00:08:10Z

r? @joshtriplett

(rust-highfive has picked a reviewer for you, use r? to override)

rustbot · 2022-10-24T00:08:10Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

scottmcm · 2022-10-24T00:10:00Z

src/test/codegen/unchecked_shifts.rs

+#[no_mangle]
+pub unsafe fn unchecked_shl_unsigned_same(a: u32, b: u32) -> u32 {
+    // CHECK-NOT: and i32
+    // CHECK: shl i32 %a, %b


annot: the LLVM instruction always gives poison by default for too-high shift amounts (https://llvm.org/docs/LangRef.html#shl-instruction), so no extra flags are expected in the IR.

scottmcm · 2022-10-24T00:11:06Z

library/core/src/num/int_macros.rs

@@ -1383,11 +1386,12 @@ macro_rules! int_impl {
        #[must_use = "this returns the result of the operation, \
                      without modifying the original"]
        #[inline(always)]
+        #[rustc_allow_const_fn_unstable(const_inherent_unchecked_arith)]


annot: this was previously using the intrinsic on stable, so the rustc_allow_const_fn_unstable isn't exposing anything new to stable here.

scottmcm · 2022-10-24T00:12:08Z

library/core/src/num/int_macros.rs

            // SAFETY: the caller must uphold the safety contract for
            // `unchecked_shl`.
-            unsafe { intrinsics::unchecked_shl(self, rhs) }
+            // Any legal shift amount is losslessly representable in the self type.
+            unsafe { intrinsics::unchecked_shl(self, rhs.try_into().ok().unwrap_unchecked()) }


annot: the .ok() looks silly here, but Result::unwrap_unchecked isn't const, whereas Option::unwrap_unchecked is const.

scottmcm · 2022-11-15T03:11:38Z

Hi libs-api! I'm nominating this one to get a 👍/👎 on the signature change, in hopes of then being able to move it to a less-busy reviewer once the API decision is made.

m-ou-se · 2022-11-15T11:48:51Z

@bors r+

bors · 2022-11-15T11:48:53Z

📌 Commit 3b16c04 has been approved by m-ou-se

It is now in the queue for this repository.

…-ou-se `unchecked_{shl|shr}` should use `u32` as the RHS The other shift methods, such as https://doc.rust-lang.org/nightly/std/primitive.u64.html#method.checked_shr and https://doc.rust-lang.org/nightly/std/primitive.i16.html#method.wrapping_shl, use `u32` for the shift amount. That's consistent with other things, like `count_ones`, which also always use `u32` for a bit count, regardless of the size of the type. This PR changes `unchecked_shl` and `unchecked_shr` to also use `u32` for the shift amount (rather than Self). cc rust-lang#85122, the `unchecked_math` tracking issue

scottmcm · 2022-11-16T07:22:18Z

@bors rollup=iffy (failed in a rollup once, but with the update that config worked in CI)
@bors r-

Failed in rollup https://github.com/rust-lang-ci/rust/actions/runs/3477142652/jobs/5813017785

scottmcm · 2022-11-17T00:45:13Z

Did the test-in-CI trick, and it doesn't fail that config any more: https://github.com/rust-lang/rust/actions/runs/3484161910/jobs/5828408349

@bors r+

bors · 2022-11-17T00:45:14Z

📌 Commit 9d4b1f9 has been approved by scottmcm

It is now in the queue for this repository.

bors · 2022-11-17T00:45:15Z

🌲 The tree is currently closed for pull requests below priority 1. This pull request will be tested once the tree is reopened.

…cottmcm `unchecked_{shl|shr}` should use `u32` as the RHS The other shift methods, such as https://doc.rust-lang.org/nightly/std/primitive.u64.html#method.checked_shr and https://doc.rust-lang.org/nightly/std/primitive.i16.html#method.wrapping_shl, use `u32` for the shift amount. That's consistent with other things, like `count_ones`, which also always use `u32` for a bit count, regardless of the size of the type. This PR changes `unchecked_shl` and `unchecked_shr` to also use `u32` for the shift amount (rather than Self). cc rust-lang#85122, the `unchecked_math` tracking issue

…earth Rollup of 8 pull requests Successful merges: - rust-lang#102977 (remove HRTB from `[T]::is_sorted_by{,_key}`) - rust-lang#103378 (Fix mod_inv termination for the last iteration) - rust-lang#103456 (`unchecked_{shl|shr}` should use `u32` as the RHS) - rust-lang#103701 (Simplify some pointer method implementations) - rust-lang#104047 (Diagnostics `icu4x` based list formatting.) - rust-lang#104338 (Enforce that `dyn*` coercions are actually pointer-sized) - rust-lang#104498 (Edit docs for `rustc_errors::Handler::stash_diagnostic`) - rust-lang#104556 (rustdoc: use `code-header` class to format enum variants) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

rust-highfive assigned joshtriplett Oct 24, 2022

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Oct 24, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 24, 2022

scottmcm commented Oct 24, 2022

View reviewed changes

unchecked_{shl|shr} should use u32 as the RHS

3b16c04

scottmcm force-pushed the fix-unchecked-shifts branch from debadbc to 3b16c04 Compare October 24, 2022 00:33

scottmcm mentioned this pull request Oct 24, 2022

Tracking Issue for inherent unchecked integer methods #85122

Open

20 tasks

scottmcm added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. and removed T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Oct 25, 2022

scottmcm added the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Nov 15, 2022

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 15, 2022

m-ou-se removed the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Nov 15, 2022

scottmcm assigned m-ou-se and unassigned joshtriplett Nov 16, 2022

Dylan-DPC mentioned this pull request Nov 16, 2022

Rollup of 9 pull requests #104479

Closed

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 16, 2022

Ignore the unchecked-shifts codegen test in debug-assertions builds

9d4b1f9

rustbot added the A-testsuite Area: The testsuite used to check the correctness of rustc label Nov 17, 2022

rustbot added the T-infra Relevant to the infrastructure team, which will review and decide on the PR/issue. label Nov 17, 2022

scottmcm force-pushed the fix-unchecked-shifts branch 2 times, most recently from 1e783ac to 9d4b1f9 Compare November 17, 2022 00:44

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 17, 2022

Manishearth mentioned this pull request Nov 18, 2022

Rollup of 9 pull requests #104585

Closed

This was referenced Nov 18, 2022

Rollup of 8 pull requests #104589

Closed

Rollup of 8 pull requests #104591

Merged

bors merged commit e230115 into rust-lang:master Nov 19, 2022

rustbot added this to the 1.67.0 milestone Nov 19, 2022

scottmcm deleted the fix-unchecked-shifts branch November 19, 2022 03:31

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

`unchecked_{shl|shr}` should use `u32` as the RHS #103456

`unchecked_{shl|shr}` should use `u32` as the RHS #103456

scottmcm commented Oct 24, 2022

rust-highfive commented Oct 24, 2022

rustbot commented Oct 24, 2022

scottmcm Oct 24, 2022

scottmcm Oct 24, 2022

scottmcm Oct 24, 2022

scottmcm commented Nov 15, 2022

m-ou-se commented Nov 15, 2022

bors commented Nov 15, 2022

scottmcm commented Nov 16, 2022 •

edited

Loading

scottmcm commented Nov 17, 2022

bors commented Nov 17, 2022

bors commented Nov 17, 2022

unchecked_{shl|shr} should use u32 as the RHS #103456

unchecked_{shl|shr} should use u32 as the RHS #103456

Conversation

scottmcm commented Oct 24, 2022

rust-highfive commented Oct 24, 2022

rustbot commented Oct 24, 2022

scottmcm Oct 24, 2022

Choose a reason for hiding this comment

scottmcm Oct 24, 2022

Choose a reason for hiding this comment

scottmcm Oct 24, 2022

Choose a reason for hiding this comment

scottmcm commented Nov 15, 2022

m-ou-se commented Nov 15, 2022

bors commented Nov 15, 2022

scottmcm commented Nov 16, 2022 • edited Loading

scottmcm commented Nov 17, 2022

bors commented Nov 17, 2022

bors commented Nov 17, 2022

`unchecked_{shl|shr}` should use `u32` as the RHS #103456

`unchecked_{shl|shr}` should use `u32` as the RHS #103456

scottmcm commented Nov 16, 2022 •

edited

Loading