core: implement bool::select_unpredictable

[joboet]

Tracking issue: #133962
ACP: rust-lang/libs-team#468

[rustbot]

r? @tgross35

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[rustbot]

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @rust-lang/wg-const-eval

[the8472]

tests/codegen/intrinsics/select_unpredictable.rs could be updated to test the public method, since that's the one most people will care about.

[tgross35]

tests/codegen/intrinsics/select_unpredictable.rs could be updated to test the public method, since that's the one most people will care about.

+1, the usage at

rust/library/core/src/slice/mod.rs

Line 2838 in cdeddae

base = select_unpredictable(cmp == Greater, base, mid);

could also be updated.

Docs and API lgtm, r=me with the above.

[joboet]

tests/codegen/intrinsics/select_unpredictable.rs could be updated to test the public method, since that's the one most people will care about.

I'm a bit hesitant about this since other instrinsics tests don't test the public variant either...

[the8472]

At least transmute-niched.rs does, but perhaps that one is misplaced.

Another option is to test both the intrinsic and the public method.

[tgross35]

Since we don't test public versions of the other intrinsics, I suppose this is also fine without it. Though it seems there probably isn't any specific reason they don't exist, so it probably wouldn't hurt to have both if you are up for extending the existing tests.

[tgross35]

@joboet this just needs the tests extended, at your discretion.

@rustbot author

[joboet]

I've added a new codegen test, adding the tests in the same file resulted in the functions being merged. Iirc there is a codegen flag to disable that, but this seemed cleaner.

@bors r=@tgross35

[bors]

📌 Commit 8f3aa35 has been approved by tgross35

It is now in the queue for this repository.

[the8472]

Iirc there is a codegen flag to disable that, but this seemed cleaner.

yes, -Zmerge-functions=disabled. And the benefit of using that is that we have fewer test files. Adding another test has much lower compile overhead than adding another file.

[bors]

⌛ Testing commit 8f3aa35 with merge f17cf74...