document rounding behavior of rint/nearbyint for ties #119656
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I opened llvm/llvm-project#77191 to clarify the docs on the LLVM side. |
| /// Returns the nearest integer to an `f32`. Changing the rounding mode is not possible in Rust, | ||
| /// so this rounds half-way cases to the number with an even least significant digit. | ||
| /// | ||
| /// May raise an inexact floating-point exception if the argument is not an integer. |
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This exception isn't mentioned in the round_ties_even docs -- is this something we should be guarding against somehow? Is raising an exception UB, or does that just (guaranteed) abort the program? Feels... unhelpful to have a rounding function only allow exactly integer inputs.
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This is an FP exception. All it does is set a bit in some register that Rust code is not allowed to read.
One can set up the FP environment to turn these exceptions into traps, but Rust doesn't permit that.
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…crum document rounding behavior of rint/nearbyint for ties It's not possible to change the rounding mode in Rust, so these intrinsics will always behave like `roundeven`.
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…iaskrgr Rollup of 3 pull requests Successful merges: - rust-lang#119654 (bump bootstrap dependencies) - rust-lang#119656 (document rounding behavior of rint/nearbyint for ties) - rust-lang#119657 (Fix typo in docs for slice::split_once, slice::rsplit_once) r? `@ghost` `@rustbot` modify labels: rollup
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…mpiler-errors Rollup of 6 pull requests Successful merges: - rust-lang#119252 (rustc_mir_transform: Enforce `rustc::potential_query_instability` lint) - rust-lang#119548 (Use the current target instead of iterating over all targets) - rust-lang#119656 (document rounding behavior of rint/nearbyint for ties) - rust-lang#119657 (Fix typo in docs for slice::split_once, slice::rsplit_once) - rust-lang#119666 (Populate `yield` and `resume` types in MIR body while body is being initialized) - rust-lang#119679 (Ask for rustc version in diagnostic reports, remind users to update their toolchain) r? `@ghost` `@rustbot` modify labels: rollup
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…mpiler-errors Rollup of 6 pull requests Successful merges: - rust-lang#119252 (rustc_mir_transform: Enforce `rustc::potential_query_instability` lint) - rust-lang#119548 (Use the current target instead of iterating over all targets) - rust-lang#119656 (document rounding behavior of rint/nearbyint for ties) - rust-lang#119657 (Fix typo in docs for slice::split_once, slice::rsplit_once) - rust-lang#119666 (Populate `yield` and `resume` types in MIR body while body is being initialized) - rust-lang#119679 (Ask for rustc version in diagnostic reports, remind users to update their toolchain) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#119656 - RalfJung:round-docs, r=Mark-Simulacrum document rounding behavior of rint/nearbyint for ties It's not possible to change the rounding mode in Rust, so these intrinsics will always behave like `roundeven`.
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It's not possible to change the rounding mode in Rust, so these intrinsics will always behave like
roundeven.