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move per-target NaN info into a table

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This commit is contained in:
Ralf Jung 2024-08-26 17:16:53 +02:00
parent fe2975076f
commit 53d4544628
1 changed files with 14 additions and 7 deletions
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21
library/core/src/primitive_docs.rs
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@ -1250,13 +1250,8 @@ mod prim_f16 {}
/// possible with a signaling NaN (the all-0 significand encodes an infinity) so unchanged NaN /// possible with a signaling NaN (the all-0 significand encodes an infinity) so unchanged NaN
/// propagation cannot occur with some inputs. /// propagation cannot occur with some inputs.
/// - **Target-specific NaN**: The quiet bit is set and the payload is picked from a target-specific /// - **Target-specific NaN**: The quiet bit is set and the payload is picked from a target-specific
/// set of "extra" possible NaN payloads. The set can depend on the input operand values. This set /// set of "extra" possible NaN payloads. The set can depend on the input operand values.
/// is empty on x86, ARM, and RISC-V (32bit and 64bit), but can be non-empty on other /// See the table below for the concrete NaNs this set contains on various targets.
/// architectures. Targets where this set is non-empty should document this in a suitable
/// location, e.g. their platform support page. (For instance, on wasm, if any input NaN does not
/// have the preferred all-zero payload or any input NaN is an SNaN, then this set contains all
/// possible payloads; otherwise, it is empty. On SPARC, this set consists of the all-one
/// payload.)
/// ///
/// In particular, if all input NaNs are quiet (or if there are no input NaNs), then the output NaN /// In particular, if all input NaNs are quiet (or if there are no input NaNs), then the output NaN
/// is definitely quiet. Signaling NaN outputs can only occur if they are provided as an input /// is definitely quiet. Signaling NaN outputs can only occur if they are provided as an input
@ -1282,6 +1277,18 @@ mod prim_f16 {}
/// guarantee is made about which of the NaN bit patterns described above will be returned. The /// guarantee is made about which of the NaN bit patterns described above will be returned. The
/// result does not have to match what happens when executing the same code at runtime, and the /// result does not have to match what happens when executing the same code at runtime, and the
/// result can vary depending on factors such as compiler version and flags. /// result can vary depending on factors such as compiler version and flags.
///
/// ### Target-specific "extra" NaN values
// FIXME: Is there a better place to put this?
///
/// | `target_arch` | Extra payloads possible on this platform |
/// |---------------|---------|
/// | `x86`, `x86_64`, `arm`, `aarch64`, `riscv32`, `riscv64` | None |
/// | `sparc`, `sparc64` | The all-one payload |
/// | `wasm32`, `wasm64` | If all input NaNs are quiet with all-zero payload: None.<br> Otherwise: all possible payloads. |
///
/// For targets not in this table, all payloads are possible.
#[stable(feature = "rust1", since = "1.0.0")] #[stable(feature = "rust1", since = "1.0.0")]
mod prim_f32 {} mod prim_f32 {}