Rollup merge of #140172 - bjoernager:const-float-algebraic, r=RalfJung
Make algebraic functions into `const fn` items.
Tracking issue: #136469
This PR makes the algebraic intrinsics and the unstable, algebraic functions of `f16`, `f32`, `f64`, and `f128` into `const fn` items:
```rust
impl f16 {
pub const fn algebraic_add(self, rhs: f16) -> f16;
pub const fn algebraic_sub(self, rhs: f16) -> f16;
pub const fn algebraic_mul(self, rhs: f16) -> f16;
pub const fn algebraic_div(self, rhs: f16) -> f16;
pub const fn algebraic_rem(self, rhs: f16) -> f16;
}
impl f32 {
pub const fn algebraic_add(self, rhs: f32) -> f32;
pub const fn algebraic_sub(self, rhs: f32) -> f32;
pub const fn algebraic_mul(self, rhs: f32) -> f32;
pub const fn algebraic_div(self, rhs: f32) -> f32;
pub const fn algebraic_rem(self, rhs: f32) -> f32;
}
impl f64 {
pub const fn algebraic_add(self, rhs: f64) -> f64;
pub const fn algebraic_sub(self, rhs: f64) -> f64;
pub const fn algebraic_mul(self, rhs: f64) -> f64;
pub const fn algebraic_div(self, rhs: f64) -> f64;
pub const fn algebraic_rem(self, rhs: f64) -> f64;
}
impl f128 {
pub const fn algebraic_add(self, rhs: f128) -> f128;
pub const fn algebraic_sub(self, rhs: f128) -> f128;
pub const fn algebraic_mul(self, rhs: f128) -> f128;
pub const fn algebraic_div(self, rhs: f128) -> f128;
pub const fn algebraic_rem(self, rhs: f128) -> f128;
}
// core::intrinsics
pub const fn fadd_algebraic<T: Copy>(a: T, b: T) -> T;
pub const fn fsub_algebraic<T: Copy>(a: T, b: T) -> T;
pub const fn fmul_algebraic<T: Copy>(a: T, b: T) -> T;
pub const fn fdiv_algebraic<T: Copy>(a: T, b: T) -> T;
pub const fn frem_algebraic<T: Copy>(a: T, b: T) -> T;
```
This PR does not preserve the initial behaviour of these functions yielding non-deterministic output under Miri; it is most likely desired to reimplement this behaviour at some point.
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