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.

Author: matthiaskrgr

src/intrinsics/mod.rs

@@ -391,32 +391,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.write_scalar(res, dest)?;
             }
 
-            #[rustfmt::skip]
-            | "fadd_algebraic"
-            | "fsub_algebraic"
-            | "fmul_algebraic"
-            | "fdiv_algebraic"
-            | "frem_algebraic"
-            => {
-                let [a, b] = check_intrinsic_arg_count(args)?;
-                let a = this.read_immediate(a)?;
-                let b = this.read_immediate(b)?;
-                let op = match intrinsic_name {
-                    "fadd_algebraic" => mir::BinOp::Add,
-                    "fsub_algebraic" => mir::BinOp::Sub,
-                    "fmul_algebraic" => mir::BinOp::Mul,
-                    "fdiv_algebraic" => mir::BinOp::Div,
-                    "frem_algebraic" => mir::BinOp::Rem,
-                    _ => bug!(),
-                };
-                let res = this.binary_op(op, &a, &b)?;
-                // `binary_op` already called `generate_nan` if needed.
-                // Apply a relative error of 4ULP to simulate non-deterministic precision loss
-                // due to optimizations.
-                let res = apply_random_float_error_to_imm(this, res, 2 /* log2(4) */)?;
-                this.write_immediate(*res, dest)?;
-            }
-
             #[rustfmt::skip]
             | "fadd_fast"
             | "fsub_fast"