Rust Error E0075: Applying SIMD attribute to empty tuple struct

Understanding Rust Error E0075

Rust Error E0075 occurs when the #[simd] attribute is applied to an empty tuple struct. The #[simd] attribute, which stands for Single Instruction Multiple Data, defines a SIMD-vector, allowing operations to be performed on multiple data points simultaneously. However, to utilize SIMD operations, there must be values to operate upon. Applying the #[simd] attribute to an empty tuple structure is not valid and results in Rust Error E0075.

Erroneous code example:

#![allow(unused)]
#![feature(repr_simd)]

fn main() {
    #[repr(simd)]
    struct Bad; // error!
}

How to fix Rust Error E0075

To fix Rust Error E0075, ensure that the tuple struct is not empty. The struct must contain at least one element for valid SIMD operations. Here's a corrected version of the previous erroneous code example:

Fixed example:

#![allow(unused)]
#![feature(repr_simd)]

fn main() {
    #[repr(simd)]
    struct Good(u32); // ok!
}

In the fixed example, the tuple struct Good now contains an element of type u32, making it valid for SIMD operations with the #[simd] attribute.

Correct usage of SIMD in Rust

Now that you know how to fix Rust Error E0075, it is essential to understand how to correctly use SIMD in Rust. Here is an example illustrating the correct usage of SIMD:

Example:

#![allow(unused)]
#![feature(repr_simd)]
#[repr(simd)]
struct MySIMDVector(u32, u32, u32, u32);

fn main() {
    let vec1 = MySIMDVector(1, 2, 3, 4);
    let vec2 = MySIMDVector(5, 6, 7, 8);
    // Perform SIMD operations on vec1 and vec2
}

In this example, MySIMDVector is a valid SIMD-enabled tuple struct containing four u32 elements. Two instances of MySIMDVector (vec1 and vec2) are created, ready for SIMD operations.