[Migrated] GEP not implemented for type struct [_; 0]

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/1075
Old labels: t: bug
Originally creatd by kevinboulain on 2023-06-16T09:49:20Z

Expected Behaviour

This compiles fine with rustc (I guess this bit is probably eliminated?).

Example & Steps To Reproduce

I was using const generic parameters to determine the length of some arrays. At some point, a base case ended up declaring a zero-length array, like so:

#![cfg_attr(target_arch = "spirv", no_std)]
use spirv_std::spirv;

fn example<const LENGTH: usize>() {
    let mut array = [0; LENGTH];
    for i in 0..array.len() {
        array[i] += i;
    }
}

#[spirv(compute(threads(1, 1, 1)))]
pub fn compute() {
    example::<0>();
}

Resulting in:

error: GEP not implemented for type struct [usize; 0] {  }
 --> examples/shaders/compute-shader/src/lib.rs:7:9
  |
7 |         array[i] += i;
  |         ^^^^^^^^^^^^^

System Info

• rustc: 1.71.0-nightly (1a5f8bce7 2023-05-26)
• rust-gpu: b2e5eb7

Reproduce the failure from examples/shaders/compute-shader/src/lib.rs using the const-generic example with LENGTH = 0. Start by tracing the reported GEP handling for the zero-length array type, and consider the issue done when the example compiles without the “GEP not implemented” error while preserving the existing nonzero-length behavior.