[Migrated] Large array variable initialization (`let arr = [0; 32 * 1024];`) compiles very slowly.

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/1132
Old labels: t: bug
Originally creatd by pyranota on 2024-02-11T13:28:58Z

EDIT(@eddyb): while there are reasons to avoid such arrays, the slowdown is the immediate Rust-GPU bug - I've left unchanged the original text, but used strikethrough for parts that don't apply, IMO.

User should not be able to create large sized arrays in rust-gpu shaders.
Stack is limited, and large sized data-structures should be moved in buffers.
Plus it makes compilation incredibly slow (I assume this syntax [0; SIZE] translates to spirv's [0, 0, 0, 0, 0, ... SIZE])

Expected Behaviour

spirv-builder should throw an error, when user creates large array in stack

Example & Steps To Reproduce

1. Setup basic rust-gpu shader
2. let arr = [0; 32 * 1024];
3. cargo build

System Info

• Rust: rustc 1.75.0 (82e1608df 2023-12-21)
• OS: Pop!_OS
• GPU: nvidia 1060
• SPIR-V: SPIRV-Tools v2022.2-dev unknown hash, 2022-02-16T16:37:15

この issue にはソースファイルもテストも指定されていないため、まず let arr = [0; 32 * 1024]; を使った最小限の rust-gpu shader reproducer から始め、次に cargo build を実行して、遅延の原因となっているコンパイルパスを追跡します。この大きな配列初期化子によってコンパイルが極端に遅くならなくなり、関連するテストの場所を特定できる場合は回帰テストも追加されれば完了です。