rustc_data_structures/
stack.rs

1// This is the amount of bytes that need to be left on the stack before increasing the size.
2// It must be at least as large as the stack required by any code that does not call
3// `ensure_sufficient_stack`.
4const RED_ZONE: usize = 100 * 1024; // 100k
5
6// Only the first stack that is pushed, grows exponentially (2^n * STACK_PER_RECURSION) from then
7// on. This flag has performance relevant characteristics. Don't set it too high.
8#[cfg(not(target_os = "aix"))]
9const STACK_PER_RECURSION: usize = 1024 * 1024; // 1MB
10// LLVM for AIX doesn't feature TCO, increase recursion size for workaround.
11#[cfg(target_os = "aix")]
12const STACK_PER_RECURSION: usize = 16 * 1024 * 1024; // 16MB
13
14/// Grows the stack on demand to prevent stack overflow. Call this in strategic locations
15/// to "break up" recursive calls. E.g. almost any call to `visit_expr` or equivalent can benefit
16/// from this.
17///
18/// Should not be sprinkled around carelessly, as it causes a little bit of overhead.
19#[inline]
20pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
21    stacker::maybe_grow(RED_ZONE, STACK_PER_RECURSION, f)
22}