Couple of changes to run rustc in miri

compiler/rustc_data_structures/src/stack.rs

@@ -17,6 +17,18 @@ const STACK_PER_RECURSION: usize = 16 * 1024 * 1024; // 16MB
 ///
 /// Should not be sprinkled around carelessly, as it causes a little bit of overhead.
 #[inline]
+#[cfg(not(miri))]
 pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
     stacker::maybe_grow(RED_ZONE, STACK_PER_RECURSION, f)
 }
+
+/// Grows the stack on demand to prevent stack overflow. Call this in strategic locations
+/// to "break up" recursive calls. E.g. almost any call to `visit_expr` or equivalent can benefit
+/// from this.
+///
+/// Should not be sprinkled around carelessly, as it causes a little bit of overhead.
+#[cfg(miri)]
+#[inline]
+pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
+    f()
+}