================
@@ -4032,6 +4032,49 @@ callee is unavailable or if the callee has the
``noinline`` attribute.
}];
}
+def FlattenDepthDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+The ``flatten_depth`` attribute provides a hint to the inliner to aggressively
+inline calls within the attributed function and their transitive callees up to
+a specified depth in the call tree.
+
+This attribute takes a single unsigned integer argument representing the
+requested depth of inlining. For example, ``__attribute__((flatten_depth(3)))``
+requests that calls within the function be inlined (depth 1), then calls within
+those inlined functions (depth 2), and then calls within those functions
(depth 3).
+
+**Important**: This attribute is a requested depth hint, not a hard constraint.
+The actual inlining behavior is subject to several considerations:
+
+- **Interaction with other attributes**: Functions marked with
``always_inline``
+ will be inlined even if they exceed the requested depth. Similarly, functions
+ marked with ``noinline`` will not be inlined regardless of the requested
depth.
+
+- **Cost model decisions**: The compiler's inlining cost model may choose to
+ inline functions beyond the requested depth if doing so is deemed beneficial
+ (e.g., trivial wrapper functions or obvious optimization opportunities). This
+ prevents the attribute from becoming a footgun that blocks beneficial
optimizations.
----------------
erichkeane wrote:
```suggestion
prevents the attribute from blocking beneficial optimizations.
```
https://github.com/llvm/llvm-project/pull/165777
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