ZJIT: Detect built-in functions' attributes automatically

Author: st0012

zjit.c

@@ -331,6 +331,12 @@ rb_iseq_set_zjit_payload(const rb_iseq_t *iseq, void *payload)
     iseq->body->zjit_payload = payload;
 }
 
+unsigned int
+rb_zjit_get_iseq_body_builtin_attrs(const rb_iseq_t *iseq)
+{
+    return iseq->body->builtin_attrs;
+}
+
 void
 rb_zjit_print_exception(void)
 {

zjit/bindgen/src/main.rs

@@ -334,6 +334,7 @@ fn main() {
         .allowlist_function("rb_zjit_mark_executable")
         .allowlist_function("rb_zjit_mark_unused")
         .allowlist_function("rb_zjit_get_page_size")
+        .allowlist_function("rb_zjit_get_iseq_body_builtin_attrs")
         .allowlist_function("rb_zjit_iseq_builtin_attrs")
         .allowlist_function("rb_zjit_iseq_inspect")
         .allowlist_function("rb_zjit_iseq_insn_set")

zjit/src/cruby_bindings.inc.rs

@@ -67,7 +67,7 @@ fn annotate_c_method(props_map: &mut HashMap<*mut c_void, FnProperties>, class:
 }
 
 /// Look up a method and find its builtin function pointer by parsing its ISEQ
-fn annotate_builtin_method(props_map: &mut HashMap<*mut c_void, FnProperties>, class: VALUE, method_name: &'static str, props: FnProperties) {
+fn annotate_builtin_method(props_map: &mut HashMap<*mut c_void, FnProperties>, class: VALUE, method_name: &'static str, mut props: FnProperties) {
     unsafe {
         let method_id = rb_intern2(method_name.as_ptr().cast(), method_name.len().try_into().unwrap());
         let method = rb_method_entry_at(class, method_id);
@@ -93,6 +93,15 @@ fn annotate_builtin_method(props_map: &mut HashMap<*mut c_void, FnProperties>, c
                 method_name);
         }
 
+        // Check if the ISEQ has the BUILTIN_ATTR_LEAF attribute
+        let builtin_attrs = rb_zjit_get_iseq_body_builtin_attrs(iseq);
+        if (builtin_attrs & BUILTIN_ATTR_LEAF) != 0 {
+            // If the method is marked as leaf via Primitive.attr!, set leaf to true
+            props.leaf = true;
+            // Leaf methods don't trigger GC
+            props.no_gc = true;
+        }
+
         // Get the size of the ISEQ in instruction units
         let encoded_size = rb_iseq_encoded_size(iseq);
 
@@ -163,6 +172,7 @@ pub fn init() -> Annotations {
     annotate!(rb_mKernel, "nil?", types::FalseClass, no_gc, leaf, elidable);
 
     // Annotate builtin functions using the new method-based approach
+    // The leaf property will be automatically detected from Primitive.attr! :leaf in the Ruby code
     annotate_builtin!(rb_mKernel, "Float", types::Flonum);
     annotate_builtin!(rb_mKernel, "Integer", types::Integer);
     annotate_builtin!(rb_mKernel, "class", types::Class);