YJIT: Skip pushing a frame for Hash#empty? (#9875)

hash.c

@@ -3015,7 +3015,7 @@ rb_hash_size_num(VALUE hash)
  *    {foo: 0, bar: 1, baz: 2}.empty? # => false
  */
 
-static VALUE
+VALUE
 rb_hash_empty_p(VALUE hash)
 {
     return RBOOL(RHASH_EMPTY_P(hash));

yjit/src/codegen.rs

@@ -5499,6 +5499,27 @@ fn jit_rb_ary_push(
     true
 }
 
+// Just a leaf method, but not using `Primitive.attr! :leaf` since BOP methods can't use it.
+fn jit_rb_hash_empty_p(
+    _jit: &mut JITState,
+    asm: &mut Assembler,
+    _ocb: &mut OutlinedCb,
+    _ci: *const rb_callinfo,
+    _cme: *const rb_callable_method_entry_t,
+    _block: Option<BlockHandler>,
+    _argc: i32,
+    _known_recv_class: *const VALUE,
+) -> bool {
+    asm_comment!(asm, "Hash#empty?");
+
+    let hash_opnd = asm.stack_pop(1);
+    let ret = asm.ccall(rb_hash_empty_p as *const u8, vec![hash_opnd]);
+
+    let ret_opnd = asm.stack_push(Type::UnknownImm);
+    asm.mov(ret_opnd, ret);
+    true
+}
+
 fn jit_obj_respond_to(
     jit: &mut JITState,
     asm: &mut Assembler,
@@ -9360,6 +9381,8 @@ pub fn yjit_reg_method_codegen_fns() {
         yjit_reg_method(rb_cArray, "size", jit_rb_ary_length);
         yjit_reg_method(rb_cArray, "<<", jit_rb_ary_push);
 
+        yjit_reg_method(rb_cHash, "empty?", jit_rb_hash_empty_p);
+
         yjit_reg_method(rb_mKernel, "respond_to?", jit_obj_respond_to);
         yjit_reg_method(rb_mKernel, "block_given?", jit_rb_f_block_given_p);
 

yjit/src/cruby.rs

@@ -107,11 +107,12 @@ pub use autogened::*;
 // TODO: For #defines that affect memory layout, we need to check for them
 // on build and fail if they're wrong. e.g. USE_FLONUM *must* be true.
 
-// These are functions we expose from vm_insnhelper.c, not in any header.
+// These are functions we expose from C files, not in any header.
 // Parsing it would result in a lot of duplicate definitions.
 // Use bindgen for functions that are defined in headers or in yjit.c.
 #[cfg_attr(test, allow(unused))] // We don't link against C code when testing
 extern "C" {
+    pub fn rb_hash_empty_p(hash: VALUE) -> VALUE;
     pub fn rb_vm_splat_array(flag: VALUE, ary: VALUE) -> VALUE;
     pub fn rb_vm_concat_array(ary1: VALUE, ary2st: VALUE) -> VALUE;
     pub fn rb_vm_concat_to_array(ary1: VALUE, ary2st: VALUE) -> VALUE;