ZJIT: Profile nil? calls

This allows ZJIT to profile `nil?` calls and create type guards for
its receiver.

- Add `zjit_profile` to `opt_nil_p` insn
- Start profiling `opt_nil_p` calls
- Use `runtime_exact_ruby_class` instead of `exact_ruby_class` to determine
  the profiled receiver class

insns.def

@@ -996,6 +996,7 @@ opt_nil_p
 (CALL_DATA cd)
 (VALUE recv)
 (VALUE val)
+// attr bool zjit_profile = true;
 {
     val = vm_opt_nil_p(GET_ISEQ(), cd, recv);
 

zjit/src/cruby_bindings.inc.rs

@@ -683,18 +683,19 @@ pub const YARVINSN_trace_setlocal_WC_1: ruby_vminsn_type = 219;
 pub const YARVINSN_trace_putobject_INT2FIX_0_: ruby_vminsn_type = 220;
 pub const YARVINSN_trace_putobject_INT2FIX_1_: ruby_vminsn_type = 221;
 pub const YARVINSN_zjit_opt_send_without_block: ruby_vminsn_type = 222;
-pub const YARVINSN_zjit_opt_plus: ruby_vminsn_type = 223;
-pub const YARVINSN_zjit_opt_minus: ruby_vminsn_type = 224;
-pub const YARVINSN_zjit_opt_mult: ruby_vminsn_type = 225;
-pub const YARVINSN_zjit_opt_div: ruby_vminsn_type = 226;
-pub const YARVINSN_zjit_opt_mod: ruby_vminsn_type = 227;
-pub const YARVINSN_zjit_opt_eq: ruby_vminsn_type = 228;
-pub const YARVINSN_zjit_opt_neq: ruby_vminsn_type = 229;
-pub const YARVINSN_zjit_opt_lt: ruby_vminsn_type = 230;
-pub const YARVINSN_zjit_opt_le: ruby_vminsn_type = 231;
-pub const YARVINSN_zjit_opt_gt: ruby_vminsn_type = 232;
-pub const YARVINSN_zjit_opt_ge: ruby_vminsn_type = 233;
-pub const VM_INSTRUCTION_SIZE: ruby_vminsn_type = 234;
+pub const YARVINSN_zjit_opt_nil_p: ruby_vminsn_type = 223;
+pub const YARVINSN_zjit_opt_plus: ruby_vminsn_type = 224;
+pub const YARVINSN_zjit_opt_minus: ruby_vminsn_type = 225;
+pub const YARVINSN_zjit_opt_mult: ruby_vminsn_type = 226;
+pub const YARVINSN_zjit_opt_div: ruby_vminsn_type = 227;
+pub const YARVINSN_zjit_opt_mod: ruby_vminsn_type = 228;
+pub const YARVINSN_zjit_opt_eq: ruby_vminsn_type = 229;
+pub const YARVINSN_zjit_opt_neq: ruby_vminsn_type = 230;
+pub const YARVINSN_zjit_opt_lt: ruby_vminsn_type = 231;
+pub const YARVINSN_zjit_opt_le: ruby_vminsn_type = 232;
+pub const YARVINSN_zjit_opt_gt: ruby_vminsn_type = 233;
+pub const YARVINSN_zjit_opt_ge: ruby_vminsn_type = 234;
+pub const VM_INSTRUCTION_SIZE: ruby_vminsn_type = 235;
 pub type ruby_vminsn_type = u32;
 pub type rb_iseq_callback = ::std::option::Option<
     unsafe extern "C" fn(arg1: *const rb_iseq_t, arg2: *mut ::std::os::raw::c_void),

zjit/src/hir.rs

@@ -1547,7 +1547,7 @@ impl Function {
             } else {
                 let iseq_insn_idx = fun.frame_state(state).insn_idx;
                 let Some(recv_type) = fun.profiled_type_of_at(self_val, iseq_insn_idx) else { return Err(()) };
-                let Some(recv_class) = recv_type.exact_ruby_class() else { return Err(()) };
+                let Some(recv_class) = recv_type.runtime_exact_ruby_class() else { return Err(()) };
                 (recv_class, Some(recv_type.unspecialized()))
             };
 
@@ -6659,4 +6659,21 @@ mod opt_tests {
               Return v5
         "#]]);
     }
+
+    #[test]
+    fn test_guard_nil_for_nil_opt() {
+        eval("
+            def test(val) = val.nil?
+
+            test(nil)
+        ");
+        assert_optimized_method_hir("test", expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject):
+              PatchPoint MethodRedefined(NilClass@0x1000, nil?@0x1008)
+              v7:NilClassExact = GuardType v1, NilClassExact
+              v8:TrueClassExact = CCall nil?@0x1010, v7
+              Return v8
+        "#]]);
+    }
 }

zjit/src/profile.rs

@@ -51,6 +51,7 @@ pub extern "C" fn rb_zjit_profile_insn(opcode: ruby_vminsn_type, ec: EcPtr) {
 /// Profile a YARV instruction
 fn profile_insn(profiler: &mut Profiler, opcode: ruby_vminsn_type) {
     match opcode {
+        YARVINSN_opt_nil_p => profile_operands(profiler, 1),
         YARVINSN_opt_plus  => profile_operands(profiler, 2),
         YARVINSN_opt_minus => profile_operands(profiler, 2),
         YARVINSN_opt_mult  => profile_operands(profiler, 2),