simplify: fully port GuardType to C (identity + TNoneType→GuardIs)

Replaces partial identity-only C handler with full implementation.
If input already has target type → return input (identity).
If target is TNoneType → emit GuardIs(Py_None) via hir_c_create_guard_is.
No C++ fallback needed — all paths covered.

Author: SonicField

Python/jit/hir/simplify.cpp

@@ -2741,9 +2741,10 @@ Register* simplifyInstr(Env& env, const Instr* instr) {
       return r;
     }
     case Opcode::kGuardType: {
-      auto *r = static_cast<Register*>(simplify_guard_type_identity_c(instr));
-      if (r) return r;
-      return simplifyGuardType(env, static_cast<const GuardType*>(instr));
+      SimplifyEnv cenv = make_c_env();
+      auto *r = static_cast<Register*>(simplify_guard_type_c(&cenv, instr));
+      sync_c_env(cenv);
+      return r;
     }
     case Opcode::kRefineType:
       return static_cast<Register*>(simplify_refine_type_c(instr));

Python/jit/hir/simplify_c.c

@@ -65,15 +65,22 @@ void *simplify_refine_type_c(const void *instr) {
     return NULL;
 }
 
-/* ---- simplifyGuardType (partial — type-already-matches path) ----
- * If input already has the guarded type, GuardType is redundant. */
-void *simplify_guard_type_identity_c(const void *instr) {
+/* ---- simplifyGuardType ----
+ * If input already has the guarded type, redundant.
+ * If target is NoneType, convert to GuardIs(Py_None). */
+void *simplify_guard_type_c(SimplifyEnv *env, const void *instr) {
     void *input = hir_c_get_operand(instr, 0);
     HirType input_type = hir_register_type(input);
     HirType target = hir_c_guard_type_target(instr);
     if (hir_type_is_subtype(input_type, target)) {
         return input;
     }
+    HirType t_none = HIR_TYPE_NONETYPE;
+    if (hir_type_equal(&target, &t_none)) {
+        extern void *hir_c_create_guard_is(void *func, void *target_obj, void *src);
+        void *guard = hir_c_create_guard_is(env->func, Py_None, input);
+        return simplify_env_emit(env, guard);
+    }
     return NULL;
 }
 

Python/jit/hir/simplify_c.h

@@ -28,7 +28,7 @@ void *simplify_env_emit_use_type(SimplifyEnv *env, void *val, HirType type);
 /* Env-free handlers (return existing register or NULL) */
 void *simplify_check_c(const void *instr);
 void *simplify_refine_type_c(const void *instr);
-void *simplify_guard_type_identity_c(const void *instr);
+void *simplify_guard_type_c(SimplifyEnv *env, const void *instr);
 void *simplify_primitive_compare_box_true_c(const void *instr);
 void *simplify_unbox_box_c(const void *instr);
 void *simplify_cond_branch_check_type_c(SimplifyEnv *env, const void *instr);