simplify: port RefineType + GuardType identity to C (chunk 3)

Two new C handlers:
- simplify_refine_type_c: fully replaces C++ simplifyRefineType
- simplify_guard_type_identity_c: handles GuardType identity path
  (type already matches), falls through to C++ for TNoneType case

Author: SonicField

Python/jit/hir/simplify.cpp

@@ -2736,10 +2736,13 @@ Register* simplifyInstr(Env& env, const Instr* instr) {
       return static_cast<Register*>(simplify_check_c(instr));
     case Opcode::kCheckSequenceBounds:
       return simplifyCheckSequenceBounds(env, instr);
-    case Opcode::kGuardType:
+    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));
+    }
     case Opcode::kRefineType:
-      return simplifyRefineType(static_cast<const RefineType*>(instr));
+      return static_cast<Register*>(simplify_refine_type_c(instr));
     case Opcode::kCast:
       return simplifyCast(static_cast<const Cast*>(instr));
 

Python/jit/hir/simplify_c.c

@@ -46,6 +46,30 @@ void *simplify_check_c(const void *instr) {
     return NULL;
 }
 
+/* ---- simplifyRefineType ----
+ * If input already has the target type, RefineType is redundant. */
+void *simplify_refine_type_c(const void *instr) {
+    void *input = hir_c_get_operand(instr, 0);
+    HirType input_type = hir_register_type(input);
+    HirType target = ((const HirRefineType *)instr)->type;
+    if (hir_type_is_subtype(input_type, target)) {
+        return input;
+    }
+    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) {
+    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;
+    }
+    return NULL;
+}
+
 /* ---- simplifyIsTruthy (partial — CBool constant folding) ----
  * If input is a known CBool constant, replace with the constant directly. */
 void *simplify_is_truthy_cbool_c(SimplifyEnv *env, const void *instr) {

Python/jit/hir/simplify_c.h

@@ -27,6 +27,8 @@ 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);
 
 /* Env-using handlers */
 void *simplify_is_truthy_cbool_c(SimplifyEnv *env, const void *instr);