W27c python#1: emitSetupWithCommon → C body + bridge stub

Helper for emitSetupWith + emitBeforeWith. Per W27c Step A scope.

C body: hir_builder_emit_setup_with_common_c (~45 lines). Pops manager,
allocates enter+exit, emits load_attr_special_reg for both, pushes exit,
allocates enter_result, emits vectorcall_reg with CallFlags::None=0u,
sets enter as operand 0, sets frame state, emits.

PY_VERSION_HEX conditional (_Py_Identifier vs PyObject*) folded into C++
stub: ids are passed as opaque void* downward. is_async drives error
message text selection.

NEW BRIDGE: hir_builder_emit_setup_with_common_c — out-param returns
enter_result via void**.

C primitives used: hir_c_create_load_attr_special_reg + hir_c_create_vectorcall_reg
+ hir_c_set_operand + hir_deopt_set_frame_state + hir_builder_temps_alloc_stack
(all existing).

C++ HIRBuilder::emitSetupWithCommon → 6-line bridge stub returning
Register* via cast of out-param.

Verification: cmake --build target jit/phoenix_jit clean (BUILD_EXIT=0).
This is the chain-dep root for W27c python#2 (SetupWith) + python#3 (BeforeWith).

Author: SonicField

Python/jit/hir/builder.cpp

@@ -4531,6 +4531,10 @@ void HIRBuilder::emitGetANext(TranslationContext& tc) {
       static_cast<void*>(&tc), static_cast<void*>(current_func_));
 }
 
+extern "C" void hir_builder_emit_setup_with_common_c(
+    void *tc, void *builder, void *enter_id, void *exit_id,
+    int is_async, void **out_enter_result);
+
 Register* HIRBuilder::emitSetupWithCommon(
     TranslationContext& tc,
 #if PY_VERSION_HEX < 0x030C0000
@@ -4541,38 +4545,11 @@ Register* HIRBuilder::emitSetupWithCommon(
     PyObject* exit_id,
 #endif
     bool is_async) {
-  // Load the enter and exit attributes from the manager, push exit, and return
-  // the result of calling enter().
-  PhxPtrArray& stack = tc.frame.stack;
-  Register* manager = static_cast<Register*>(phx_ptr_arr_pop(&stack));
-  Register* enter = temps_.AllocateStack();
-  Register* exit = temps_.AllocateStack();
-  tc.emitLoadAttrSpecial(
-      enter,
-      manager,
-      enter_id,
-      is_async
-          ? "'%.200s' object does not support the asynchronous context manager "
-            "protocol"
-          : "'%.200s' object does not support the context manager protocol",
-      tc.frame);
-  tc.emitLoadAttrSpecial(
-      exit,
-      manager,
-      exit_id,
-      is_async
-          ? "'%.200s' object does not support the asynchronous context manager "
-            "protocol (missed __aexit__ method)"
-          : "'%.200s' object does not support the context manager protocol "
-            "(missed __exit__ method)",
-      tc.frame);
-  phx_ptr_arr_push(&stack, exit);
-
-  Register* enter_result = temps_.AllocateStack();
-  auto call = tc.emitVectorCall(1, enter_result, CallFlags::None);
-  call->setFrameState(tc.frame);
-  call->SetOperand(0, enter);
-  return enter_result;
+  void *enter_result = nullptr;
+  hir_builder_emit_setup_with_common_c(
+      &tc, this, (void*)enter_id, (void*)exit_id, is_async ? 1 : 0,
+      &enter_result);
+  return static_cast<Register*>(enter_result);
 }
 
 void HIRBuilder::emitBeforeWith(

Python/jit/hir/builder_emit_c.c

@@ -4084,4 +4084,47 @@ void hir_builder_emit_primitive_load_const_c(
     (void)func;  /* unused; tc owns the emission */
 }
 
+/* W27c #1: emitSetupWithCommon — helper for emitSetupWith + emitBeforeWith.
+ * Mirrors C++ HIRBuilder::emitSetupWithCommon @ builder.cpp:4534.
+ *
+ * Loads __enter__ + __exit__ via emitLoadAttrSpecial, pushes exit, emits
+ * VectorCall(enter), returns enter_result via out-param. PY_VERSION_HEX
+ * conditional (_Py_Identifier vs PyObject*) folded in C++ stub: ids are
+ * passed as opaque void*. is_async selects the error message text. */
+void hir_builder_emit_setup_with_common_c(
+        PhxTranslationContext *tc,
+        void *builder,
+        void *enter_id,
+        void *exit_id,
+        int is_async,
+        void **out_enter_result) {
+    void *manager = phx_ptr_arr_pop(&tc->frame.stack);
+    void *enter = hir_builder_temps_alloc_stack(builder);
+    void *exit = hir_builder_temps_alloc_stack(builder);
+
+    const char *enter_fmt = is_async
+        ? "'%.200s' object does not support the asynchronous context manager "
+          "protocol"
+        : "'%.200s' object does not support the context manager protocol";
+    const char *exit_fmt = is_async
+        ? "'%.200s' object does not support the asynchronous context manager "
+          "protocol (missed __aexit__ method)"
+        : "'%.200s' object does not support the context manager protocol "
+          "(missed __exit__ method)";
+    phx_tc_emit(tc, hir_c_create_load_attr_special_reg(
+        enter, manager, enter_id, enter_fmt, &tc->frame));
+    phx_tc_emit(tc, hir_c_create_load_attr_special_reg(
+        exit, manager, exit_id, exit_fmt, &tc->frame));
+    phx_ptr_arr_push(&tc->frame.stack, exit);
+
+    void *enter_result = hir_builder_temps_alloc_stack(builder);
+    /* CallFlags::None = 0. VectorCall(1, enter_result, None) + setFrameState. */
+    void *call = hir_c_create_vectorcall_reg(1, enter_result, 0u);
+    hir_deopt_set_frame_state(call, &tc->frame);
+    hir_c_set_operand(call, 0, enter);
+    phx_tc_emit(tc, call);
+
+    *out_enter_result = enter_result;
+}
+