[maglev] Allow closure register access

Allow bytecodes processed by maglev to access the on-stack closure
register.

Bug: v8:7700
Change-Id: I757d0c1734ef478e5b9671ed87a4691101b4e29d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3506444
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79383}

src/maglev/maglev-graph-builder.h

@@ -63,19 +63,14 @@ class MaglevGraphBuilder {
       current_interpreter_frame_.set(reg, AddNewNode<InitialValue>({}, reg));
     }
 
-    // interpreter::Register regs[] = {interpreter::Register::current_context(),
-    //                                 interpreter::Register::function_closure(),
-    //                                 interpreter::Register::bytecode_array(),
-    //                                 interpreter::Register::bytecode_offset()};
-    // for (interpreter::Register& reg : regs) {
-    //   current_interpreter_frame_.set(reg, AddNewNode<InitialValue>({}, reg));
-    // }
-
-    // TODO(leszeks): Extract out a separate "incoming context" node to be able
-    // to read in the context arg but also use the frame-spilled context var.
-    current_interpreter_frame_.set(
-        interpreter::Register::current_context(),
-        AddNewNode<InitialValue>({}, interpreter::Register::current_context()));
+    // TODO(leszeks): Extract out a separate "incoming context/closure" nodes,
+    // to be able to read in the machine register but also use the frame-spilled
+    // slot.
+    interpreter::Register regs[] = {interpreter::Register::current_context(),
+                                    interpreter::Register::function_closure()};
+    for (interpreter::Register& reg : regs) {
+      current_interpreter_frame_.set(reg, AddNewNode<InitialValue>({}, reg));
+    }
 
     interpreter::Register new_target_or_generator_register =
         bytecode().incoming_new_target_or_generator_register();

src/maglev/maglev-interpreter-frame-state.h

@@ -48,6 +48,7 @@ class InterpreterFrameState {
   void set(interpreter::Register reg, ValueNode* value) {
     DCHECK_IMPLIES(reg.is_parameter(),
                    reg == interpreter::Register::current_context() ||
+                       reg == interpreter::Register::function_closure() ||
                        reg.ToParameterIndex() >= 0);
     frame_[reg] = value;
   }