[maglev] Unconditionally create LoopPhi for contexts

Contexts are not included into bytecode loop assignment
analysis. We follow TF and create a LoopPhi unconditionally.

Bug: v8:7700
Fixed: chromium:1359662
Change-Id: I1a589a4bae2bbbf14bf637f0c1e0439e66216aae
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3871209
Auto-Submit: Victor Gomes <victorgomes@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82984}

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

@@ -466,7 +466,9 @@ class MergePointInterpreterFrameState {
             entry = state->NewLoopPhi(info.zone(), reg, merge_offset);
           }
         });
-    frame_state.context(info) = nullptr;
+    // TODO(v8:7700): Add contexts into assignment analysis.
+    frame_state.context(info) = state->NewLoopPhi(
+        info.zone(), interpreter::Register::current_context(), merge_offset);
     frame_state.ForEachLocal(
         info, [&](ValueNode*& entry, interpreter::Register reg) {
           entry = nullptr;