[maglev] Drop non-empty block DCHECK

It might be wrong for bytecode blocks that only juggle registers.

Bug: v8:7700
Change-Id: Idf495112d278e1899a1bbd1f92128fcc2edf6074
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3579103
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79875}

src/maglev/maglev-graph-builder.h

@@ -100,7 +100,9 @@ class MaglevGraphBuilder {
     int offset = iterator_.current_offset();
     if (V8_UNLIKELY(merge_states_[offset] != nullptr)) {
       if (current_block_ != nullptr) {
-        DCHECK(!current_block_->nodes().is_empty());
+        // TODO(leszeks): Re-evaluate this DCHECK, we might hit it if the only
+        // bytecodes in this basic block were only register juggling.
+        // DCHECK(!current_block_->nodes().is_empty());
         FinishBlock<Jump>(offset, {}, &jump_targets_[offset]);
 
         merge_states_[offset]->Merge(*compilation_unit_,