[maglev] Show root constant name in BranchIf

Bug: v8:7700
Change-Id: I83ba4baff9b014a6f0bc6b91bb1ad3f66622e2ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3878168
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83015}

src/maglev/maglev-ir.cc

@@ -3585,6 +3585,10 @@ void BranchIfRootConstant::GenerateCode(MaglevCodeGenState* code_gen_state,
   __ CompareRoot(ToRegister(condition_input()), root_index());
   Branch(code_gen_state, equal, if_true(), if_false(), state.next_block());
 }
+void BranchIfRootConstant::PrintParams(
+    std::ostream& os, MaglevGraphLabeller* graph_labeller) const {
+  os << "(" << RootsTable::name(root_index_) << ")";
+}
 
 void BranchIfUndefinedOrNull::AllocateVreg(
     MaglevVregAllocationState* vreg_state) {

src/maglev/maglev-ir.h

@@ -3928,7 +3928,7 @@ class BranchIfRootConstant
 
   void AllocateVreg(MaglevVregAllocationState*);
   void GenerateCode(MaglevCodeGenState*, const ProcessingState&);
-  void PrintParams(std::ostream&, MaglevGraphLabeller*) const {}
+  void PrintParams(std::ostream&, MaglevGraphLabeller*) const;
 
  private:
   RootIndex root_index_;