[maglev] Convert smi->int32 constant

Bug: v8:7700
Change-Id: I4a772e0b2b821376ba75afd587694e130f059089
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3647831
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80643}

src/maglev/maglev-graph-builder.h

@@ -354,6 +354,8 @@ class MaglevGraphBuilder {
       case ValueRepresentation::kTagged: {
         if (value->Is<CheckedSmiTag>()) {
           return value->input(0).node();
+        } else if (SmiConstant* constant = value->TryCast<SmiConstant>()) {
+          return AddNewNode<Int32Constant>({}, constant->value().value());
         }
         return AddNewConversionNode<CheckedSmiUntag>(reg, value);
       }