[maglev] CheckMaps: Deopt if the object is a Smi

Bug: v8:7700
Change-Id: Ib5b6b570829cfb7de9c61115b45bb37437c70dde
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3702804
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81159}

src/maglev/maglev-ir.cc

@@ -622,6 +622,10 @@ void CheckMaps::AllocateVreg(MaglevVregAllocationState* vreg_state,
 void CheckMaps::GenerateCode(MaglevCodeGenState* code_gen_state,
                              const ProcessingState& state) {
   Register object = ToRegister(actual_map_input());
+
+  Condition is_smi = __ CheckSmi(object);
+  EmitEagerDeoptIf(is_smi, code_gen_state, this);
+
   RegList temps = temporaries();
   Register map_tmp = temps.PopFirst();