message: On accept scalar broadcasting for the new grid size.
diff: @@ -2405,7 +2405,14 @@ Status IrEmitterUnnested::EmitTargetElementLoop(
  bool few_waves = false;
  auto is_good_for_few_waves = [](const HloInstruction* instr) {
  - return instr->opcode() != HloOpcode::kReduceWindow;
  + if (instr->opcode() == HloOpcode::kReduceWindow) {
  + return false;
  + } else if (instr->opcode() == HloOpcode::kBroadcast &&
  + !instr->dimensions().empty()) {
  + // We need to make the codegen broadcast aware before enabling.
  + return false;
  + }
  + return true;
  };
  if (hlo.opcode() == HloOpcode::kFusion) {
  few_waves = absl::c_all_of(
  