text: // Copyright 2020 The XLS Authors
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  #ifndef XLS_PASSES_TABLE_SWITCH_PASS_H_
  #define XLS_PASSES_TABLE_SWITCH_PASS_H_
  
  #include "absl/status/statusor.h"
  #include "xls/passes/passes.h"
  
  namespace xls {
  
  // TableSwitchPass converts chains of Select nodes into ArrayIndex ops.
  // These chains have the form:
  // sel.(N)(eq.X, literal.A, literal.B)
  // sel.(N+1)(eq.Y, sel.(N), literal.C)
  // sel.(N+2)(eq.Z, sel.(N+1), literal.D)
  // And so on. In these chains, eq.X, eq.Y, and eq.Z must all be comparisons of
  // the same value against different literals.
  //
  // Current limitations:
  //  - Either the start or end index in the chain must be 0.
  //  - The increment between indices must be positive or negative 1.
  //  - There can be no "gaps" between indices.
  //  - The Select ops have to be binary (i.e., selecting between only two cases).
  class TableSwitchPass : public FunctionBasePass {
   public:
    TableSwitchPass()
        : FunctionBasePass("table_switch", "Table switch conversion") {}
  
   protected:
    absl::StatusOr<bool> RunOnFunctionBaseInternal(
        FunctionBase* f, const PassOptions& options,
        PassResults* results) const override;
  };
  
  }  // namespace xls
  
  #endif  // XLS_PASSES_TABLE_SWITCH_PASS_H_
  