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  1. //===-- UnreachableBlockElim.h - Remove unreachable blocks for codegen --===//
  2. //
  3. // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  4. // See https://llvm.org/LICENSE.txt for license information.
  5. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  6. //
  7. //===----------------------------------------------------------------------===//
  8. //
  9. // This pass is an extremely simple version of the SimplifyCFG pass.  Its sole
  10. // job is to delete LLVM basic blocks that are not reachable from the entry
  11. // node.  To do this, it performs a simple depth first traversal of the CFG,
  12. // then deletes any unvisited nodes.
  13. //
  14. // Note that this pass is really a hack.  In particular, the instruction
  15. // selectors for various targets should just not generate code for unreachable
  16. // blocks.  Until LLVM has a more systematic way of defining instruction
  17. // selectors, however, we cannot really expect them to handle additional
  18. // complexity.
  19. //
  20. //===----------------------------------------------------------------------===//
  21.  
  22. #ifndef LLVM_CODEGEN_UNREACHABLEBLOCKELIM_H
  23. #define LLVM_CODEGEN_UNREACHABLEBLOCKELIM_H
  24.  
  25. #include "llvm/IR/PassManager.h"
  26.  
  27. namespace llvm {
  28.  
  29. class UnreachableBlockElimPass
  30.     : public PassInfoMixin<UnreachableBlockElimPass> {
  31. public:
  32.   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
  33. };
  34. } // end namespace llvm
  35.  
  36. #endif // LLVM_CODEGEN_UNREACHABLEBLOCKELIM_H
  37.