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  1. //===--------------------- CodeEmitter.h ------------------------*- C++ -*-===//
  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. /// \file
  9. ///
  10. /// A utility class used to compute instruction encodings. It buffers encodings
  11. /// for later usage. It exposes a simple API to compute and get the encodings as
  12. /// StringRef.
  13. //
  14. //===----------------------------------------------------------------------===//
  15.  
  16. #ifndef LLVM_MCA_CODEEMITTER_H
  17. #define LLVM_MCA_CODEEMITTER_H
  18.  
  19. #include "llvm/ADT/ArrayRef.h"
  20. #include "llvm/ADT/SmallString.h"
  21. #include "llvm/ADT/StringRef.h"
  22. #include "llvm/MC/MCAsmBackend.h"
  23. #include "llvm/MC/MCCodeEmitter.h"
  24. #include "llvm/MC/MCInst.h"
  25. #include "llvm/MC/MCSubtargetInfo.h"
  26. #include "llvm/Support/raw_ostream.h"
  27.  
  28. namespace llvm {
  29. namespace mca {
  30.  
  31. /// A utility class used to compute instruction encodings for a code region.
  32. ///
  33. /// It provides a simple API to compute and return instruction encodings as
  34. /// strings. Encodings are cached internally for later usage.
  35. class CodeEmitter {
  36.   const MCSubtargetInfo &STI;
  37.   const MCAsmBackend &MAB;
  38.   const MCCodeEmitter &MCE;
  39.  
  40.   SmallString<256> Code;
  41.   raw_svector_ostream VecOS;
  42.   ArrayRef<MCInst> Sequence;
  43.  
  44.   // An EncodingInfo pair stores <base, length> information.  Base (i.e. first)
  45.   // is an index to the `Code`. Length (i.e. second) is the encoding size.
  46.   using EncodingInfo = std::pair<unsigned, unsigned>;
  47.  
  48.   // A cache of encodings.
  49.   SmallVector<EncodingInfo, 16> Encodings;
  50.  
  51.   EncodingInfo getOrCreateEncodingInfo(unsigned MCID);
  52.  
  53. public:
  54.   CodeEmitter(const MCSubtargetInfo &ST, const MCAsmBackend &AB,
  55.               const MCCodeEmitter &CE, ArrayRef<MCInst> S)
  56.       : STI(ST), MAB(AB), MCE(CE), VecOS(Code), Sequence(S),
  57.         Encodings(S.size()) {}
  58.  
  59.   StringRef getEncoding(unsigned MCID) {
  60.     EncodingInfo EI = getOrCreateEncodingInfo(MCID);
  61.     return StringRef(&Code[EI.first], EI.second);
  62.   }
  63. };
  64.  
  65. } // namespace mca
  66. } // namespace llvm
  67.  
  68. #endif // LLVM_MCA_CODEEMITTER_H
  69.