include/llvm/MCA/CodeEmitter.h

   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/StringRef.h"
  21 #include "llvm/MC/MCAsmBackend.h"
  22 #include "llvm/MC/MCCodeEmitter.h"
  23 #include "llvm/MC/MCFixup.h"
  24 #include "llvm/MC/MCInst.h"
  25 #include "llvm/MC/MCSubtargetInfo.h"
  26 #include "llvm/MCA/Instruction.h"
  27 #include "llvm/MCA/Support.h"
  28 #include "llvm/Support/raw_ostream.h"
  29
  30 #include <string>
  31
  32 namespace llvm {
  33 namespace mca {
  34
  35 /// A utility class used to compute instruction encodings for a code region.
  36 ///
  37 /// It provides a simple API to compute and return instruction encodings as
  38 /// strings. Encodings are cached internally for later usage.
  39 class CodeEmitter {
  40   const MCSubtargetInfo &STI;
  41   const MCAsmBackend &MAB;
  42   const MCCodeEmitter &MCE;
  43
  44   SmallString<256> Code;
  45   raw_svector_ostream VecOS;
  46   ArrayRef<MCInst> Sequence;
  47
  48   // An EncodingInfo pair stores <base, length> information.  Base (i.e. first)
  49   // is an index to the `Code`. Length (i.e. second) is the encoding size.
  50   using EncodingInfo = std::pair<unsigned, unsigned>;
  51
  52   // A cache of encodings.
  53   SmallVector<EncodingInfo, 16> Encodings;
  54
  55   EncodingInfo getOrCreateEncodingInfo(unsigned MCID);
  56
  57 public:
  58   CodeEmitter(const MCSubtargetInfo &ST, const MCAsmBackend &AB,
  59               const MCCodeEmitter &CE, ArrayRef<MCInst> S)
  60       : STI(ST), MAB(AB), MCE(CE), VecOS(Code), Sequence(S),
  61         Encodings(S.size()) {}
  62
  63   StringRef getEncoding(unsigned MCID) {
  64     EncodingInfo EI = getOrCreateEncodingInfo(MCID);
  65     return StringRef(&Code[EI.first], EI.second);
  66   }
  67 };
  68
  69 } // namespace mca
  70 } // namespace llvm
  71
  72 #endif // LLVM_MCA_CODEEMITTER_H