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
73