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