CodeEmitter.h revision 360784 
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
32namespace llvm {
33namespace 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.
39class 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
57public:
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