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/Compiler.h"
27
28namespace llvm {
29namespace 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.
35class CodeEmitter {
36 const MCSubtargetInfo &STI;
37 const MCAsmBackend &MAB;
38 const MCCodeEmitter &MCE;
39
40 SmallString<256> Code;
41 ArrayRef<MCInst> Sequence;
42
43 // An EncodingInfo pair stores <base, length> information. Base (i.e. first)
44 // is an index to the `Code`. Length (i.e. second) is the encoding size.
45 using EncodingInfo = std::pair<unsigned, unsigned>;
46
47 // A cache of encodings.
48 SmallVector<EncodingInfo, 16> Encodings;
49
50 LLVM_ABI EncodingInfo getOrCreateEncodingInfo(unsigned MCID);
51
52public:
53 CodeEmitter(const MCSubtargetInfo &ST, const MCAsmBackend &AB,
54 const MCCodeEmitter &CE, ArrayRef<MCInst> S)
55 : STI(ST), MAB(AB), MCE(CE), Sequence(S), Encodings(S.size()) {}
56
57 StringRef getEncoding(unsigned MCID) {
58 EncodingInfo EI = getOrCreateEncodingInfo(MCID);
59 return StringRef(&Code[EI.first], EI.second);
60 }
61};
62
63} // namespace mca
64} // namespace llvm
65
66#endif // LLVM_MCA_CODEEMITTER_H
67