1 //==- WebAssemblyDisassembler.cpp - Disassembler for WebAssembly -*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// This file is part of the WebAssembly Disassembler.
13 /// It contains code to translate the data produced by the decoder into
16 //===----------------------------------------------------------------------===//
18 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
19 #include "WebAssembly.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
22 #include "llvm/MC/MCFixedLenDisassembler.h"
23 #include "llvm/MC/MCInst.h"
24 #include "llvm/MC/MCInstrInfo.h"
25 #include "llvm/MC/MCSubtargetInfo.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/Support/Endian.h"
28 #include "llvm/Support/LEB128.h"
29 #include "llvm/Support/TargetRegistry.h"
33 #define DEBUG_TYPE "wasm-disassembler"
35 using DecodeStatus = MCDisassembler::DecodeStatus;
37 #include "WebAssemblyGenDisassemblerTables.inc"
40 class WebAssemblyDisassembler final : public MCDisassembler {
41 std::unique_ptr<const MCInstrInfo> MCII;
43 DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
44 ArrayRef<uint8_t> Bytes, uint64_t Address,
46 raw_ostream &CStream) const override;
49 WebAssemblyDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
50 std::unique_ptr<const MCInstrInfo> MCII)
51 : MCDisassembler(STI, Ctx), MCII(std::move(MCII)) {}
53 } // end anonymous namespace
55 static MCDisassembler *createWebAssemblyDisassembler(const Target &T,
56 const MCSubtargetInfo &STI,
58 std::unique_ptr<const MCInstrInfo> MCII(T.createMCInstrInfo());
59 return new WebAssemblyDisassembler(STI, Ctx, std::move(MCII));
62 extern "C" void LLVMInitializeWebAssemblyDisassembler() {
63 // Register the disassembler for each target.
64 TargetRegistry::RegisterMCDisassembler(getTheWebAssemblyTarget32(),
65 createWebAssemblyDisassembler);
66 TargetRegistry::RegisterMCDisassembler(getTheWebAssemblyTarget64(),
67 createWebAssemblyDisassembler);
70 static int nextByte(ArrayRef<uint8_t> Bytes, uint64_t &Size) {
71 if (Size >= Bytes.size())
78 static bool parseLEBImmediate(MCInst &MI, uint64_t &Size,
79 ArrayRef<uint8_t> Bytes, bool Signed) {
81 const char *Error = nullptr;
82 auto Val = Signed ? decodeSLEB128(Bytes.data() + Size, &N,
83 Bytes.data() + Bytes.size(), &Error)
84 : static_cast<int64_t>(
85 decodeULEB128(Bytes.data() + Size, &N,
86 Bytes.data() + Bytes.size(), &Error));
90 MI.addOperand(MCOperand::createImm(Val));
95 bool parseFPImmediate(MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes) {
96 if (Size + sizeof(T) > Bytes.size())
99 memcpy(&Val, Bytes.data() + Size, sizeof(T));
100 support::endian::byte_swap<T, support::endianness::little>(Val);
102 MI.addOperand(MCOperand::createFPImm(static_cast<double>(Val)));
106 MCDisassembler::DecodeStatus WebAssemblyDisassembler::getInstruction(
107 MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes, uint64_t /*Address*/,
108 raw_ostream & /*OS*/, raw_ostream &CS) const {
111 auto Opc = nextByte(Bytes, Size);
113 return MCDisassembler::Fail;
114 const auto *WasmInst = &InstructionTable0[Opc];
115 // If this is a prefix byte, indirect to another table.
116 if (WasmInst->ET == ET_Prefix) {
118 // Linear search, so far only 2 entries.
119 for (auto PT = PrefixTable; PT->Table; PT++) {
120 if (PT->Prefix == Opc) {
121 WasmInst = PT->Table;
126 return MCDisassembler::Fail;
127 Opc = nextByte(Bytes, Size);
129 return MCDisassembler::Fail;
132 if (WasmInst->ET == ET_Unused)
133 return MCDisassembler::Fail;
134 // At this point we must have a valid instruction to decode.
135 assert(WasmInst->ET == ET_Instruction);
136 MI.setOpcode(WasmInst->Opcode);
137 // Parse any operands.
138 for (uint8_t OPI = 0; OPI < WasmInst->NumOperands; OPI++) {
139 switch (WasmInst->Operands[OPI]) {
141 case WebAssembly::OPERAND_BASIC_BLOCK:
142 case WebAssembly::OPERAND_LOCAL:
143 case WebAssembly::OPERAND_GLOBAL:
144 case WebAssembly::OPERAND_FUNCTION32:
145 case WebAssembly::OPERAND_OFFSET32:
146 case WebAssembly::OPERAND_P2ALIGN:
147 case WebAssembly::OPERAND_TYPEINDEX:
148 case MCOI::OPERAND_IMMEDIATE: {
149 if (!parseLEBImmediate(MI, Size, Bytes, false))
150 return MCDisassembler::Fail;
154 case WebAssembly::OPERAND_I32IMM:
155 case WebAssembly::OPERAND_I64IMM:
156 case WebAssembly::OPERAND_SIGNATURE: {
157 if (!parseLEBImmediate(MI, Size, Bytes, true))
158 return MCDisassembler::Fail;
162 case WebAssembly::OPERAND_F32IMM: {
163 if (!parseFPImmediate<float>(MI, Size, Bytes))
164 return MCDisassembler::Fail;
167 case WebAssembly::OPERAND_F64IMM: {
168 if (!parseFPImmediate<double>(MI, Size, Bytes))
169 return MCDisassembler::Fail;
172 case MCOI::OPERAND_REGISTER: {
173 // These are NOT actually in the instruction stream, but MC is going to
174 // expect operands to be present for them!
175 // FIXME: can MC re-generate register assignments or do we have to
176 // do this? Since this function decodes a single instruction, we don't
177 // have the proper context for tracking an operand stack here.
178 MI.addOperand(MCOperand::createReg(0));
182 llvm_unreachable("Unknown operand type in WebAssemblyDisassembler");
185 return MCDisassembler::Success;