1 //=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -// 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 /// 9 /// \file 10 /// This file implements the WebAssemblyMCCodeEmitter class. 11 /// 12 //===----------------------------------------------------------------------===// 13 14 #include "MCTargetDesc/WebAssemblyFixupKinds.h" 15 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/Statistic.h" 18 #include "llvm/MC/MCCodeEmitter.h" 19 #include "llvm/MC/MCFixup.h" 20 #include "llvm/MC/MCInst.h" 21 #include "llvm/MC/MCInstrInfo.h" 22 #include "llvm/MC/MCRegisterInfo.h" 23 #include "llvm/MC/MCSubtargetInfo.h" 24 #include "llvm/MC/MCSymbol.h" 25 #include "llvm/Support/Debug.h" 26 #include "llvm/Support/EndianStream.h" 27 #include "llvm/Support/LEB128.h" 28 #include "llvm/Support/raw_ostream.h" 29 30 using namespace llvm; 31 32 #define DEBUG_TYPE "mccodeemitter" 33 34 STATISTIC(MCNumEmitted, "Number of MC instructions emitted."); 35 STATISTIC(MCNumFixups, "Number of MC fixups created."); 36 37 namespace { 38 class WebAssemblyMCCodeEmitter final : public MCCodeEmitter { 39 const MCInstrInfo &MCII; 40 41 // Implementation generated by tablegen. 42 uint64_t getBinaryCodeForInstr(const MCInst &MI, 43 SmallVectorImpl<MCFixup> &Fixups, 44 const MCSubtargetInfo &STI) const; 45 46 void encodeInstruction(const MCInst &MI, raw_ostream &OS, 47 SmallVectorImpl<MCFixup> &Fixups, 48 const MCSubtargetInfo &STI) const override; 49 50 public: 51 WebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) : MCII(MCII) {} 52 }; 53 } // end anonymous namespace 54 55 MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) { 56 return new WebAssemblyMCCodeEmitter(MCII); 57 } 58 59 void WebAssemblyMCCodeEmitter::encodeInstruction( 60 const MCInst &MI, raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups, 61 const MCSubtargetInfo &STI) const { 62 uint64_t Start = OS.tell(); 63 64 uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI); 65 if (Binary <= UINT8_MAX) { 66 OS << uint8_t(Binary); 67 } else { 68 assert(Binary <= UINT16_MAX && "Several-byte opcodes not supported yet"); 69 OS << uint8_t(Binary >> 8); 70 encodeULEB128(uint8_t(Binary), OS); 71 } 72 73 // For br_table instructions, encode the size of the table. In the MCInst, 74 // there's an index operand (if not a stack instruction), one operand for 75 // each table entry, and the default operand. 76 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32_S || 77 MI.getOpcode() == WebAssembly::BR_TABLE_I64_S) 78 encodeULEB128(MI.getNumOperands() - 1, OS); 79 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 || 80 MI.getOpcode() == WebAssembly::BR_TABLE_I64) 81 encodeULEB128(MI.getNumOperands() - 2, OS); 82 83 const MCInstrDesc &Desc = MCII.get(MI.getOpcode()); 84 for (unsigned I = 0, E = MI.getNumOperands(); I < E; ++I) { 85 const MCOperand &MO = MI.getOperand(I); 86 if (MO.isReg()) { 87 /* nothing to encode */ 88 89 } else if (MO.isImm()) { 90 if (I < Desc.getNumOperands()) { 91 const MCOperandInfo &Info = Desc.OpInfo[I]; 92 LLVM_DEBUG(dbgs() << "Encoding immediate: type=" 93 << int(Info.OperandType) << "\n"); 94 switch (Info.OperandType) { 95 case WebAssembly::OPERAND_I32IMM: 96 encodeSLEB128(int32_t(MO.getImm()), OS); 97 break; 98 case WebAssembly::OPERAND_OFFSET32: 99 encodeULEB128(uint32_t(MO.getImm()), OS); 100 break; 101 case WebAssembly::OPERAND_I64IMM: 102 encodeSLEB128(int64_t(MO.getImm()), OS); 103 break; 104 case WebAssembly::OPERAND_SIGNATURE: 105 OS << uint8_t(MO.getImm()); 106 break; 107 case WebAssembly::OPERAND_VEC_I8IMM: 108 support::endian::write<uint8_t>(OS, MO.getImm(), support::little); 109 break; 110 case WebAssembly::OPERAND_VEC_I16IMM: 111 support::endian::write<uint16_t>(OS, MO.getImm(), support::little); 112 break; 113 case WebAssembly::OPERAND_VEC_I32IMM: 114 support::endian::write<uint32_t>(OS, MO.getImm(), support::little); 115 break; 116 case WebAssembly::OPERAND_VEC_I64IMM: 117 support::endian::write<uint64_t>(OS, MO.getImm(), support::little); 118 break; 119 case WebAssembly::OPERAND_GLOBAL: 120 llvm_unreachable("wasm globals should only be accessed symbolicly"); 121 default: 122 encodeULEB128(uint64_t(MO.getImm()), OS); 123 } 124 } else { 125 encodeULEB128(uint64_t(MO.getImm()), OS); 126 } 127 128 } else if (MO.isFPImm()) { 129 const MCOperandInfo &Info = Desc.OpInfo[I]; 130 if (Info.OperandType == WebAssembly::OPERAND_F32IMM) { 131 // TODO: MC converts all floating point immediate operands to double. 132 // This is fine for numeric values, but may cause NaNs to change bits. 133 auto F = float(MO.getFPImm()); 134 support::endian::write<float>(OS, F, support::little); 135 } else { 136 assert(Info.OperandType == WebAssembly::OPERAND_F64IMM); 137 double D = MO.getFPImm(); 138 support::endian::write<double>(OS, D, support::little); 139 } 140 141 } else if (MO.isExpr()) { 142 const MCOperandInfo &Info = Desc.OpInfo[I]; 143 llvm::MCFixupKind FixupKind; 144 size_t PaddedSize = 5; 145 switch (Info.OperandType) { 146 case WebAssembly::OPERAND_I32IMM: 147 FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i32); 148 break; 149 case WebAssembly::OPERAND_I64IMM: 150 FixupKind = MCFixupKind(WebAssembly::fixup_sleb128_i64); 151 PaddedSize = 10; 152 break; 153 case WebAssembly::OPERAND_FUNCTION32: 154 case WebAssembly::OPERAND_OFFSET32: 155 case WebAssembly::OPERAND_SIGNATURE: 156 case WebAssembly::OPERAND_TYPEINDEX: 157 case WebAssembly::OPERAND_GLOBAL: 158 case WebAssembly::OPERAND_EVENT: 159 FixupKind = MCFixupKind(WebAssembly::fixup_uleb128_i32); 160 break; 161 default: 162 llvm_unreachable("unexpected symbolic operand kind"); 163 } 164 Fixups.push_back(MCFixup::create(OS.tell() - Start, MO.getExpr(), 165 FixupKind, MI.getLoc())); 166 ++MCNumFixups; 167 encodeULEB128(0, OS, PaddedSize); 168 } else { 169 llvm_unreachable("unexpected operand kind"); 170 } 171 } 172 173 ++MCNumEmitted; // Keep track of the # of mi's emitted. 174 } 175 176 #include "WebAssemblyGenMCCodeEmitter.inc" 177