1 //=- WebAssemblyMCCodeEmitter.cpp - Convert WebAssembly code to machine code -// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 /// 10 /// \file 11 /// \brief This file implements the WebAssemblyMCCodeEmitter class. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "MCTargetDesc/WebAssemblyFixupKinds.h" 16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 17 #include "llvm/ADT/STLExtras.h" 18 #include "llvm/ADT/Statistic.h" 19 #include "llvm/MC/MCCodeEmitter.h" 20 #include "llvm/MC/MCFixup.h" 21 #include "llvm/MC/MCInst.h" 22 #include "llvm/MC/MCInstrInfo.h" 23 #include "llvm/MC/MCRegisterInfo.h" 24 #include "llvm/MC/MCSubtargetInfo.h" 25 #include "llvm/MC/MCSymbol.h" 26 #include "llvm/Support/Debug.h" 27 #include "llvm/Support/EndianStream.h" 28 #include "llvm/Support/LEB128.h" 29 #include "llvm/Support/raw_ostream.h" 30 31 using namespace llvm; 32 33 #define DEBUG_TYPE "mccodeemitter" 34 35 STATISTIC(MCNumEmitted, "Number of MC instructions emitted."); 36 STATISTIC(MCNumFixups, "Number of MC fixups created."); 37 38 namespace { 39 class WebAssemblyMCCodeEmitter final : public MCCodeEmitter { 40 const MCInstrInfo &MCII; 41 42 // Implementation generated by tablegen. 43 uint64_t getBinaryCodeForInstr(const MCInst &MI, 44 SmallVectorImpl<MCFixup> &Fixups, 45 const MCSubtargetInfo &STI) const; 46 47 void encodeInstruction(const MCInst &MI, raw_ostream &OS, 48 SmallVectorImpl<MCFixup> &Fixups, 49 const MCSubtargetInfo &STI) const override; 50 51 public: 52 WebAssemblyMCCodeEmitter(const MCInstrInfo &mcii) : MCII(mcii) {} 53 }; 54 } // end anonymous namespace 55 56 MCCodeEmitter *llvm::createWebAssemblyMCCodeEmitter(const MCInstrInfo &MCII) { 57 return new WebAssemblyMCCodeEmitter(MCII); 58 } 59 60 void WebAssemblyMCCodeEmitter::encodeInstruction( 61 const MCInst &MI, raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups, 62 const MCSubtargetInfo &STI) const { 63 uint64_t Start = OS.tell(); 64 65 uint64_t Binary = getBinaryCodeForInstr(MI, Fixups, STI); 66 if (Binary <= UINT8_MAX) { 67 OS << uint8_t(Binary); 68 } else { 69 assert(Binary <= UINT16_MAX && "Several-byte opcodes not supported yet"); 70 OS << uint8_t(Binary >> 8) 71 << uint8_t(Binary); 72 } 73 74 // For br_table instructions, encode the size of the table. In the MCInst, 75 // there's an index operand, one operand for each table entry, and the 76 // default operand. 77 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 || 78 MI.getOpcode() == WebAssembly::BR_TABLE_I64) 79 encodeULEB128(MI.getNumOperands() - 2, OS); 80 81 const MCInstrDesc &Desc = MCII.get(MI.getOpcode()); 82 for (unsigned i = 0, e = MI.getNumOperands(); i < e; ++i) { 83 const MCOperand &MO = MI.getOperand(i); 84 if (MO.isReg()) { 85 /* nothing to encode */ 86 } else if (MO.isImm()) { 87 if (i < Desc.getNumOperands()) { 88 assert(Desc.TSFlags == 0 && 89 "WebAssembly non-variable_ops don't use TSFlags"); 90 const MCOperandInfo &Info = Desc.OpInfo[i]; 91 DEBUG(dbgs() << "Encoding immediate: type=" << int(Info.OperandType) << "\n"); 92 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) { 93 encodeSLEB128(int32_t(MO.getImm()), OS); 94 } else if (Info.OperandType == WebAssembly::OPERAND_OFFSET32) { 95 encodeULEB128(uint32_t(MO.getImm()), OS); 96 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) { 97 encodeSLEB128(int64_t(MO.getImm()), OS); 98 } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) { 99 llvm_unreachable("wasm globals should only be accessed symbolicly"); 100 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 101 OS << uint8_t(MO.getImm()); 102 } else { 103 encodeULEB128(uint64_t(MO.getImm()), OS); 104 } 105 } else { 106 assert(Desc.TSFlags == (WebAssemblyII::VariableOpIsImmediate | 107 WebAssemblyII::VariableOpImmediateIsLabel)); 108 encodeULEB128(uint64_t(MO.getImm()), OS); 109 } 110 } else if (MO.isFPImm()) { 111 assert(i < Desc.getNumOperands() && 112 "Unexpected floating-point immediate as a non-fixed operand"); 113 assert(Desc.TSFlags == 0 && 114 "WebAssembly variable_ops floating point ops don't use TSFlags"); 115 const MCOperandInfo &Info = Desc.OpInfo[i]; 116 if (Info.OperandType == WebAssembly::OPERAND_F32IMM) { 117 // TODO: MC converts all floating point immediate operands to double. 118 // This is fine for numeric values, but may cause NaNs to change bits. 119 float f = float(MO.getFPImm()); 120 support::endian::Writer<support::little>(OS).write<float>(f); 121 } else { 122 assert(Info.OperandType == WebAssembly::OPERAND_F64IMM); 123 double d = MO.getFPImm(); 124 support::endian::Writer<support::little>(OS).write<double>(d); 125 } 126 } else if (MO.isExpr()) { 127 const MCOperandInfo &Info = Desc.OpInfo[i]; 128 llvm::MCFixupKind FixupKind; 129 size_t PaddedSize = 5; 130 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) { 131 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i32); 132 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) { 133 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i64); 134 PaddedSize = 10; 135 } else if (Info.OperandType == WebAssembly::OPERAND_FUNCTION32 || 136 Info.OperandType == WebAssembly::OPERAND_OFFSET32 || 137 Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 138 FixupKind = MCFixupKind(WebAssembly::fixup_code_uleb128_i32); 139 } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) { 140 FixupKind = MCFixupKind(WebAssembly::fixup_code_global_index); 141 } else { 142 llvm_unreachable("unexpected symbolic operand kind"); 143 } 144 Fixups.push_back(MCFixup::create( 145 OS.tell() - Start, MO.getExpr(), 146 FixupKind, MI.getLoc())); 147 ++MCNumFixups; 148 encodeULEB128(0, OS, PaddedSize); 149 } else { 150 llvm_unreachable("unexpected operand kind"); 151 } 152 } 153 154 ++MCNumEmitted; // Keep track of the # of mi's emitted. 155 } 156 157 #include "WebAssemblyGenMCCodeEmitter.inc" 158