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