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 assert(Binary < UINT8_MAX && "Multi-byte opcodes not supported yet"); 65 OS << uint8_t(Binary); 66 67 // For br_table instructions, encode the size of the table. In the MCInst, 68 // there's an index operand, one operand for each table entry, and the 69 // default operand. 70 if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 || 71 MI.getOpcode() == WebAssembly::BR_TABLE_I64) 72 encodeULEB128(MI.getNumOperands() - 2, OS); 73 74 const MCInstrDesc &Desc = MCII.get(MI.getOpcode()); 75 for (unsigned i = 0, e = MI.getNumOperands(); i < e; ++i) { 76 const MCOperand &MO = MI.getOperand(i); 77 if (MO.isReg()) { 78 /* nothing to encode */ 79 } else if (MO.isImm()) { 80 if (i < Desc.getNumOperands()) { 81 assert(Desc.TSFlags == 0 && 82 "WebAssembly non-variable_ops don't use TSFlags"); 83 const MCOperandInfo &Info = Desc.OpInfo[i]; 84 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) { 85 encodeSLEB128(int32_t(MO.getImm()), OS); 86 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) { 87 encodeSLEB128(int64_t(MO.getImm()), OS); 88 } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) { 89 llvm_unreachable("wasm globals should only be accessed symbolicly"); 90 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) { 91 encodeSLEB128(int64_t(MO.getImm()), OS); 92 } else { 93 encodeULEB128(uint64_t(MO.getImm()), OS); 94 } 95 } else { 96 assert(Desc.TSFlags == (WebAssemblyII::VariableOpIsImmediate | 97 WebAssemblyII::VariableOpImmediateIsLabel)); 98 encodeULEB128(uint64_t(MO.getImm()), OS); 99 } 100 } else if (MO.isFPImm()) { 101 assert(i < Desc.getNumOperands() && 102 "Unexpected floating-point immediate as a non-fixed operand"); 103 assert(Desc.TSFlags == 0 && 104 "WebAssembly variable_ops floating point ops don't use TSFlags"); 105 const MCOperandInfo &Info = Desc.OpInfo[i]; 106 if (Info.OperandType == WebAssembly::OPERAND_F32IMM) { 107 // TODO: MC converts all floating point immediate operands to double. 108 // This is fine for numeric values, but may cause NaNs to change bits. 109 float f = float(MO.getFPImm()); 110 support::endian::Writer<support::little>(OS).write<float>(f); 111 } else { 112 assert(Info.OperandType == WebAssembly::OPERAND_F64IMM); 113 double d = MO.getFPImm(); 114 support::endian::Writer<support::little>(OS).write<double>(d); 115 } 116 } else if (MO.isExpr()) { 117 const MCOperandInfo &Info = Desc.OpInfo[i]; 118 llvm::MCFixupKind FixupKind; 119 size_t PaddedSize = 5; 120 if (Info.OperandType == WebAssembly::OPERAND_I32IMM) { 121 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i32); 122 } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) { 123 FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i64); 124 PaddedSize = 10; 125 } else if (Info.OperandType == WebAssembly::OPERAND_FUNCTION32 || 126 Info.OperandType == WebAssembly::OPERAND_OFFSET32 || 127 Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) { 128 FixupKind = MCFixupKind(WebAssembly::fixup_code_uleb128_i32); 129 } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) { 130 FixupKind = MCFixupKind(WebAssembly::fixup_code_global_index); 131 } else { 132 llvm_unreachable("unexpected symbolic operand kind"); 133 } 134 Fixups.push_back(MCFixup::create( 135 OS.tell() - Start, MO.getExpr(), 136 FixupKind, MI.getLoc())); 137 ++MCNumFixups; 138 encodeULEB128(0, OS, PaddedSize); 139 } else { 140 llvm_unreachable("unexpected operand kind"); 141 } 142 } 143 144 ++MCNumEmitted; // Keep track of the # of mi's emitted. 145 } 146 147 #include "WebAssemblyGenMCCodeEmitter.inc" 148