1//===-- ARMUnwindOpAsm.cpp - ARM Unwind Opcodes Assembler -------*- C++ -*-===// 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// This file implements the unwind opcode assmebler for ARM exception handling 11// table. 12// 13//===----------------------------------------------------------------------===// 14 15#include "ARMUnwindOpAsm.h" 16#include "llvm/Support/ARMEHABI.h" 17#include "llvm/Support/ErrorHandling.h" 18#include "llvm/Support/LEB128.h" 19 20using namespace llvm; 21 22namespace { 23 /// UnwindOpcodeStreamer - The simple wrapper over SmallVector to emit bytes 24 /// with MSB to LSB per uint32_t ordering. For example, the first byte will 25 /// be placed in Vec[3], and the following bytes will be placed in 2, 1, 0, 26 /// 7, 6, 5, 4, 11, 10, 9, 8, and so on. 27 class UnwindOpcodeStreamer { 28 private: 29 SmallVectorImpl<uint8_t> &Vec; 30 size_t Pos; 31 32 public: 33 UnwindOpcodeStreamer(SmallVectorImpl<uint8_t> &V) : Vec(V), Pos(3) { 34 } 35 36 /// Emit the byte in MSB to LSB per uint32_t order. 37 inline void EmitByte(uint8_t elem) { 38 Vec[Pos] = elem; 39 Pos = (((Pos ^ 0x3u) + 1) ^ 0x3u); 40 } 41 42 /// Emit the size prefix. 43 inline void EmitSize(size_t Size) { 44 size_t SizeInWords = (Size + 3) / 4; 45 assert(SizeInWords <= 0x100u && 46 "Only 256 additional words are allowed for unwind opcodes"); 47 EmitByte(static_cast<uint8_t>(SizeInWords - 1)); 48 } 49 50 /// Emit the personality index prefix. 51 inline void EmitPersonalityIndex(unsigned PI) { 52 assert(PI < ARM::EHABI::NUM_PERSONALITY_INDEX && 53 "Invalid personality prefix"); 54 EmitByte(ARM::EHABI::EHT_COMPACT | PI); 55 } 56 57 /// Fill the rest of bytes with FINISH opcode. 58 inline void FillFinishOpcode() { 59 while (Pos < Vec.size()) 60 EmitByte(ARM::EHABI::UNWIND_OPCODE_FINISH); 61 } 62 }; 63} 64 65void UnwindOpcodeAssembler::EmitRegSave(uint32_t RegSave) { 66 if (RegSave == 0u) 67 return; 68 69 // One byte opcode to save register r14 and r11-r4 70 if (RegSave & (1u << 4)) { 71 // The one byte opcode will always save r4, thus we can't use the one byte 72 // opcode when r4 is not in .save directive. 73 74 // Compute the consecutive registers from r4 to r11. 75 uint32_t Range = 0; 76 uint32_t Mask = (1u << 4); 77 for (uint32_t Bit = (1u << 5); Bit < (1u << 12); Bit <<= 1) { 78 if ((RegSave & Bit) == 0u) 79 break; 80 ++Range; 81 Mask |= Bit; 82 } 83 84 // Emit this opcode when the mask covers every registers. 85 uint32_t UnmaskedReg = RegSave & 0xfff0u & (~Mask); 86 if (UnmaskedReg == 0u) { 87 // Pop r[4 : (4 + n)] 88 EmitInt8(ARM::EHABI::UNWIND_OPCODE_POP_REG_RANGE_R4 | Range); 89 RegSave &= 0x000fu; 90 } else if (UnmaskedReg == (1u << 14)) { 91 // Pop r[14] + r[4 : (4 + n)] 92 EmitInt8(ARM::EHABI::UNWIND_OPCODE_POP_REG_RANGE_R4_R14 | Range); 93 RegSave &= 0x000fu; 94 } 95 } 96 97 // Two bytes opcode to save register r15-r4 98 if ((RegSave & 0xfff0u) != 0) 99 EmitInt16(ARM::EHABI::UNWIND_OPCODE_POP_REG_MASK_R4 | (RegSave >> 4)); 100 101 // Opcode to save register r3-r0 102 if ((RegSave & 0x000fu) != 0) 103 EmitInt16(ARM::EHABI::UNWIND_OPCODE_POP_REG_MASK | (RegSave & 0x000fu)); 104} 105 106/// Emit unwind opcodes for .vsave directives 107void UnwindOpcodeAssembler::EmitVFPRegSave(uint32_t VFPRegSave) { 108 size_t i = 32; 109 110 while (i > 16) { 111 uint32_t Bit = 1u << (i - 1); 112 if ((VFPRegSave & Bit) == 0u) { 113 --i; 114 continue; 115 } 116 117 uint32_t Range = 0; 118 119 --i; 120 Bit >>= 1; 121 122 while (i > 16 && (VFPRegSave & Bit)) { 123 --i; 124 ++Range; 125 Bit >>= 1; 126 } 127 128 EmitInt16(ARM::EHABI::UNWIND_OPCODE_POP_VFP_REG_RANGE_FSTMFDD_D16 | 129 ((i - 16) << 4) | Range); 130 } 131 132 while (i > 0) { 133 uint32_t Bit = 1u << (i - 1); 134 if ((VFPRegSave & Bit) == 0u) { 135 --i; 136 continue; 137 } 138 139 uint32_t Range = 0; 140 141 --i; 142 Bit >>= 1; 143 144 while (i > 0 && (VFPRegSave & Bit)) { 145 --i; 146 ++Range; 147 Bit >>= 1; 148 } 149 150 EmitInt16(ARM::EHABI::UNWIND_OPCODE_POP_VFP_REG_RANGE_FSTMFDD | (i << 4) | 151 Range); 152 } 153} 154 155/// Emit unwind opcodes to copy address from source register to $sp. 156void UnwindOpcodeAssembler::EmitSetSP(uint16_t Reg) { 157 EmitInt8(ARM::EHABI::UNWIND_OPCODE_SET_VSP | Reg); 158} 159 160/// Emit unwind opcodes to add $sp with an offset. 161void UnwindOpcodeAssembler::EmitSPOffset(int64_t Offset) { 162 if (Offset > 0x200) { 163 uint8_t Buff[16]; 164 Buff[0] = ARM::EHABI::UNWIND_OPCODE_INC_VSP_ULEB128; 165 size_t ULEBSize = encodeULEB128((Offset - 0x204) >> 2, Buff + 1); 166 EmitBytes(Buff, ULEBSize + 1); 167 } else if (Offset > 0) { 168 if (Offset > 0x100) { 169 EmitInt8(ARM::EHABI::UNWIND_OPCODE_INC_VSP | 0x3fu); 170 Offset -= 0x100; 171 } 172 EmitInt8(ARM::EHABI::UNWIND_OPCODE_INC_VSP | 173 static_cast<uint8_t>((Offset - 4) >> 2)); 174 } else if (Offset < 0) { 175 while (Offset < -0x100) { 176 EmitInt8(ARM::EHABI::UNWIND_OPCODE_DEC_VSP | 0x3fu); 177 Offset += 0x100; 178 } 179 EmitInt8(ARM::EHABI::UNWIND_OPCODE_DEC_VSP | 180 static_cast<uint8_t>(((-Offset) - 4) >> 2)); 181 } 182} 183 184void UnwindOpcodeAssembler::Finalize(unsigned &PersonalityIndex, 185 SmallVectorImpl<uint8_t> &Result) { 186 187 UnwindOpcodeStreamer OpStreamer(Result); 188 189 if (HasPersonality) { 190 // User-specifed personality routine: [ SIZE , OP1 , OP2 , ... ] 191 PersonalityIndex = ARM::EHABI::NUM_PERSONALITY_INDEX; 192 size_t TotalSize = Ops.size() + 1; 193 size_t RoundUpSize = (TotalSize + 3) / 4 * 4; 194 Result.resize(RoundUpSize); 195 OpStreamer.EmitSize(RoundUpSize); 196 } else { 197 // If no personalityindex is specified, select ane 198 if (PersonalityIndex == ARM::EHABI::NUM_PERSONALITY_INDEX) 199 PersonalityIndex = (Ops.size() <= 3) ? ARM::EHABI::AEABI_UNWIND_CPP_PR0 200 : ARM::EHABI::AEABI_UNWIND_CPP_PR1; 201 if (PersonalityIndex == ARM::EHABI::AEABI_UNWIND_CPP_PR0) { 202 // __aeabi_unwind_cpp_pr0: [ 0x80 , OP1 , OP2 , OP3 ] 203 assert(Ops.size() <= 3 && "too many opcodes for __aeabi_unwind_cpp_pr0"); 204 Result.resize(4); 205 OpStreamer.EmitPersonalityIndex(PersonalityIndex); 206 } else { 207 // __aeabi_unwind_cpp_pr{1,2}: [ {0x81,0x82} , SIZE , OP1 , OP2 , ... ] 208 size_t TotalSize = Ops.size() + 2; 209 size_t RoundUpSize = (TotalSize + 3) / 4 * 4; 210 Result.resize(RoundUpSize); 211 OpStreamer.EmitPersonalityIndex(PersonalityIndex); 212 OpStreamer.EmitSize(RoundUpSize); 213 } 214 } 215 216 // Copy the unwind opcodes 217 for (size_t i = OpBegins.size() - 1; i > 0; --i) 218 for (size_t j = OpBegins[i - 1], end = OpBegins[i]; j < end; ++j) 219 OpStreamer.EmitByte(Ops[j]); 220 221 // Emit the padding finish opcodes if the size is not multiple of 4. 222 OpStreamer.FillFinishOpcode(); 223 224 // Reset the assembler state 225 Reset(); 226} 227