1 //===-- RISCVMCExpr.cpp - RISC-V specific MC expression classes -----------===// 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 // This file contains the implementation of the assembly expression modifiers 10 // accepted by the RISC-V architecture (e.g. ":lo12:", ":gottprel_g1:", ...). 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "RISCVMCExpr.h" 15 #include "MCTargetDesc/RISCVAsmBackend.h" 16 #include "RISCVFixupKinds.h" 17 #include "llvm/BinaryFormat/ELF.h" 18 #include "llvm/MC/MCAsmLayout.h" 19 #include "llvm/MC/MCAssembler.h" 20 #include "llvm/MC/MCContext.h" 21 #include "llvm/MC/MCStreamer.h" 22 #include "llvm/MC/MCSymbolELF.h" 23 #include "llvm/MC/MCValue.h" 24 #include "llvm/Support/Casting.h" 25 #include "llvm/Support/ErrorHandling.h" 26 27 using namespace llvm; 28 29 #define DEBUG_TYPE "riscvmcexpr" 30 31 const RISCVMCExpr *RISCVMCExpr::create(const MCExpr *Expr, VariantKind Kind, 32 MCContext &Ctx) { 33 return new (Ctx) RISCVMCExpr(Expr, Kind); 34 } 35 36 void RISCVMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const { 37 VariantKind Kind = getKind(); 38 bool HasVariant = ((Kind != VK_RISCV_None) && (Kind != VK_RISCV_CALL) && 39 (Kind != VK_RISCV_CALL_PLT)); 40 41 if (HasVariant) 42 OS << '%' << getVariantKindName(getKind()) << '('; 43 Expr->print(OS, MAI); 44 if (Kind == VK_RISCV_CALL_PLT) 45 OS << "@plt"; 46 if (HasVariant) 47 OS << ')'; 48 } 49 50 const MCFixup *RISCVMCExpr::getPCRelHiFixup(const MCFragment **DFOut) const { 51 MCValue AUIPCLoc; 52 if (!getSubExpr()->evaluateAsRelocatable(AUIPCLoc, nullptr, nullptr)) 53 return nullptr; 54 55 const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA(); 56 if (!AUIPCSRE) 57 return nullptr; 58 59 const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol(); 60 const auto *DF = dyn_cast_or_null<MCDataFragment>(AUIPCSymbol->getFragment()); 61 62 if (!DF) 63 return nullptr; 64 65 uint64_t Offset = AUIPCSymbol->getOffset(); 66 if (DF->getContents().size() == Offset) { 67 DF = dyn_cast_or_null<MCDataFragment>(DF->getNextNode()); 68 if (!DF) 69 return nullptr; 70 Offset = 0; 71 } 72 73 for (const MCFixup &F : DF->getFixups()) { 74 if (F.getOffset() != Offset) 75 continue; 76 77 switch ((unsigned)F.getKind()) { 78 default: 79 continue; 80 case RISCV::fixup_riscv_got_hi20: 81 case RISCV::fixup_riscv_tls_got_hi20: 82 case RISCV::fixup_riscv_tls_gd_hi20: 83 case RISCV::fixup_riscv_pcrel_hi20: 84 if (DFOut) 85 *DFOut = DF; 86 return &F; 87 } 88 } 89 90 return nullptr; 91 } 92 93 bool RISCVMCExpr::evaluateAsRelocatableImpl(MCValue &Res, 94 const MCAsmLayout *Layout, 95 const MCFixup *Fixup) const { 96 // Explicitly drop the layout and assembler to prevent any symbolic folding in 97 // the expression handling. This is required to preserve symbolic difference 98 // expressions to emit the paired relocations. 99 if (!getSubExpr()->evaluateAsRelocatable(Res, nullptr, nullptr)) 100 return false; 101 102 Res = 103 MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(), getKind()); 104 // Custom fixup types are not valid with symbol difference expressions. 105 return Res.getSymB() ? getKind() == VK_RISCV_None : true; 106 } 107 108 void RISCVMCExpr::visitUsedExpr(MCStreamer &Streamer) const { 109 Streamer.visitUsedExpr(*getSubExpr()); 110 } 111 112 RISCVMCExpr::VariantKind RISCVMCExpr::getVariantKindForName(StringRef name) { 113 return StringSwitch<RISCVMCExpr::VariantKind>(name) 114 .Case("lo", VK_RISCV_LO) 115 .Case("hi", VK_RISCV_HI) 116 .Case("pcrel_lo", VK_RISCV_PCREL_LO) 117 .Case("pcrel_hi", VK_RISCV_PCREL_HI) 118 .Case("got_pcrel_hi", VK_RISCV_GOT_HI) 119 .Case("tprel_lo", VK_RISCV_TPREL_LO) 120 .Case("tprel_hi", VK_RISCV_TPREL_HI) 121 .Case("tprel_add", VK_RISCV_TPREL_ADD) 122 .Case("tls_ie_pcrel_hi", VK_RISCV_TLS_GOT_HI) 123 .Case("tls_gd_pcrel_hi", VK_RISCV_TLS_GD_HI) 124 .Default(VK_RISCV_Invalid); 125 } 126 127 StringRef RISCVMCExpr::getVariantKindName(VariantKind Kind) { 128 switch (Kind) { 129 case VK_RISCV_Invalid: 130 case VK_RISCV_None: 131 llvm_unreachable("Invalid ELF symbol kind"); 132 case VK_RISCV_LO: 133 return "lo"; 134 case VK_RISCV_HI: 135 return "hi"; 136 case VK_RISCV_PCREL_LO: 137 return "pcrel_lo"; 138 case VK_RISCV_PCREL_HI: 139 return "pcrel_hi"; 140 case VK_RISCV_GOT_HI: 141 return "got_pcrel_hi"; 142 case VK_RISCV_TPREL_LO: 143 return "tprel_lo"; 144 case VK_RISCV_TPREL_HI: 145 return "tprel_hi"; 146 case VK_RISCV_TPREL_ADD: 147 return "tprel_add"; 148 case VK_RISCV_TLS_GOT_HI: 149 return "tls_ie_pcrel_hi"; 150 case VK_RISCV_TLS_GD_HI: 151 return "tls_gd_pcrel_hi"; 152 case VK_RISCV_CALL: 153 return "call"; 154 case VK_RISCV_CALL_PLT: 155 return "call_plt"; 156 case VK_RISCV_32_PCREL: 157 return "32_pcrel"; 158 } 159 llvm_unreachable("Invalid ELF symbol kind"); 160 } 161 162 static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) { 163 switch (Expr->getKind()) { 164 case MCExpr::Target: 165 llvm_unreachable("Can't handle nested target expression"); 166 break; 167 case MCExpr::Constant: 168 break; 169 170 case MCExpr::Binary: { 171 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr); 172 fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm); 173 fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm); 174 break; 175 } 176 177 case MCExpr::SymbolRef: { 178 // We're known to be under a TLS fixup, so any symbol should be 179 // modified. There should be only one. 180 const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr); 181 cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS); 182 break; 183 } 184 185 case MCExpr::Unary: 186 fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm); 187 break; 188 } 189 } 190 191 void RISCVMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const { 192 switch (getKind()) { 193 default: 194 return; 195 case VK_RISCV_TPREL_HI: 196 case VK_RISCV_TLS_GOT_HI: 197 case VK_RISCV_TLS_GD_HI: 198 break; 199 } 200 201 fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm); 202 } 203 204 bool RISCVMCExpr::evaluateAsConstant(int64_t &Res) const { 205 MCValue Value; 206 207 if (Kind == VK_RISCV_PCREL_HI || Kind == VK_RISCV_PCREL_LO || 208 Kind == VK_RISCV_GOT_HI || Kind == VK_RISCV_TPREL_HI || 209 Kind == VK_RISCV_TPREL_LO || Kind == VK_RISCV_TPREL_ADD || 210 Kind == VK_RISCV_TLS_GOT_HI || Kind == VK_RISCV_TLS_GD_HI || 211 Kind == VK_RISCV_CALL || Kind == VK_RISCV_CALL_PLT) 212 return false; 213 214 if (!getSubExpr()->evaluateAsRelocatable(Value, nullptr, nullptr)) 215 return false; 216 217 if (!Value.isAbsolute()) 218 return false; 219 220 Res = evaluateAsInt64(Value.getConstant()); 221 return true; 222 } 223 224 int64_t RISCVMCExpr::evaluateAsInt64(int64_t Value) const { 225 switch (Kind) { 226 default: 227 llvm_unreachable("Invalid kind"); 228 case VK_RISCV_LO: 229 return SignExtend64<12>(Value); 230 case VK_RISCV_HI: 231 // Add 1 if bit 11 is 1, to compensate for low 12 bits being negative. 232 return ((Value + 0x800) >> 12) & 0xfffff; 233 } 234 } 235