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