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
create(const MCExpr * Expr,VariantKind Kind,MCContext & Ctx)31 const RISCVMCExpr *RISCVMCExpr::create(const MCExpr *Expr, VariantKind Kind,
32 MCContext &Ctx) {
33 return new (Ctx) RISCVMCExpr(Expr, Kind);
34 }
35
printImpl(raw_ostream & OS,const MCAsmInfo * MAI) const36 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 (HasVariant)
45 OS << ')';
46 }
47
getPCRelHiFixup(const MCFragment ** DFOut) const48 const MCFixup *RISCVMCExpr::getPCRelHiFixup(const MCFragment **DFOut) const {
49 MCValue AUIPCLoc;
50 if (!getSubExpr()->evaluateAsRelocatable(AUIPCLoc, nullptr, nullptr))
51 return nullptr;
52
53 const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
54 if (!AUIPCSRE)
55 return nullptr;
56
57 const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
58 const auto *DF = dyn_cast_or_null<MCDataFragment>(AUIPCSymbol->getFragment());
59
60 if (!DF)
61 return nullptr;
62
63 uint64_t Offset = AUIPCSymbol->getOffset();
64 if (DF->getContents().size() == Offset) {
65 DF = dyn_cast_or_null<MCDataFragment>(DF->getNextNode());
66 if (!DF)
67 return nullptr;
68 Offset = 0;
69 }
70
71 for (const MCFixup &F : DF->getFixups()) {
72 if (F.getOffset() != Offset)
73 continue;
74
75 switch ((unsigned)F.getKind()) {
76 default:
77 continue;
78 case RISCV::fixup_riscv_got_hi20:
79 case RISCV::fixup_riscv_tls_got_hi20:
80 case RISCV::fixup_riscv_tls_gd_hi20:
81 case RISCV::fixup_riscv_pcrel_hi20:
82 case RISCV::fixup_riscv_tlsdesc_hi20:
83 if (DFOut)
84 *DFOut = DF;
85 return &F;
86 }
87 }
88
89 return nullptr;
90 }
91
evaluateAsRelocatableImpl(MCValue & Res,const MCAsmLayout * Layout,const MCFixup * Fixup) const92 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
visitUsedExpr(MCStreamer & Streamer) const107 void RISCVMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
108 Streamer.visitUsedExpr(*getSubExpr());
109 }
110
getVariantKindForName(StringRef name)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 .Case("tlsdesc_hi", VK_RISCV_TLSDESC_HI)
124 .Case("tlsdesc_load_lo", VK_RISCV_TLSDESC_LOAD_LO)
125 .Case("tlsdesc_add_lo", VK_RISCV_TLSDESC_ADD_LO)
126 .Case("tlsdesc_call", VK_RISCV_TLSDESC_CALL)
127 .Default(VK_RISCV_Invalid);
128 }
129
getVariantKindName(VariantKind Kind)130 StringRef RISCVMCExpr::getVariantKindName(VariantKind Kind) {
131 switch (Kind) {
132 case VK_RISCV_Invalid:
133 case VK_RISCV_None:
134 llvm_unreachable("Invalid ELF symbol kind");
135 case VK_RISCV_LO:
136 return "lo";
137 case VK_RISCV_HI:
138 return "hi";
139 case VK_RISCV_PCREL_LO:
140 return "pcrel_lo";
141 case VK_RISCV_PCREL_HI:
142 return "pcrel_hi";
143 case VK_RISCV_GOT_HI:
144 return "got_pcrel_hi";
145 case VK_RISCV_TPREL_LO:
146 return "tprel_lo";
147 case VK_RISCV_TPREL_HI:
148 return "tprel_hi";
149 case VK_RISCV_TPREL_ADD:
150 return "tprel_add";
151 case VK_RISCV_TLS_GOT_HI:
152 return "tls_ie_pcrel_hi";
153 case VK_RISCV_TLSDESC_HI:
154 return "tlsdesc_hi";
155 case VK_RISCV_TLSDESC_LOAD_LO:
156 return "tlsdesc_load_lo";
157 case VK_RISCV_TLSDESC_ADD_LO:
158 return "tlsdesc_add_lo";
159 case VK_RISCV_TLSDESC_CALL:
160 return "tlsdesc_call";
161 case VK_RISCV_TLS_GD_HI:
162 return "tls_gd_pcrel_hi";
163 case VK_RISCV_CALL:
164 return "call";
165 case VK_RISCV_CALL_PLT:
166 return "call_plt";
167 case VK_RISCV_32_PCREL:
168 return "32_pcrel";
169 }
170 llvm_unreachable("Invalid ELF symbol kind");
171 }
172
fixELFSymbolsInTLSFixupsImpl(const MCExpr * Expr,MCAssembler & Asm)173 static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
174 switch (Expr->getKind()) {
175 case MCExpr::Target:
176 llvm_unreachable("Can't handle nested target expression");
177 break;
178 case MCExpr::Constant:
179 break;
180
181 case MCExpr::Binary: {
182 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr);
183 fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm);
184 fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm);
185 break;
186 }
187
188 case MCExpr::SymbolRef: {
189 // We're known to be under a TLS fixup, so any symbol should be
190 // modified. There should be only one.
191 const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr);
192 cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS);
193 break;
194 }
195
196 case MCExpr::Unary:
197 fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm);
198 break;
199 }
200 }
201
fixELFSymbolsInTLSFixups(MCAssembler & Asm) const202 void RISCVMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
203 switch (getKind()) {
204 default:
205 return;
206 case VK_RISCV_TPREL_HI:
207 case VK_RISCV_TLS_GOT_HI:
208 case VK_RISCV_TLS_GD_HI:
209 case VK_RISCV_TLSDESC_HI:
210 break;
211 }
212
213 fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm);
214 }
215
evaluateAsConstant(int64_t & Res) const216 bool RISCVMCExpr::evaluateAsConstant(int64_t &Res) const {
217 MCValue Value;
218
219 if (Kind == VK_RISCV_PCREL_HI || Kind == VK_RISCV_PCREL_LO ||
220 Kind == VK_RISCV_GOT_HI || Kind == VK_RISCV_TPREL_HI ||
221 Kind == VK_RISCV_TPREL_LO || Kind == VK_RISCV_TPREL_ADD ||
222 Kind == VK_RISCV_TLS_GOT_HI || Kind == VK_RISCV_TLS_GD_HI ||
223 Kind == VK_RISCV_TLSDESC_HI || Kind == VK_RISCV_TLSDESC_LOAD_LO ||
224 Kind == VK_RISCV_TLSDESC_ADD_LO || Kind == VK_RISCV_TLSDESC_CALL ||
225 Kind == VK_RISCV_CALL || Kind == VK_RISCV_CALL_PLT)
226 return false;
227
228 if (!getSubExpr()->evaluateAsRelocatable(Value, nullptr, nullptr))
229 return false;
230
231 if (!Value.isAbsolute())
232 return false;
233
234 Res = evaluateAsInt64(Value.getConstant());
235 return true;
236 }
237
evaluateAsInt64(int64_t Value) const238 int64_t RISCVMCExpr::evaluateAsInt64(int64_t Value) const {
239 switch (Kind) {
240 default:
241 llvm_unreachable("Invalid kind");
242 case VK_RISCV_LO:
243 return SignExtend64<12>(Value);
244 case VK_RISCV_HI:
245 // Add 1 if bit 11 is 1, to compensate for low 12 bits being negative.
246 return ((Value + 0x800) >> 12) & 0xfffff;
247 }
248 }
249