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/MCAssembler.h"
19 #include "llvm/MC/MCContext.h"
20 #include "llvm/MC/MCStreamer.h"
21 #include "llvm/MC/MCSymbolELF.h"
22 #include "llvm/MC/MCValue.h"
23 #include "llvm/Support/Casting.h"
24 #include "llvm/Support/ErrorHandling.h"
25
26 using namespace llvm;
27
28 #define DEBUG_TYPE "riscvmcexpr"
29
create(const MCExpr * Expr,VariantKind Kind,MCContext & Ctx)30 const RISCVMCExpr *RISCVMCExpr::create(const MCExpr *Expr, VariantKind Kind,
31 MCContext &Ctx) {
32 return new (Ctx) RISCVMCExpr(Expr, Kind);
33 }
34
printImpl(raw_ostream & OS,const MCAsmInfo * MAI) const35 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 (HasVariant)
44 OS << ')';
45 }
46
getPCRelHiFixup(const MCFragment ** DFOut) const47 const MCFixup *RISCVMCExpr::getPCRelHiFixup(const MCFragment **DFOut) const {
48 MCValue AUIPCLoc;
49 if (!getSubExpr()->evaluateAsRelocatable(AUIPCLoc, nullptr, nullptr))
50 return nullptr;
51
52 const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
53 if (!AUIPCSRE)
54 return nullptr;
55
56 const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
57 const auto *DF = dyn_cast_or_null<MCDataFragment>(AUIPCSymbol->getFragment());
58
59 if (!DF)
60 return nullptr;
61
62 uint64_t Offset = AUIPCSymbol->getOffset();
63 if (DF->getContents().size() == Offset) {
64 DF = dyn_cast_or_null<MCDataFragment>(DF->getNext());
65 if (!DF)
66 return nullptr;
67 Offset = 0;
68 }
69
70 for (const MCFixup &F : DF->getFixups()) {
71 if (F.getOffset() != Offset)
72 continue;
73
74 switch ((unsigned)F.getKind()) {
75 default:
76 continue;
77 case RISCV::fixup_riscv_got_hi20:
78 case RISCV::fixup_riscv_tls_got_hi20:
79 case RISCV::fixup_riscv_tls_gd_hi20:
80 case RISCV::fixup_riscv_pcrel_hi20:
81 case RISCV::fixup_riscv_tlsdesc_hi20:
82 if (DFOut)
83 *DFOut = DF;
84 return &F;
85 }
86 }
87
88 return nullptr;
89 }
90
evaluateAsRelocatableImpl(MCValue & Res,const MCAssembler * Asm,const MCFixup * Fixup) const91 bool RISCVMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
92 const MCAssembler *Asm,
93 const MCFixup *Fixup) const {
94 // Explicitly drop the layout and assembler to prevent any symbolic folding in
95 // the expression handling. This is required to preserve symbolic difference
96 // expressions to emit the paired relocations.
97 if (!getSubExpr()->evaluateAsRelocatable(Res, nullptr, nullptr))
98 return false;
99
100 Res =
101 MCValue::get(Res.getSymA(), Res.getSymB(), Res.getConstant(), getKind());
102 // Custom fixup types are not valid with symbol difference expressions.
103 return Res.getSymB() ? getKind() == VK_RISCV_None : true;
104 }
105
visitUsedExpr(MCStreamer & Streamer) const106 void RISCVMCExpr::visitUsedExpr(MCStreamer &Streamer) const {
107 Streamer.visitUsedExpr(*getSubExpr());
108 }
109
getVariantKindForName(StringRef name)110 RISCVMCExpr::VariantKind RISCVMCExpr::getVariantKindForName(StringRef name) {
111 return StringSwitch<RISCVMCExpr::VariantKind>(name)
112 .Case("lo", VK_RISCV_LO)
113 .Case("hi", VK_RISCV_HI)
114 .Case("pcrel_lo", VK_RISCV_PCREL_LO)
115 .Case("pcrel_hi", VK_RISCV_PCREL_HI)
116 .Case("got_pcrel_hi", VK_RISCV_GOT_HI)
117 .Case("tprel_lo", VK_RISCV_TPREL_LO)
118 .Case("tprel_hi", VK_RISCV_TPREL_HI)
119 .Case("tprel_add", VK_RISCV_TPREL_ADD)
120 .Case("tls_ie_pcrel_hi", VK_RISCV_TLS_GOT_HI)
121 .Case("tls_gd_pcrel_hi", VK_RISCV_TLS_GD_HI)
122 .Case("tlsdesc_hi", VK_RISCV_TLSDESC_HI)
123 .Case("tlsdesc_load_lo", VK_RISCV_TLSDESC_LOAD_LO)
124 .Case("tlsdesc_add_lo", VK_RISCV_TLSDESC_ADD_LO)
125 .Case("tlsdesc_call", VK_RISCV_TLSDESC_CALL)
126 .Default(VK_RISCV_Invalid);
127 }
128
getVariantKindName(VariantKind Kind)129 StringRef RISCVMCExpr::getVariantKindName(VariantKind Kind) {
130 switch (Kind) {
131 case VK_RISCV_Invalid:
132 case VK_RISCV_None:
133 llvm_unreachable("Invalid ELF symbol kind");
134 case VK_RISCV_LO:
135 return "lo";
136 case VK_RISCV_HI:
137 return "hi";
138 case VK_RISCV_PCREL_LO:
139 return "pcrel_lo";
140 case VK_RISCV_PCREL_HI:
141 return "pcrel_hi";
142 case VK_RISCV_GOT_HI:
143 return "got_pcrel_hi";
144 case VK_RISCV_TPREL_LO:
145 return "tprel_lo";
146 case VK_RISCV_TPREL_HI:
147 return "tprel_hi";
148 case VK_RISCV_TPREL_ADD:
149 return "tprel_add";
150 case VK_RISCV_TLS_GOT_HI:
151 return "tls_ie_pcrel_hi";
152 case VK_RISCV_TLSDESC_HI:
153 return "tlsdesc_hi";
154 case VK_RISCV_TLSDESC_LOAD_LO:
155 return "tlsdesc_load_lo";
156 case VK_RISCV_TLSDESC_ADD_LO:
157 return "tlsdesc_add_lo";
158 case VK_RISCV_TLSDESC_CALL:
159 return "tlsdesc_call";
160 case VK_RISCV_TLS_GD_HI:
161 return "tls_gd_pcrel_hi";
162 case VK_RISCV_CALL:
163 return "call";
164 case VK_RISCV_CALL_PLT:
165 return "call_plt";
166 case VK_RISCV_32_PCREL:
167 return "32_pcrel";
168 }
169 llvm_unreachable("Invalid ELF symbol kind");
170 }
171
fixELFSymbolsInTLSFixupsImpl(const MCExpr * Expr,MCAssembler & Asm)172 static void fixELFSymbolsInTLSFixupsImpl(const MCExpr *Expr, MCAssembler &Asm) {
173 switch (Expr->getKind()) {
174 case MCExpr::Target:
175 llvm_unreachable("Can't handle nested target expression");
176 break;
177 case MCExpr::Constant:
178 break;
179
180 case MCExpr::Binary: {
181 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Expr);
182 fixELFSymbolsInTLSFixupsImpl(BE->getLHS(), Asm);
183 fixELFSymbolsInTLSFixupsImpl(BE->getRHS(), Asm);
184 break;
185 }
186
187 case MCExpr::SymbolRef: {
188 // We're known to be under a TLS fixup, so any symbol should be
189 // modified. There should be only one.
190 const MCSymbolRefExpr &SymRef = *cast<MCSymbolRefExpr>(Expr);
191 cast<MCSymbolELF>(SymRef.getSymbol()).setType(ELF::STT_TLS);
192 break;
193 }
194
195 case MCExpr::Unary:
196 fixELFSymbolsInTLSFixupsImpl(cast<MCUnaryExpr>(Expr)->getSubExpr(), Asm);
197 break;
198 }
199 }
200
fixELFSymbolsInTLSFixups(MCAssembler & Asm) const201 void RISCVMCExpr::fixELFSymbolsInTLSFixups(MCAssembler &Asm) const {
202 switch (getKind()) {
203 default:
204 return;
205 case VK_RISCV_TPREL_HI:
206 case VK_RISCV_TLS_GOT_HI:
207 case VK_RISCV_TLS_GD_HI:
208 case VK_RISCV_TLSDESC_HI:
209 break;
210 }
211
212 fixELFSymbolsInTLSFixupsImpl(getSubExpr(), Asm);
213 }
214
evaluateAsConstant(int64_t & Res) const215 bool RISCVMCExpr::evaluateAsConstant(int64_t &Res) const {
216 MCValue Value;
217
218 if (Kind == VK_RISCV_PCREL_HI || Kind == VK_RISCV_PCREL_LO ||
219 Kind == VK_RISCV_GOT_HI || Kind == VK_RISCV_TPREL_HI ||
220 Kind == VK_RISCV_TPREL_LO || Kind == VK_RISCV_TPREL_ADD ||
221 Kind == VK_RISCV_TLS_GOT_HI || Kind == VK_RISCV_TLS_GD_HI ||
222 Kind == VK_RISCV_TLSDESC_HI || Kind == VK_RISCV_TLSDESC_LOAD_LO ||
223 Kind == VK_RISCV_TLSDESC_ADD_LO || Kind == VK_RISCV_TLSDESC_CALL ||
224 Kind == VK_RISCV_CALL || Kind == VK_RISCV_CALL_PLT)
225 return false;
226
227 if (!getSubExpr()->evaluateAsRelocatable(Value, nullptr, nullptr))
228 return false;
229
230 if (!Value.isAbsolute())
231 return false;
232
233 Res = evaluateAsInt64(Value.getConstant());
234 return true;
235 }
236
evaluateAsInt64(int64_t Value) const237 int64_t RISCVMCExpr::evaluateAsInt64(int64_t Value) const {
238 switch (Kind) {
239 default:
240 llvm_unreachable("Invalid kind");
241 case VK_RISCV_LO:
242 return SignExtend64<12>(Value);
243 case VK_RISCV_HI:
244 // Add 1 if bit 11 is 1, to compensate for low 12 bits being negative.
245 return ((Value + 0x800) >> 12) & 0xfffff;
246 }
247 }
248