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
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 (Kind == VK_RISCV_CALL_PLT)
44 OS << "@plt";
45 if (HasVariant)
46 OS << ')';
47 }
48
getPCRelHiFixup(const MCFragment ** DFOut) const49 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
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 .Default(VK_RISCV_Invalid);
124 }
125
getVariantKindName(VariantKind Kind)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
fixELFSymbolsInTLSFixupsImpl(const MCExpr * Expr,MCAssembler & Asm)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
fixELFSymbolsInTLSFixups(MCAssembler & Asm) const190 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
evaluateAsConstant(int64_t & Res) const203 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
evaluateAsInt64(int64_t Value) const223 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