1 //===-- PPCAsmBackend.cpp - PPC Assembler Backend -------------------------===//
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 #include "MCTargetDesc/PPCFixupKinds.h"
10 #include "MCTargetDesc/PPCMCTargetDesc.h"
11 #include "llvm/BinaryFormat/ELF.h"
12 #include "llvm/BinaryFormat/MachO.h"
13 #include "llvm/MC/MCAsmBackend.h"
14 #include "llvm/MC/MCAssembler.h"
15 #include "llvm/MC/MCELFObjectWriter.h"
16 #include "llvm/MC/MCFixupKindInfo.h"
17 #include "llvm/MC/MCMachObjectWriter.h"
18 #include "llvm/MC/MCObjectWriter.h"
19 #include "llvm/MC/MCSectionMachO.h"
20 #include "llvm/MC/MCSubtargetInfo.h"
21 #include "llvm/MC/MCSymbolELF.h"
22 #include "llvm/MC/MCSymbolXCOFF.h"
23 #include "llvm/MC/MCValue.h"
24 #include "llvm/MC/TargetRegistry.h"
25 #include "llvm/Support/ErrorHandling.h"
26 using namespace llvm;
27
adjustFixupValue(unsigned Kind,uint64_t Value)28 static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
29 switch (Kind) {
30 default:
31 llvm_unreachable("Unknown fixup kind!");
32 case FK_Data_1:
33 case FK_Data_2:
34 case FK_Data_4:
35 case FK_Data_8:
36 case PPC::fixup_ppc_nofixup:
37 return Value;
38 case PPC::fixup_ppc_brcond14:
39 case PPC::fixup_ppc_brcond14abs:
40 return Value & 0xfffc;
41 case PPC::fixup_ppc_br24:
42 case PPC::fixup_ppc_br24abs:
43 case PPC::fixup_ppc_br24_notoc:
44 return Value & 0x3fffffc;
45 case PPC::fixup_ppc_half16:
46 return Value & 0xffff;
47 case PPC::fixup_ppc_half16ds:
48 case PPC::fixup_ppc_half16dq:
49 return Value & 0xfffc;
50 case PPC::fixup_ppc_pcrel34:
51 case PPC::fixup_ppc_imm34:
52 return Value & 0x3ffffffff;
53 }
54 }
55
getFixupKindNumBytes(unsigned Kind)56 static unsigned getFixupKindNumBytes(unsigned Kind) {
57 switch (Kind) {
58 default:
59 llvm_unreachable("Unknown fixup kind!");
60 case FK_Data_1:
61 return 1;
62 case FK_Data_2:
63 case PPC::fixup_ppc_half16:
64 case PPC::fixup_ppc_half16ds:
65 case PPC::fixup_ppc_half16dq:
66 return 2;
67 case FK_Data_4:
68 case PPC::fixup_ppc_brcond14:
69 case PPC::fixup_ppc_brcond14abs:
70 case PPC::fixup_ppc_br24:
71 case PPC::fixup_ppc_br24abs:
72 case PPC::fixup_ppc_br24_notoc:
73 return 4;
74 case PPC::fixup_ppc_pcrel34:
75 case PPC::fixup_ppc_imm34:
76 case FK_Data_8:
77 return 8;
78 case PPC::fixup_ppc_nofixup:
79 return 0;
80 }
81 }
82
83 namespace {
84
85 class PPCAsmBackend : public MCAsmBackend {
86 protected:
87 Triple TT;
88 public:
PPCAsmBackend(const Target & T,const Triple & TT)89 PPCAsmBackend(const Target &T, const Triple &TT)
90 : MCAsmBackend(TT.isLittleEndian() ? llvm::endianness::little
91 : llvm::endianness::big),
92 TT(TT) {}
93
getNumFixupKinds() const94 unsigned getNumFixupKinds() const override {
95 return PPC::NumTargetFixupKinds;
96 }
97
getFixupKindInfo(MCFixupKind Kind) const98 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
99 const static MCFixupKindInfo InfosBE[PPC::NumTargetFixupKinds] = {
100 // name offset bits flags
101 { "fixup_ppc_br24", 6, 24, MCFixupKindInfo::FKF_IsPCRel },
102 { "fixup_ppc_br24_notoc", 6, 24, MCFixupKindInfo::FKF_IsPCRel },
103 { "fixup_ppc_brcond14", 16, 14, MCFixupKindInfo::FKF_IsPCRel },
104 { "fixup_ppc_br24abs", 6, 24, 0 },
105 { "fixup_ppc_brcond14abs", 16, 14, 0 },
106 { "fixup_ppc_half16", 0, 16, 0 },
107 { "fixup_ppc_half16ds", 0, 14, 0 },
108 { "fixup_ppc_pcrel34", 0, 34, MCFixupKindInfo::FKF_IsPCRel },
109 { "fixup_ppc_imm34", 0, 34, 0 },
110 { "fixup_ppc_nofixup", 0, 0, 0 }
111 };
112 const static MCFixupKindInfo InfosLE[PPC::NumTargetFixupKinds] = {
113 // name offset bits flags
114 { "fixup_ppc_br24", 2, 24, MCFixupKindInfo::FKF_IsPCRel },
115 { "fixup_ppc_br24_notoc", 2, 24, MCFixupKindInfo::FKF_IsPCRel },
116 { "fixup_ppc_brcond14", 2, 14, MCFixupKindInfo::FKF_IsPCRel },
117 { "fixup_ppc_br24abs", 2, 24, 0 },
118 { "fixup_ppc_brcond14abs", 2, 14, 0 },
119 { "fixup_ppc_half16", 0, 16, 0 },
120 { "fixup_ppc_half16ds", 2, 14, 0 },
121 { "fixup_ppc_pcrel34", 0, 34, MCFixupKindInfo::FKF_IsPCRel },
122 { "fixup_ppc_imm34", 0, 34, 0 },
123 { "fixup_ppc_nofixup", 0, 0, 0 }
124 };
125
126 // Fixup kinds from .reloc directive are like R_PPC_NONE/R_PPC64_NONE. They
127 // do not require any extra processing.
128 if (Kind >= FirstLiteralRelocationKind)
129 return MCAsmBackend::getFixupKindInfo(FK_NONE);
130
131 if (Kind < FirstTargetFixupKind)
132 return MCAsmBackend::getFixupKindInfo(Kind);
133
134 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
135 "Invalid kind!");
136 return (Endian == llvm::endianness::little
137 ? InfosLE
138 : InfosBE)[Kind - FirstTargetFixupKind];
139 }
140
applyFixup(const MCAssembler & Asm,const MCFixup & Fixup,const MCValue & Target,MutableArrayRef<char> Data,uint64_t Value,bool IsResolved,const MCSubtargetInfo * STI) const141 void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
142 const MCValue &Target, MutableArrayRef<char> Data,
143 uint64_t Value, bool IsResolved,
144 const MCSubtargetInfo *STI) const override {
145 MCFixupKind Kind = Fixup.getKind();
146 if (Kind >= FirstLiteralRelocationKind)
147 return;
148 Value = adjustFixupValue(Kind, Value);
149 if (!Value) return; // Doesn't change encoding.
150
151 unsigned Offset = Fixup.getOffset();
152 unsigned NumBytes = getFixupKindNumBytes(Kind);
153
154 // For each byte of the fragment that the fixup touches, mask in the bits
155 // from the fixup value. The Value has been "split up" into the appropriate
156 // bitfields above.
157 for (unsigned i = 0; i != NumBytes; ++i) {
158 unsigned Idx =
159 Endian == llvm::endianness::little ? i : (NumBytes - 1 - i);
160 Data[Offset + i] |= uint8_t((Value >> (Idx * 8)) & 0xff);
161 }
162 }
163
shouldForceRelocation(const MCAssembler & Asm,const MCFixup & Fixup,const MCValue & Target,const MCSubtargetInfo * STI)164 bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
165 const MCValue &Target,
166 const MCSubtargetInfo *STI) override {
167 MCFixupKind Kind = Fixup.getKind();
168 switch ((unsigned)Kind) {
169 default:
170 return Kind >= FirstLiteralRelocationKind;
171 case PPC::fixup_ppc_br24:
172 case PPC::fixup_ppc_br24abs:
173 case PPC::fixup_ppc_br24_notoc:
174 // If the target symbol has a local entry point we must not attempt
175 // to resolve the fixup directly. Emit a relocation and leave
176 // resolution of the final target address to the linker.
177 if (const MCSymbolRefExpr *A = Target.getSymA()) {
178 if (const auto *S = dyn_cast<MCSymbolELF>(&A->getSymbol())) {
179 // The "other" values are stored in the last 6 bits of the second
180 // byte. The traditional defines for STO values assume the full byte
181 // and thus the shift to pack it.
182 unsigned Other = S->getOther() << 2;
183 if ((Other & ELF::STO_PPC64_LOCAL_MASK) != 0)
184 return true;
185 } else if (const auto *S = dyn_cast<MCSymbolXCOFF>(&A->getSymbol())) {
186 return !Target.isAbsolute() && S->isExternal() &&
187 S->getStorageClass() == XCOFF::C_WEAKEXT;
188 }
189 }
190 return false;
191 }
192 }
193
fixupNeedsRelaxation(const MCFixup & Fixup,uint64_t Value,const MCRelaxableFragment * DF,const MCAsmLayout & Layout) const194 bool fixupNeedsRelaxation(const MCFixup &Fixup,
195 uint64_t Value,
196 const MCRelaxableFragment *DF,
197 const MCAsmLayout &Layout) const override {
198 // FIXME.
199 llvm_unreachable("relaxInstruction() unimplemented");
200 }
201
relaxInstruction(MCInst & Inst,const MCSubtargetInfo & STI) const202 void relaxInstruction(MCInst &Inst,
203 const MCSubtargetInfo &STI) const override {
204 // FIXME.
205 llvm_unreachable("relaxInstruction() unimplemented");
206 }
207
writeNopData(raw_ostream & OS,uint64_t Count,const MCSubtargetInfo * STI) const208 bool writeNopData(raw_ostream &OS, uint64_t Count,
209 const MCSubtargetInfo *STI) const override {
210 uint64_t NumNops = Count / 4;
211 for (uint64_t i = 0; i != NumNops; ++i)
212 support::endian::write<uint32_t>(OS, 0x60000000, Endian);
213
214 OS.write_zeros(Count % 4);
215
216 return true;
217 }
218 };
219 } // end anonymous namespace
220
221
222 // FIXME: This should be in a separate file.
223 namespace {
224
225 class ELFPPCAsmBackend : public PPCAsmBackend {
226 public:
ELFPPCAsmBackend(const Target & T,const Triple & TT)227 ELFPPCAsmBackend(const Target &T, const Triple &TT) : PPCAsmBackend(T, TT) {}
228
229 std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const230 createObjectTargetWriter() const override {
231 uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS());
232 bool Is64 = TT.isPPC64();
233 return createPPCELFObjectWriter(Is64, OSABI);
234 }
235
236 std::optional<MCFixupKind> getFixupKind(StringRef Name) const override;
237 };
238
239 class XCOFFPPCAsmBackend : public PPCAsmBackend {
240 public:
XCOFFPPCAsmBackend(const Target & T,const Triple & TT)241 XCOFFPPCAsmBackend(const Target &T, const Triple &TT)
242 : PPCAsmBackend(T, TT) {}
243
244 std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const245 createObjectTargetWriter() const override {
246 return createPPCXCOFFObjectWriter(TT.isArch64Bit());
247 }
248
249 std::optional<MCFixupKind> getFixupKind(StringRef Name) const override;
250 };
251
252 } // end anonymous namespace
253
254 std::optional<MCFixupKind>
getFixupKind(StringRef Name) const255 ELFPPCAsmBackend::getFixupKind(StringRef Name) const {
256 if (TT.isOSBinFormatELF()) {
257 unsigned Type;
258 if (TT.isPPC64()) {
259 Type = llvm::StringSwitch<unsigned>(Name)
260 #define ELF_RELOC(X, Y) .Case(#X, Y)
261 #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def"
262 #undef ELF_RELOC
263 .Case("BFD_RELOC_NONE", ELF::R_PPC64_NONE)
264 .Case("BFD_RELOC_16", ELF::R_PPC64_ADDR16)
265 .Case("BFD_RELOC_32", ELF::R_PPC64_ADDR32)
266 .Case("BFD_RELOC_64", ELF::R_PPC64_ADDR64)
267 .Default(-1u);
268 } else {
269 Type = llvm::StringSwitch<unsigned>(Name)
270 #define ELF_RELOC(X, Y) .Case(#X, Y)
271 #include "llvm/BinaryFormat/ELFRelocs/PowerPC.def"
272 #undef ELF_RELOC
273 .Case("BFD_RELOC_NONE", ELF::R_PPC_NONE)
274 .Case("BFD_RELOC_16", ELF::R_PPC_ADDR16)
275 .Case("BFD_RELOC_32", ELF::R_PPC_ADDR32)
276 .Default(-1u);
277 }
278 if (Type != -1u)
279 return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
280 }
281 return std::nullopt;
282 }
283
284 std::optional<MCFixupKind>
getFixupKind(StringRef Name) const285 XCOFFPPCAsmBackend::getFixupKind(StringRef Name) const {
286 return StringSwitch<std::optional<MCFixupKind>>(Name)
287 .Case("R_REF", (MCFixupKind)PPC::fixup_ppc_nofixup)
288 .Default(std::nullopt);
289 }
290
createPPCAsmBackend(const Target & T,const MCSubtargetInfo & STI,const MCRegisterInfo & MRI,const MCTargetOptions & Options)291 MCAsmBackend *llvm::createPPCAsmBackend(const Target &T,
292 const MCSubtargetInfo &STI,
293 const MCRegisterInfo &MRI,
294 const MCTargetOptions &Options) {
295 const Triple &TT = STI.getTargetTriple();
296 if (TT.isOSBinFormatXCOFF())
297 return new XCOFFPPCAsmBackend(T, TT);
298
299 return new ELFPPCAsmBackend(T, TT);
300 }
301