1 //===-- AArch64AsmBackend.cpp - AArch64 Assembler Backend -----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "AArch64.h"
11 #include "AArch64RegisterInfo.h"
12 #include "MCTargetDesc/AArch64FixupKinds.h"
13 #include "llvm/ADT/Triple.h"
14 #include "llvm/MC/MCAsmBackend.h"
15 #include "llvm/MC/MCDirectives.h"
16 #include "llvm/MC/MCELFObjectWriter.h"
17 #include "llvm/MC/MCFixupKindInfo.h"
18 #include "llvm/MC/MCObjectWriter.h"
19 #include "llvm/MC/MCSectionELF.h"
20 #include "llvm/MC/MCSectionMachO.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/MachO.h"
23 using namespace llvm;
24
25 namespace {
26
27 class AArch64AsmBackend : public MCAsmBackend {
28 static const unsigned PCRelFlagVal =
29 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits | MCFixupKindInfo::FKF_IsPCRel;
30
31 public:
AArch64AsmBackend(const Target & T)32 AArch64AsmBackend(const Target &T) : MCAsmBackend() {}
33
getNumFixupKinds() const34 unsigned getNumFixupKinds() const override {
35 return AArch64::NumTargetFixupKinds;
36 }
37
getFixupKindInfo(MCFixupKind Kind) const38 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
39 const static MCFixupKindInfo Infos[AArch64::NumTargetFixupKinds] = {
40 // This table *must* be in the order that the fixup_* kinds are defined in
41 // AArch64FixupKinds.h.
42 //
43 // Name Offset (bits) Size (bits) Flags
44 { "fixup_aarch64_pcrel_adr_imm21", 0, 32, PCRelFlagVal },
45 { "fixup_aarch64_pcrel_adrp_imm21", 0, 32, PCRelFlagVal },
46 { "fixup_aarch64_add_imm12", 10, 12, 0 },
47 { "fixup_aarch64_ldst_imm12_scale1", 10, 12, 0 },
48 { "fixup_aarch64_ldst_imm12_scale2", 10, 12, 0 },
49 { "fixup_aarch64_ldst_imm12_scale4", 10, 12, 0 },
50 { "fixup_aarch64_ldst_imm12_scale8", 10, 12, 0 },
51 { "fixup_aarch64_ldst_imm12_scale16", 10, 12, 0 },
52 { "fixup_aarch64_ldr_pcrel_imm19", 5, 19, PCRelFlagVal },
53 { "fixup_aarch64_movw", 5, 16, 0 },
54 { "fixup_aarch64_pcrel_branch14", 5, 14, PCRelFlagVal },
55 { "fixup_aarch64_pcrel_branch19", 5, 19, PCRelFlagVal },
56 { "fixup_aarch64_pcrel_branch26", 0, 26, PCRelFlagVal },
57 { "fixup_aarch64_pcrel_call26", 0, 26, PCRelFlagVal },
58 { "fixup_aarch64_tlsdesc_call", 0, 0, 0 }
59 };
60
61 if (Kind < FirstTargetFixupKind)
62 return MCAsmBackend::getFixupKindInfo(Kind);
63
64 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
65 "Invalid kind!");
66 return Infos[Kind - FirstTargetFixupKind];
67 }
68
69 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
70 uint64_t Value, bool IsPCRel) const override;
71
72 bool mayNeedRelaxation(const MCInst &Inst) const override;
73 bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
74 const MCRelaxableFragment *DF,
75 const MCAsmLayout &Layout) const override;
76 void relaxInstruction(const MCInst &Inst, MCInst &Res) const override;
77 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
78
HandleAssemblerFlag(MCAssemblerFlag Flag)79 void HandleAssemblerFlag(MCAssemblerFlag Flag) {}
80
getPointerSize() const81 unsigned getPointerSize() const { return 8; }
82 };
83
84 } // end anonymous namespace
85
86 /// \brief The number of bytes the fixup may change.
getFixupKindNumBytes(unsigned Kind)87 static unsigned getFixupKindNumBytes(unsigned Kind) {
88 switch (Kind) {
89 default:
90 llvm_unreachable("Unknown fixup kind!");
91
92 case AArch64::fixup_aarch64_tlsdesc_call:
93 return 0;
94
95 case FK_Data_1:
96 return 1;
97
98 case FK_Data_2:
99 case AArch64::fixup_aarch64_movw:
100 return 2;
101
102 case AArch64::fixup_aarch64_pcrel_branch14:
103 case AArch64::fixup_aarch64_add_imm12:
104 case AArch64::fixup_aarch64_ldst_imm12_scale1:
105 case AArch64::fixup_aarch64_ldst_imm12_scale2:
106 case AArch64::fixup_aarch64_ldst_imm12_scale4:
107 case AArch64::fixup_aarch64_ldst_imm12_scale8:
108 case AArch64::fixup_aarch64_ldst_imm12_scale16:
109 case AArch64::fixup_aarch64_ldr_pcrel_imm19:
110 case AArch64::fixup_aarch64_pcrel_branch19:
111 return 3;
112
113 case AArch64::fixup_aarch64_pcrel_adr_imm21:
114 case AArch64::fixup_aarch64_pcrel_adrp_imm21:
115 case AArch64::fixup_aarch64_pcrel_branch26:
116 case AArch64::fixup_aarch64_pcrel_call26:
117 case FK_Data_4:
118 return 4;
119
120 case FK_Data_8:
121 return 8;
122 }
123 }
124
AdrImmBits(unsigned Value)125 static unsigned AdrImmBits(unsigned Value) {
126 unsigned lo2 = Value & 0x3;
127 unsigned hi19 = (Value & 0x1ffffc) >> 2;
128 return (hi19 << 5) | (lo2 << 29);
129 }
130
adjustFixupValue(unsigned Kind,uint64_t Value)131 static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
132 int64_t SignedValue = static_cast<int64_t>(Value);
133 switch (Kind) {
134 default:
135 llvm_unreachable("Unknown fixup kind!");
136 case AArch64::fixup_aarch64_pcrel_adr_imm21:
137 if (SignedValue > 2097151 || SignedValue < -2097152)
138 report_fatal_error("fixup value out of range");
139 return AdrImmBits(Value & 0x1fffffULL);
140 case AArch64::fixup_aarch64_pcrel_adrp_imm21:
141 return AdrImmBits((Value & 0x1fffff000ULL) >> 12);
142 case AArch64::fixup_aarch64_ldr_pcrel_imm19:
143 case AArch64::fixup_aarch64_pcrel_branch19:
144 // Signed 21-bit immediate
145 if (SignedValue > 2097151 || SignedValue < -2097152)
146 report_fatal_error("fixup value out of range");
147 // Low two bits are not encoded.
148 return (Value >> 2) & 0x7ffff;
149 case AArch64::fixup_aarch64_add_imm12:
150 case AArch64::fixup_aarch64_ldst_imm12_scale1:
151 // Unsigned 12-bit immediate
152 if (Value >= 0x1000)
153 report_fatal_error("invalid imm12 fixup value");
154 return Value;
155 case AArch64::fixup_aarch64_ldst_imm12_scale2:
156 // Unsigned 12-bit immediate which gets multiplied by 2
157 if (Value & 1 || Value >= 0x2000)
158 report_fatal_error("invalid imm12 fixup value");
159 return Value >> 1;
160 case AArch64::fixup_aarch64_ldst_imm12_scale4:
161 // Unsigned 12-bit immediate which gets multiplied by 4
162 if (Value & 3 || Value >= 0x4000)
163 report_fatal_error("invalid imm12 fixup value");
164 return Value >> 2;
165 case AArch64::fixup_aarch64_ldst_imm12_scale8:
166 // Unsigned 12-bit immediate which gets multiplied by 8
167 if (Value & 7 || Value >= 0x8000)
168 report_fatal_error("invalid imm12 fixup value");
169 return Value >> 3;
170 case AArch64::fixup_aarch64_ldst_imm12_scale16:
171 // Unsigned 12-bit immediate which gets multiplied by 16
172 if (Value & 15 || Value >= 0x10000)
173 report_fatal_error("invalid imm12 fixup value");
174 return Value >> 4;
175 case AArch64::fixup_aarch64_movw:
176 report_fatal_error("no resolvable MOVZ/MOVK fixups supported yet");
177 return Value;
178 case AArch64::fixup_aarch64_pcrel_branch14:
179 // Signed 16-bit immediate
180 if (SignedValue > 32767 || SignedValue < -32768)
181 report_fatal_error("fixup value out of range");
182 // Low two bits are not encoded (4-byte alignment assumed).
183 if (Value & 0x3)
184 report_fatal_error("fixup not sufficiently aligned");
185 return (Value >> 2) & 0x3fff;
186 case AArch64::fixup_aarch64_pcrel_branch26:
187 case AArch64::fixup_aarch64_pcrel_call26:
188 // Signed 28-bit immediate
189 if (SignedValue > 134217727 || SignedValue < -134217728)
190 report_fatal_error("fixup value out of range");
191 // Low two bits are not encoded (4-byte alignment assumed).
192 if (Value & 0x3)
193 report_fatal_error("fixup not sufficiently aligned");
194 return (Value >> 2) & 0x3ffffff;
195 case FK_Data_1:
196 case FK_Data_2:
197 case FK_Data_4:
198 case FK_Data_8:
199 return Value;
200 }
201 }
202
applyFixup(const MCFixup & Fixup,char * Data,unsigned DataSize,uint64_t Value,bool IsPCRel) const203 void AArch64AsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
204 unsigned DataSize, uint64_t Value,
205 bool IsPCRel) const {
206 unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
207 if (!Value)
208 return; // Doesn't change encoding.
209 MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
210 // Apply any target-specific value adjustments.
211 Value = adjustFixupValue(Fixup.getKind(), Value);
212
213 // Shift the value into position.
214 Value <<= Info.TargetOffset;
215
216 unsigned Offset = Fixup.getOffset();
217 assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
218
219 // For each byte of the fragment that the fixup touches, mask in the
220 // bits from the fixup value.
221 for (unsigned i = 0; i != NumBytes; ++i)
222 Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
223 }
224
mayNeedRelaxation(const MCInst & Inst) const225 bool AArch64AsmBackend::mayNeedRelaxation(const MCInst &Inst) const {
226 return false;
227 }
228
fixupNeedsRelaxation(const MCFixup & Fixup,uint64_t Value,const MCRelaxableFragment * DF,const MCAsmLayout & Layout) const229 bool AArch64AsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
230 uint64_t Value,
231 const MCRelaxableFragment *DF,
232 const MCAsmLayout &Layout) const {
233 // FIXME: This isn't correct for AArch64. Just moving the "generic" logic
234 // into the targets for now.
235 //
236 // Relax if the value is too big for a (signed) i8.
237 return int64_t(Value) != int64_t(int8_t(Value));
238 }
239
relaxInstruction(const MCInst & Inst,MCInst & Res) const240 void AArch64AsmBackend::relaxInstruction(const MCInst &Inst,
241 MCInst &Res) const {
242 llvm_unreachable("AArch64AsmBackend::relaxInstruction() unimplemented");
243 }
244
writeNopData(uint64_t Count,MCObjectWriter * OW) const245 bool AArch64AsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
246 // If the count is not 4-byte aligned, we must be writing data into the text
247 // section (otherwise we have unaligned instructions, and thus have far
248 // bigger problems), so just write zeros instead.
249 if ((Count & 3) != 0) {
250 for (uint64_t i = 0, e = (Count & 3); i != e; ++i)
251 OW->Write8(0);
252 }
253
254 // We are properly aligned, so write NOPs as requested.
255 Count /= 4;
256 for (uint64_t i = 0; i != Count; ++i)
257 OW->Write32(0xd503201f);
258 return true;
259 }
260
261 namespace {
262
263 namespace CU {
264
265 /// \brief Compact unwind encoding values.
266 enum CompactUnwindEncodings {
267 /// \brief A "frameless" leaf function, where no non-volatile registers are
268 /// saved. The return remains in LR throughout the function.
269 UNWIND_AArch64_MODE_FRAMELESS = 0x02000000,
270
271 /// \brief No compact unwind encoding available. Instead the low 23-bits of
272 /// the compact unwind encoding is the offset of the DWARF FDE in the
273 /// __eh_frame section. This mode is never used in object files. It is only
274 /// generated by the linker in final linked images, which have only DWARF info
275 /// for a function.
276 UNWIND_AArch64_MODE_DWARF = 0x03000000,
277
278 /// \brief This is a standard arm64 prologue where FP/LR are immediately
279 /// pushed on the stack, then SP is copied to FP. If there are any
280 /// non-volatile register saved, they are copied into the stack fame in pairs
281 /// in a contiguous ranger right below the saved FP/LR pair. Any subset of the
282 /// five X pairs and four D pairs can be saved, but the memory layout must be
283 /// in register number order.
284 UNWIND_AArch64_MODE_FRAME = 0x04000000,
285
286 /// \brief Frame register pair encodings.
287 UNWIND_AArch64_FRAME_X19_X20_PAIR = 0x00000001,
288 UNWIND_AArch64_FRAME_X21_X22_PAIR = 0x00000002,
289 UNWIND_AArch64_FRAME_X23_X24_PAIR = 0x00000004,
290 UNWIND_AArch64_FRAME_X25_X26_PAIR = 0x00000008,
291 UNWIND_AArch64_FRAME_X27_X28_PAIR = 0x00000010,
292 UNWIND_AArch64_FRAME_D8_D9_PAIR = 0x00000100,
293 UNWIND_AArch64_FRAME_D10_D11_PAIR = 0x00000200,
294 UNWIND_AArch64_FRAME_D12_D13_PAIR = 0x00000400,
295 UNWIND_AArch64_FRAME_D14_D15_PAIR = 0x00000800
296 };
297
298 } // end CU namespace
299
300 // FIXME: This should be in a separate file.
301 class DarwinAArch64AsmBackend : public AArch64AsmBackend {
302 const MCRegisterInfo &MRI;
303
304 /// \brief Encode compact unwind stack adjustment for frameless functions.
305 /// See UNWIND_AArch64_FRAMELESS_STACK_SIZE_MASK in compact_unwind_encoding.h.
306 /// The stack size always needs to be 16 byte aligned.
encodeStackAdjustment(uint32_t StackSize) const307 uint32_t encodeStackAdjustment(uint32_t StackSize) const {
308 return (StackSize / 16) << 12;
309 }
310
311 public:
DarwinAArch64AsmBackend(const Target & T,const MCRegisterInfo & MRI)312 DarwinAArch64AsmBackend(const Target &T, const MCRegisterInfo &MRI)
313 : AArch64AsmBackend(T), MRI(MRI) {}
314
createObjectWriter(raw_ostream & OS) const315 MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
316 return createAArch64MachObjectWriter(OS, MachO::CPU_TYPE_ARM64,
317 MachO::CPU_SUBTYPE_ARM64_ALL);
318 }
319
doesSectionRequireSymbols(const MCSection & Section) const320 bool doesSectionRequireSymbols(const MCSection &Section) const override {
321 // Any section for which the linker breaks things into atoms needs to
322 // preserve symbols, including assembler local symbols, to identify
323 // those atoms. These sections are:
324 // Sections of type:
325 //
326 // S_CSTRING_LITERALS (e.g. __cstring)
327 // S_LITERAL_POINTERS (e.g. objc selector pointers)
328 // S_16BYTE_LITERALS, S_8BYTE_LITERALS, S_4BYTE_LITERALS
329 //
330 // Sections named:
331 //
332 // __TEXT,__eh_frame
333 // __TEXT,__ustring
334 // __DATA,__cfstring
335 // __DATA,__objc_classrefs
336 // __DATA,__objc_catlist
337 //
338 // FIXME: It would be better if the compiler used actual linker local
339 // symbols for each of these sections rather than preserving what
340 // are ostensibly assembler local symbols.
341 const MCSectionMachO &SMO = static_cast<const MCSectionMachO &>(Section);
342 return (SMO.getType() == MachO::S_CSTRING_LITERALS ||
343 SMO.getType() == MachO::S_4BYTE_LITERALS ||
344 SMO.getType() == MachO::S_8BYTE_LITERALS ||
345 SMO.getType() == MachO::S_16BYTE_LITERALS ||
346 SMO.getType() == MachO::S_LITERAL_POINTERS ||
347 (SMO.getSegmentName() == "__TEXT" &&
348 (SMO.getSectionName() == "__eh_frame" ||
349 SMO.getSectionName() == "__ustring")) ||
350 (SMO.getSegmentName() == "__DATA" &&
351 (SMO.getSectionName() == "__cfstring" ||
352 SMO.getSectionName() == "__objc_classrefs" ||
353 SMO.getSectionName() == "__objc_catlist")));
354 }
355
356 /// \brief Generate the compact unwind encoding from the CFI directives.
generateCompactUnwindEncoding(ArrayRef<MCCFIInstruction> Instrs) const357 uint32_t generateCompactUnwindEncoding(
358 ArrayRef<MCCFIInstruction> Instrs) const override {
359 if (Instrs.empty())
360 return CU::UNWIND_AArch64_MODE_FRAMELESS;
361
362 bool HasFP = false;
363 unsigned StackSize = 0;
364
365 uint32_t CompactUnwindEncoding = 0;
366 for (size_t i = 0, e = Instrs.size(); i != e; ++i) {
367 const MCCFIInstruction &Inst = Instrs[i];
368
369 switch (Inst.getOperation()) {
370 default:
371 // Cannot handle this directive: bail out.
372 return CU::UNWIND_AArch64_MODE_DWARF;
373 case MCCFIInstruction::OpDefCfa: {
374 // Defines a frame pointer.
375 assert(getXRegFromWReg(MRI.getLLVMRegNum(Inst.getRegister(), true)) ==
376 AArch64::FP &&
377 "Invalid frame pointer!");
378 assert(i + 2 < e && "Insufficient CFI instructions to define a frame!");
379
380 const MCCFIInstruction &LRPush = Instrs[++i];
381 assert(LRPush.getOperation() == MCCFIInstruction::OpOffset &&
382 "Link register not pushed!");
383 const MCCFIInstruction &FPPush = Instrs[++i];
384 assert(FPPush.getOperation() == MCCFIInstruction::OpOffset &&
385 "Frame pointer not pushed!");
386
387 unsigned LRReg = MRI.getLLVMRegNum(LRPush.getRegister(), true);
388 unsigned FPReg = MRI.getLLVMRegNum(FPPush.getRegister(), true);
389
390 LRReg = getXRegFromWReg(LRReg);
391 FPReg = getXRegFromWReg(FPReg);
392
393 assert(LRReg == AArch64::LR && FPReg == AArch64::FP &&
394 "Pushing invalid registers for frame!");
395
396 // Indicate that the function has a frame.
397 CompactUnwindEncoding |= CU::UNWIND_AArch64_MODE_FRAME;
398 HasFP = true;
399 break;
400 }
401 case MCCFIInstruction::OpDefCfaOffset: {
402 assert(StackSize == 0 && "We already have the CFA offset!");
403 StackSize = std::abs(Inst.getOffset());
404 break;
405 }
406 case MCCFIInstruction::OpOffset: {
407 // Registers are saved in pairs. We expect there to be two consecutive
408 // `.cfi_offset' instructions with the appropriate registers specified.
409 unsigned Reg1 = MRI.getLLVMRegNum(Inst.getRegister(), true);
410 if (i + 1 == e)
411 return CU::UNWIND_AArch64_MODE_DWARF;
412
413 const MCCFIInstruction &Inst2 = Instrs[++i];
414 if (Inst2.getOperation() != MCCFIInstruction::OpOffset)
415 return CU::UNWIND_AArch64_MODE_DWARF;
416 unsigned Reg2 = MRI.getLLVMRegNum(Inst2.getRegister(), true);
417
418 // N.B. The encodings must be in register number order, and the X
419 // registers before the D registers.
420
421 // X19/X20 pair = 0x00000001,
422 // X21/X22 pair = 0x00000002,
423 // X23/X24 pair = 0x00000004,
424 // X25/X26 pair = 0x00000008,
425 // X27/X28 pair = 0x00000010
426 Reg1 = getXRegFromWReg(Reg1);
427 Reg2 = getXRegFromWReg(Reg2);
428
429 if (Reg1 == AArch64::X19 && Reg2 == AArch64::X20 &&
430 (CompactUnwindEncoding & 0xF1E) == 0)
431 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X19_X20_PAIR;
432 else if (Reg1 == AArch64::X21 && Reg2 == AArch64::X22 &&
433 (CompactUnwindEncoding & 0xF1C) == 0)
434 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X21_X22_PAIR;
435 else if (Reg1 == AArch64::X23 && Reg2 == AArch64::X24 &&
436 (CompactUnwindEncoding & 0xF18) == 0)
437 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X23_X24_PAIR;
438 else if (Reg1 == AArch64::X25 && Reg2 == AArch64::X26 &&
439 (CompactUnwindEncoding & 0xF10) == 0)
440 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X25_X26_PAIR;
441 else if (Reg1 == AArch64::X27 && Reg2 == AArch64::X28 &&
442 (CompactUnwindEncoding & 0xF00) == 0)
443 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X27_X28_PAIR;
444 else {
445 Reg1 = getDRegFromBReg(Reg1);
446 Reg2 = getDRegFromBReg(Reg2);
447
448 // D8/D9 pair = 0x00000100,
449 // D10/D11 pair = 0x00000200,
450 // D12/D13 pair = 0x00000400,
451 // D14/D15 pair = 0x00000800
452 if (Reg1 == AArch64::D8 && Reg2 == AArch64::D9 &&
453 (CompactUnwindEncoding & 0xE00) == 0)
454 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D8_D9_PAIR;
455 else if (Reg1 == AArch64::D10 && Reg2 == AArch64::D11 &&
456 (CompactUnwindEncoding & 0xC00) == 0)
457 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D10_D11_PAIR;
458 else if (Reg1 == AArch64::D12 && Reg2 == AArch64::D13 &&
459 (CompactUnwindEncoding & 0x800) == 0)
460 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D12_D13_PAIR;
461 else if (Reg1 == AArch64::D14 && Reg2 == AArch64::D15)
462 CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D14_D15_PAIR;
463 else
464 // A pair was pushed which we cannot handle.
465 return CU::UNWIND_AArch64_MODE_DWARF;
466 }
467
468 break;
469 }
470 }
471 }
472
473 if (!HasFP) {
474 // With compact unwind info we can only represent stack adjustments of up
475 // to 65520 bytes.
476 if (StackSize > 65520)
477 return CU::UNWIND_AArch64_MODE_DWARF;
478
479 CompactUnwindEncoding |= CU::UNWIND_AArch64_MODE_FRAMELESS;
480 CompactUnwindEncoding |= encodeStackAdjustment(StackSize);
481 }
482
483 return CompactUnwindEncoding;
484 }
485 };
486
487 } // end anonymous namespace
488
489 namespace {
490
491 class ELFAArch64AsmBackend : public AArch64AsmBackend {
492 public:
493 uint8_t OSABI;
494 bool IsLittleEndian;
495
ELFAArch64AsmBackend(const Target & T,uint8_t OSABI,bool IsLittleEndian)496 ELFAArch64AsmBackend(const Target &T, uint8_t OSABI, bool IsLittleEndian)
497 : AArch64AsmBackend(T), OSABI(OSABI), IsLittleEndian(IsLittleEndian) {}
498
createObjectWriter(raw_ostream & OS) const499 MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
500 return createAArch64ELFObjectWriter(OS, OSABI, IsLittleEndian);
501 }
502
503 void processFixupValue(const MCAssembler &Asm, const MCAsmLayout &Layout,
504 const MCFixup &Fixup, const MCFragment *DF,
505 const MCValue &Target, uint64_t &Value,
506 bool &IsResolved) override;
507
508 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
509 uint64_t Value, bool IsPCRel) const override;
510 };
511
processFixupValue(const MCAssembler & Asm,const MCAsmLayout & Layout,const MCFixup & Fixup,const MCFragment * DF,const MCValue & Target,uint64_t & Value,bool & IsResolved)512 void ELFAArch64AsmBackend::processFixupValue(
513 const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFixup &Fixup,
514 const MCFragment *DF, const MCValue &Target, uint64_t &Value,
515 bool &IsResolved) {
516 // The ADRP instruction adds some multiple of 0x1000 to the current PC &
517 // ~0xfff. This means that the required offset to reach a symbol can vary by
518 // up to one step depending on where the ADRP is in memory. For example:
519 //
520 // ADRP x0, there
521 // there:
522 //
523 // If the ADRP occurs at address 0xffc then "there" will be at 0x1000 and
524 // we'll need that as an offset. At any other address "there" will be in the
525 // same page as the ADRP and the instruction should encode 0x0. Assuming the
526 // section isn't 0x1000-aligned, we therefore need to delegate this decision
527 // to the linker -- a relocation!
528 if ((uint32_t)Fixup.getKind() == AArch64::fixup_aarch64_pcrel_adrp_imm21)
529 IsResolved = false;
530 }
531
applyFixup(const MCFixup & Fixup,char * Data,unsigned DataSize,uint64_t Value,bool IsPCRel) const532 void ELFAArch64AsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
533 unsigned DataSize, uint64_t Value,
534 bool IsPCRel) const {
535 // store fixups in .eh_frame section in big endian order
536 if (!IsLittleEndian && Fixup.getKind() == FK_Data_4) {
537 const MCSection *Sec = Fixup.getValue()->FindAssociatedSection();
538 const MCSectionELF *SecELF = dyn_cast_or_null<const MCSectionELF>(Sec);
539 if (SecELF && SecELF->getSectionName() == ".eh_frame")
540 Value = ByteSwap_32(unsigned(Value));
541 }
542 AArch64AsmBackend::applyFixup (Fixup, Data, DataSize, Value, IsPCRel);
543 }
544 }
545
createAArch64leAsmBackend(const Target & T,const MCRegisterInfo & MRI,StringRef TT,StringRef CPU)546 MCAsmBackend *llvm::createAArch64leAsmBackend(const Target &T,
547 const MCRegisterInfo &MRI,
548 StringRef TT, StringRef CPU) {
549 Triple TheTriple(TT);
550
551 if (TheTriple.isOSDarwin())
552 return new DarwinAArch64AsmBackend(T, MRI);
553
554 assert(TheTriple.isOSBinFormatELF() && "Expect either MachO or ELF target");
555 uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
556 return new ELFAArch64AsmBackend(T, OSABI, /*IsLittleEndian=*/true);
557 }
558
createAArch64beAsmBackend(const Target & T,const MCRegisterInfo & MRI,StringRef TT,StringRef CPU)559 MCAsmBackend *llvm::createAArch64beAsmBackend(const Target &T,
560 const MCRegisterInfo &MRI,
561 StringRef TT, StringRef CPU) {
562 Triple TheTriple(TT);
563
564 assert(TheTriple.isOSBinFormatELF() &&
565 "Big endian is only supported for ELF targets!");
566 uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
567 return new ELFAArch64AsmBackend(T, OSABI,
568 /*IsLittleEndian=*/false);
569 }
570