1 //===-- ARMAsmBackend.cpp - ARM Assembler Backend -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "MCTargetDesc/ARMMCTargetDesc.h"
11 #include "MCTargetDesc/ARMBaseInfo.h"
12 #include "MCTargetDesc/ARMFixupKinds.h"
13 #include "MCTargetDesc/ARMAddressingModes.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/MC/MCAssembler.h"
16 #include "llvm/MC/MCDirectives.h"
17 #include "llvm/MC/MCELFObjectWriter.h"
18 #include "llvm/MC/MCExpr.h"
19 #include "llvm/MC/MCMachObjectWriter.h"
20 #include "llvm/MC/MCObjectWriter.h"
21 #include "llvm/MC/MCSectionELF.h"
22 #include "llvm/MC/MCSectionMachO.h"
23 #include "llvm/MC/MCAsmBackend.h"
24 #include "llvm/MC/MCSubtargetInfo.h"
25 #include "llvm/Object/MachOFormat.h"
26 #include "llvm/Support/ELF.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
32 class ARMELFObjectWriter : public MCELFObjectTargetWriter {
34 ARMELFObjectWriter(Triple::OSType OSType)
35 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSType, ELF::EM_ARM,
36 /*HasRelocationAddend*/ false) {}
39 class ARMAsmBackend : public MCAsmBackend {
40 const MCSubtargetInfo* STI;
41 bool isThumbMode; // Currently emitting Thumb code.
43 ARMAsmBackend(const Target &T, const StringRef TT)
44 : MCAsmBackend(), STI(ARM_MC::createARMMCSubtargetInfo(TT, "", "")),
45 isThumbMode(TT.startswith("thumb")) {}
51 unsigned getNumFixupKinds() const { return ARM::NumTargetFixupKinds; }
54 return (STI->getFeatureBits() & ARM::HasV6T2Ops) != 0;
57 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
58 const static MCFixupKindInfo Infos[ARM::NumTargetFixupKinds] = {
59 // This table *must* be in the order that the fixup_* kinds are defined in
62 // Name Offset (bits) Size (bits) Flags
63 { "fixup_arm_ldst_pcrel_12", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
64 { "fixup_t2_ldst_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
65 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
66 { "fixup_arm_pcrel_10", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
67 { "fixup_t2_pcrel_10", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
68 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
69 { "fixup_thumb_adr_pcrel_10",0, 8, MCFixupKindInfo::FKF_IsPCRel |
70 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
71 { "fixup_arm_adr_pcrel_12", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
72 { "fixup_t2_adr_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
73 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
74 { "fixup_arm_condbranch", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
75 { "fixup_arm_uncondbranch", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
76 { "fixup_t2_condbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
77 { "fixup_t2_uncondbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
78 { "fixup_arm_thumb_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
79 { "fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
80 { "fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
81 { "fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
82 { "fixup_arm_thumb_cp", 0, 8, MCFixupKindInfo::FKF_IsPCRel },
83 { "fixup_arm_thumb_bcc", 0, 8, MCFixupKindInfo::FKF_IsPCRel },
84 // movw / movt: 16-bits immediate but scattered into two chunks 0 - 12, 16 - 19.
85 { "fixup_arm_movt_hi16", 0, 20, 0 },
86 { "fixup_arm_movw_lo16", 0, 20, 0 },
87 { "fixup_t2_movt_hi16", 0, 20, 0 },
88 { "fixup_t2_movw_lo16", 0, 20, 0 },
89 { "fixup_arm_movt_hi16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel },
90 { "fixup_arm_movw_lo16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel },
91 { "fixup_t2_movt_hi16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel },
92 { "fixup_t2_movw_lo16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel },
95 if (Kind < FirstTargetFixupKind)
96 return MCAsmBackend::getFixupKindInfo(Kind);
98 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
100 return Infos[Kind - FirstTargetFixupKind];
103 bool MayNeedRelaxation(const MCInst &Inst) const;
105 void RelaxInstruction(const MCInst &Inst, MCInst &Res) const;
107 bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;
109 void HandleAssemblerFlag(MCAssemblerFlag Flag) {
121 unsigned getPointerSize() const { return 4; }
122 bool isThumb() const { return isThumbMode; }
123 void setIsThumb(bool it) { isThumbMode = it; }
125 } // end anonymous namespace
127 bool ARMAsmBackend::MayNeedRelaxation(const MCInst &Inst) const {
128 // FIXME: Thumb targets, different move constant targets..
132 void ARMAsmBackend::RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
133 assert(0 && "ARMAsmBackend::RelaxInstruction() unimplemented");
137 bool ARMAsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
138 const uint16_t Thumb1_16bitNopEncoding = 0x46c0; // using MOV r8,r8
139 const uint16_t Thumb2_16bitNopEncoding = 0xbf00; // NOP
140 const uint32_t ARMv4_NopEncoding = 0xe1a0000; // using MOV r0,r0
141 const uint32_t ARMv6T2_NopEncoding = 0xe3207800; // NOP
143 const uint16_t nopEncoding = hasNOP() ? Thumb2_16bitNopEncoding
144 : Thumb1_16bitNopEncoding;
145 uint64_t NumNops = Count / 2;
146 for (uint64_t i = 0; i != NumNops; ++i)
147 OW->Write16(nopEncoding);
153 const uint32_t nopEncoding = hasNOP() ? ARMv6T2_NopEncoding
155 uint64_t NumNops = Count / 4;
156 for (uint64_t i = 0; i != NumNops; ++i)
157 OW->Write32(nopEncoding);
158 // FIXME: should this function return false when unable to write exactly
159 // 'Count' bytes with NOP encodings?
161 default: break; // No leftover bytes to write
162 case 1: OW->Write8(0); break;
163 case 2: OW->Write16(0); break;
164 case 3: OW->Write16(0); OW->Write8(0xa0); break;
170 static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
173 llvm_unreachable("Unknown fixup kind!");
178 case ARM::fixup_arm_movt_hi16:
181 case ARM::fixup_arm_movw_lo16:
182 case ARM::fixup_arm_movt_hi16_pcrel:
183 case ARM::fixup_arm_movw_lo16_pcrel: {
184 unsigned Hi4 = (Value & 0xF000) >> 12;
185 unsigned Lo12 = Value & 0x0FFF;
186 // inst{19-16} = Hi4;
187 // inst{11-0} = Lo12;
188 Value = (Hi4 << 16) | (Lo12);
191 case ARM::fixup_t2_movt_hi16:
194 case ARM::fixup_t2_movw_lo16:
195 case ARM::fixup_t2_movt_hi16_pcrel: //FIXME: Shouldn't this be shifted like
196 // the other hi16 fixup?
197 case ARM::fixup_t2_movw_lo16_pcrel: {
198 unsigned Hi4 = (Value & 0xF000) >> 12;
199 unsigned i = (Value & 0x800) >> 11;
200 unsigned Mid3 = (Value & 0x700) >> 8;
201 unsigned Lo8 = Value & 0x0FF;
202 // inst{19-16} = Hi4;
204 // inst{14-12} = Mid3;
206 uint64_t swapped = (Value & 0xFFFF0000) >> 16;
207 swapped |= (Value & 0x0000FFFF) << 16;
210 case ARM::fixup_arm_ldst_pcrel_12:
211 // ARM PC-relative values are offset by 8.
214 case ARM::fixup_t2_ldst_pcrel_12: {
215 // Offset by 4, adjusted by two due to the half-word ordering of thumb.
218 if ((int64_t)Value < 0) {
222 assert ((Value < 4096) && "Out of range pc-relative fixup value!");
223 Value |= isAdd << 23;
225 // Same addressing mode as fixup_arm_pcrel_10,
226 // but with 16-bit halfwords swapped.
227 if (Kind == ARM::fixup_t2_ldst_pcrel_12) {
228 uint64_t swapped = (Value & 0xFFFF0000) >> 16;
229 swapped |= (Value & 0x0000FFFF) << 16;
235 case ARM::fixup_thumb_adr_pcrel_10:
236 return ((Value - 4) >> 2) & 0xff;
237 case ARM::fixup_arm_adr_pcrel_12: {
238 // ARM PC-relative values are offset by 8.
240 unsigned opc = 4; // bits {24-21}. Default to add: 0b0100
241 if ((int64_t)Value < 0) {
245 assert(ARM_AM::getSOImmVal(Value) != -1 &&
246 "Out of range pc-relative fixup value!");
247 // Encode the immediate and shift the opcode into place.
248 return ARM_AM::getSOImmVal(Value) | (opc << 21);
251 case ARM::fixup_t2_adr_pcrel_12: {
254 if ((int64_t)Value < 0) {
259 uint32_t out = (opc << 21);
260 out |= (Value & 0x800) << 15;
261 out |= (Value & 0x700) << 4;
262 out |= (Value & 0x0FF);
264 uint64_t swapped = (out & 0xFFFF0000) >> 16;
265 swapped |= (out & 0x0000FFFF) << 16;
269 case ARM::fixup_arm_condbranch:
270 case ARM::fixup_arm_uncondbranch:
271 // These values don't encode the low two bits since they're always zero.
272 // Offset by 8 just as above.
273 return 0xffffff & ((Value - 8) >> 2);
274 case ARM::fixup_t2_uncondbranch: {
276 Value >>= 1; // Low bit is not encoded.
279 bool I = Value & 0x800000;
280 bool J1 = Value & 0x400000;
281 bool J2 = Value & 0x200000;
285 out |= I << 26; // S bit
286 out |= !J1 << 13; // J1 bit
287 out |= !J2 << 11; // J2 bit
288 out |= (Value & 0x1FF800) << 5; // imm6 field
289 out |= (Value & 0x0007FF); // imm11 field
291 uint64_t swapped = (out & 0xFFFF0000) >> 16;
292 swapped |= (out & 0x0000FFFF) << 16;
295 case ARM::fixup_t2_condbranch: {
297 Value >>= 1; // Low bit is not encoded.
300 out |= (Value & 0x80000) << 7; // S bit
301 out |= (Value & 0x40000) >> 7; // J2 bit
302 out |= (Value & 0x20000) >> 4; // J1 bit
303 out |= (Value & 0x1F800) << 5; // imm6 field
304 out |= (Value & 0x007FF); // imm11 field
306 uint32_t swapped = (out & 0xFFFF0000) >> 16;
307 swapped |= (out & 0x0000FFFF) << 16;
310 case ARM::fixup_arm_thumb_bl: {
311 // The value doesn't encode the low bit (always zero) and is offset by
312 // four. The value is encoded into disjoint bit positions in the destination
313 // opcode. x = unchanged, I = immediate value bit, S = sign extension bit
315 // BL: xxxxxSIIIIIIIIII xxxxxIIIIIIIIIII
317 // Note that the halfwords are stored high first, low second; so we need
318 // to transpose the fixup value here to map properly.
319 unsigned isNeg = (int64_t(Value - 4) < 0) ? 1 : 0;
321 Value = 0x3fffff & ((Value - 4) >> 1);
322 Binary = (Value & 0x7ff) << 16; // Low imm11 value.
323 Binary |= (Value & 0x1ffc00) >> 11; // High imm10 value.
324 Binary |= isNeg << 10; // Sign bit.
327 case ARM::fixup_arm_thumb_blx: {
328 // The value doesn't encode the low two bits (always zero) and is offset by
329 // four (see fixup_arm_thumb_cp). The value is encoded into disjoint bit
330 // positions in the destination opcode. x = unchanged, I = immediate value
331 // bit, S = sign extension bit, 0 = zero.
333 // BLX: xxxxxSIIIIIIIIII xxxxxIIIIIIIIII0
335 // Note that the halfwords are stored high first, low second; so we need
336 // to transpose the fixup value here to map properly.
337 unsigned isNeg = (int64_t(Value-4) < 0) ? 1 : 0;
339 Value = 0xfffff & ((Value - 2) >> 2);
340 Binary = (Value & 0x3ff) << 17; // Low imm10L value.
341 Binary |= (Value & 0xffc00) >> 10; // High imm10H value.
342 Binary |= isNeg << 10; // Sign bit.
345 case ARM::fixup_arm_thumb_cp:
346 // Offset by 4, and don't encode the low two bits. Two bytes of that
347 // 'off by 4' is implicitly handled by the half-word ordering of the
348 // Thumb encoding, so we only need to adjust by 2 here.
349 return ((Value - 2) >> 2) & 0xff;
350 case ARM::fixup_arm_thumb_cb: {
351 // Offset by 4 and don't encode the lower bit, which is always 0.
352 uint32_t Binary = (Value - 4) >> 1;
353 return ((Binary & 0x20) << 4) | ((Binary & 0x1f) << 3);
355 case ARM::fixup_arm_thumb_br:
356 // Offset by 4 and don't encode the lower bit, which is always 0.
357 return ((Value - 4) >> 1) & 0x7ff;
358 case ARM::fixup_arm_thumb_bcc:
359 // Offset by 4 and don't encode the lower bit, which is always 0.
360 return ((Value - 4) >> 1) & 0xff;
361 case ARM::fixup_arm_pcrel_10:
362 Value = Value - 4; // ARM fixups offset by an additional word and don't
363 // need to adjust for the half-word ordering.
365 case ARM::fixup_t2_pcrel_10: {
366 // Offset by 4, adjusted by two due to the half-word ordering of thumb.
369 if ((int64_t)Value < 0) {
373 // These values don't encode the low two bits since they're always zero.
375 assert ((Value < 256) && "Out of range pc-relative fixup value!");
376 Value |= isAdd << 23;
378 // Same addressing mode as fixup_arm_pcrel_10,
379 // but with 16-bit halfwords swapped.
380 if (Kind == ARM::fixup_t2_pcrel_10) {
381 uint32_t swapped = (Value & 0xFFFF0000) >> 16;
382 swapped |= (Value & 0x0000FFFF) << 16;
393 // FIXME: This should be in a separate file.
394 // ELF is an ELF of course...
395 class ELFARMAsmBackend : public ARMAsmBackend {
397 Triple::OSType OSType;
398 ELFARMAsmBackend(const Target &T, const StringRef TT,
399 Triple::OSType _OSType)
400 : ARMAsmBackend(T, TT), OSType(_OSType) { }
402 void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
403 uint64_t Value) const;
405 MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
406 return createELFObjectWriter(new ARMELFObjectWriter(OSType), OS,
407 /*IsLittleEndian*/ true);
411 // FIXME: Raise this to share code between Darwin and ELF.
412 void ELFARMAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data,
413 unsigned DataSize, uint64_t Value) const {
414 unsigned NumBytes = 4; // FIXME: 2 for Thumb
415 Value = adjustFixupValue(Fixup.getKind(), Value);
416 if (!Value) return; // Doesn't change encoding.
418 unsigned Offset = Fixup.getOffset();
420 // For each byte of the fragment that the fixup touches, mask in the bits from
421 // the fixup value. The Value has been "split up" into the appropriate
423 for (unsigned i = 0; i != NumBytes; ++i)
424 Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
427 // FIXME: This should be in a separate file.
428 class DarwinARMAsmBackend : public ARMAsmBackend {
430 const object::mach::CPUSubtypeARM Subtype;
431 DarwinARMAsmBackend(const Target &T, const StringRef TT,
432 object::mach::CPUSubtypeARM st)
433 : ARMAsmBackend(T, TT), Subtype(st) { }
435 MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
436 return createARMMachObjectWriter(OS, /*Is64Bit=*/false,
437 object::mach::CTM_ARM,
441 void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
442 uint64_t Value) const;
444 virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
449 /// getFixupKindNumBytes - The number of bytes the fixup may change.
450 static unsigned getFixupKindNumBytes(unsigned Kind) {
453 llvm_unreachable("Unknown fixup kind!");
456 case ARM::fixup_arm_thumb_bcc:
457 case ARM::fixup_arm_thumb_cp:
458 case ARM::fixup_thumb_adr_pcrel_10:
462 case ARM::fixup_arm_thumb_br:
463 case ARM::fixup_arm_thumb_cb:
466 case ARM::fixup_arm_ldst_pcrel_12:
467 case ARM::fixup_arm_pcrel_10:
468 case ARM::fixup_arm_adr_pcrel_12:
469 case ARM::fixup_arm_condbranch:
470 case ARM::fixup_arm_uncondbranch:
474 case ARM::fixup_t2_ldst_pcrel_12:
475 case ARM::fixup_t2_condbranch:
476 case ARM::fixup_t2_uncondbranch:
477 case ARM::fixup_t2_pcrel_10:
478 case ARM::fixup_t2_adr_pcrel_12:
479 case ARM::fixup_arm_thumb_bl:
480 case ARM::fixup_arm_thumb_blx:
481 case ARM::fixup_arm_movt_hi16:
482 case ARM::fixup_arm_movw_lo16:
483 case ARM::fixup_arm_movt_hi16_pcrel:
484 case ARM::fixup_arm_movw_lo16_pcrel:
485 case ARM::fixup_t2_movt_hi16:
486 case ARM::fixup_t2_movw_lo16:
487 case ARM::fixup_t2_movt_hi16_pcrel:
488 case ARM::fixup_t2_movw_lo16_pcrel:
493 void DarwinARMAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data,
494 unsigned DataSize, uint64_t Value) const {
495 unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
496 Value = adjustFixupValue(Fixup.getKind(), Value);
497 if (!Value) return; // Doesn't change encoding.
499 unsigned Offset = Fixup.getOffset();
500 assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
502 // For each byte of the fragment that the fixup touches, mask in the
503 // bits from the fixup value.
504 for (unsigned i = 0; i != NumBytes; ++i)
505 Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
508 } // end anonymous namespace
510 MCAsmBackend *llvm::createARMAsmBackend(const Target &T, StringRef TT) {
511 Triple TheTriple(TT);
513 if (TheTriple.isOSDarwin()) {
514 if (TheTriple.getArchName() == "armv4t" ||
515 TheTriple.getArchName() == "thumbv4t")
516 return new DarwinARMAsmBackend(T, TT, object::mach::CSARM_V4T);
517 else if (TheTriple.getArchName() == "armv5e" ||
518 TheTriple.getArchName() == "thumbv5e")
519 return new DarwinARMAsmBackend(T, TT, object::mach::CSARM_V5TEJ);
520 else if (TheTriple.getArchName() == "armv6" ||
521 TheTriple.getArchName() == "thumbv6")
522 return new DarwinARMAsmBackend(T, TT, object::mach::CSARM_V6);
523 return new DarwinARMAsmBackend(T, TT, object::mach::CSARM_V7);
526 if (TheTriple.isOSWindows())
527 assert(0 && "Windows not supported on ARM");
529 return new ELFARMAsmBackend(T, TT, Triple(TT).getOS());