1 //===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
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 #define DEBUG_TYPE "assembler"
11 #include "llvm/MC/MCAssembler.h"
12 #include "llvm/MC/MCAsmLayout.h"
13 #include "llvm/MC/MCCodeEmitter.h"
14 #include "llvm/MC/MCExpr.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/MC/MCSymbol.h"
17 #include "llvm/MC/MCValue.h"
18 #include "llvm/ADT/OwningPtr.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/ADT/StringExtras.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include "llvm/Target/TargetRegistry.h"
26 #include "llvm/Target/TargetAsmBackend.h"
33 STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
34 STATISTIC(EvaluateFixup, "Number of evaluated fixups");
35 STATISTIC(FragmentLayouts, "Number of fragment layouts");
36 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
37 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
38 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
39 STATISTIC(SectionLayouts, "Number of section layouts");
43 // FIXME FIXME FIXME: There are number of places in this file where we convert
44 // what is a 64-bit assembler value used for computation into a value in the
45 // object file, which may truncate it. We should detect that truncation where
46 // invalid and report errors back.
50 MCAsmLayout::MCAsmLayout(MCAssembler &Asm) : Assembler(Asm) {
51 // Compute the section layout order. Virtual sections must go last.
52 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
53 if (!Asm.getBackend().isVirtualSection(it->getSection()))
54 SectionOrder.push_back(&*it);
55 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
56 if (Asm.getBackend().isVirtualSection(it->getSection()))
57 SectionOrder.push_back(&*it);
60 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
61 // We shouldn't have to do anything special to support negative slides, and it
62 // is a perfectly valid thing to do as long as other parts of the system can
63 // guarantee convergence.
64 assert(SlideAmount >= 0 && "Negative slides not yet supported");
66 // Update the layout by simply recomputing the layout for the entire
67 // file. This is trivially correct, but very slow.
69 // FIXME-PERF: This is O(N^2), but will be eliminated once we get smarter.
71 // Layout the sections in order.
72 for (unsigned i = 0, e = getSectionOrder().size(); i != e; ++i)
73 getAssembler().LayoutSection(*this, i);
76 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
77 assert(F->getParent() && "Missing section()!");
78 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
81 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
82 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
83 return F->EffectiveSize;
86 void MCAsmLayout::setFragmentEffectiveSize(MCFragment *F, uint64_t Value) {
87 F->EffectiveSize = Value;
90 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
91 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
95 void MCAsmLayout::setFragmentOffset(MCFragment *F, uint64_t Value) {
99 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
100 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
101 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
104 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
105 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
109 void MCAsmLayout::setSectionAddress(MCSectionData *SD, uint64_t Value) {
113 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
114 assert(SD->Size != ~UINT64_C(0) && "File size not set!");
117 void MCAsmLayout::setSectionSize(MCSectionData *SD, uint64_t Value) {
121 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
122 assert(SD->FileSize != ~UINT64_C(0) && "File size not set!");
125 void MCAsmLayout::setSectionFileSize(MCSectionData *SD, uint64_t Value) {
126 SD->FileSize = Value;
131 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
134 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
135 : Kind(_Kind), Parent(_Parent), Atom(0), EffectiveSize(~UINT64_C(0))
138 Parent->getFragmentList().push_back(this);
141 MCFragment::~MCFragment() {
146 MCSectionData::MCSectionData() : Section(0) {}
148 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
149 : Section(&_Section),
151 Address(~UINT64_C(0)),
153 FileSize(~UINT64_C(0)),
154 HasInstructions(false)
157 A->getSectionList().push_back(this);
162 MCSymbolData::MCSymbolData() : Symbol(0) {}
164 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
165 uint64_t _Offset, MCAssembler *A)
166 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
167 IsExternal(false), IsPrivateExtern(false),
168 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
171 A->getSymbolList().push_back(this);
176 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
177 MCCodeEmitter &_Emitter, raw_ostream &_OS)
178 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
179 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
183 MCAssembler::~MCAssembler() {
186 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
187 const MCAsmFixup &Fixup,
188 const MCValue Target,
189 const MCSection *BaseSection) {
190 // The effective fixup address is
191 // addr(atom(A)) + offset(A)
192 // - addr(atom(B)) - offset(B)
193 // - addr(<base symbol>) + <fixup offset from base symbol>
194 // and the offsets are not relocatable, so the fixup is fully resolved when
195 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
197 // The simple (Darwin, except on x86_64) way of dealing with this was to
198 // assume that any reference to a temporary symbol *must* be a temporary
199 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
200 // relocation to a temporary symbol (in the same section) is fully
201 // resolved. This also works in conjunction with absolutized .set, which
202 // requires the compiler to use .set to absolutize the differences between
203 // symbols which the compiler knows to be assembly time constants, so we don't
204 // need to worry about considering symbol differences fully resolved.
206 // Non-relative fixups are only resolved if constant.
208 return Target.isAbsolute();
210 // Otherwise, relative fixups are only resolved if not a difference and the
211 // target is a temporary in the same section.
212 if (Target.isAbsolute() || Target.getSymB())
215 const MCSymbol *A = &Target.getSymA()->getSymbol();
216 if (!A->isTemporary() || !A->isInSection() ||
217 &A->getSection() != BaseSection)
223 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
224 const MCAsmLayout &Layout,
225 const MCAsmFixup &Fixup,
226 const MCValue Target,
227 const MCSymbolData *BaseSymbol) {
228 // The effective fixup address is
229 // addr(atom(A)) + offset(A)
230 // - addr(atom(B)) - offset(B)
231 // - addr(BaseSymbol) + <fixup offset from base symbol>
232 // and the offsets are not relocatable, so the fixup is fully resolved when
233 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
235 // Note that "false" is almost always conservatively correct (it means we emit
236 // a relocation which is unnecessary), except when it would force us to emit a
237 // relocation which the target cannot encode.
239 const MCSymbolData *A_Base = 0, *B_Base = 0;
240 if (const MCSymbolRefExpr *A = Target.getSymA()) {
241 // Modified symbol references cannot be resolved.
242 if (A->getKind() != MCSymbolRefExpr::VK_None)
245 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
250 if (const MCSymbolRefExpr *B = Target.getSymB()) {
251 // Modified symbol references cannot be resolved.
252 if (B->getKind() != MCSymbolRefExpr::VK_None)
255 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
260 // If there is no base, A and B have to be the same atom for this fixup to be
263 return A_Base == B_Base;
265 // Otherwise, B must be missing and A must be the base.
266 return !B_Base && BaseSymbol == A_Base;
269 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
270 // Non-temporary labels should always be visible to the linker.
271 if (!SD->getSymbol().isTemporary())
274 // Absolute temporary labels are never visible.
275 if (!SD->getFragment())
278 // Otherwise, check if the section requires symbols even for temporary labels.
279 return getBackend().doesSectionRequireSymbols(
280 SD->getFragment()->getParent()->getSection());
283 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
284 const MCSymbolData *SD) const {
285 // Linker visible symbols define atoms.
286 if (isSymbolLinkerVisible(SD))
289 // Absolute and undefined symbols have no defining atom.
290 if (!SD->getFragment())
293 // Non-linker visible symbols in sections which can't be atomized have no
295 if (!getBackend().isSectionAtomizable(
296 SD->getFragment()->getParent()->getSection()))
299 // Otherwise, return the atom for the containing fragment.
300 return SD->getFragment()->getAtom();
303 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
304 const MCAsmFixup &Fixup, const MCFragment *DF,
305 MCValue &Target, uint64_t &Value) const {
306 ++stats::EvaluateFixup;
308 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
309 report_fatal_error("expected relocatable expression");
311 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
312 // doesn't support small relocations, but then under what criteria does the
313 // assembler allow symbol differences?
315 Value = Target.getConstant();
318 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
319 bool IsResolved = true;
320 if (const MCSymbolRefExpr *A = Target.getSymA()) {
321 if (A->getSymbol().isDefined())
322 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
326 if (const MCSymbolRefExpr *B = Target.getSymB()) {
327 if (B->getSymbol().isDefined())
328 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
333 // If we are using scattered symbols, determine whether this value is actually
334 // resolved; scattering may cause atoms to move.
335 if (IsResolved && getBackend().hasScatteredSymbols()) {
336 if (getBackend().hasReliableSymbolDifference()) {
337 // If this is a PCrel relocation, find the base atom (identified by its
338 // symbol) that the fixup value is relative to.
339 const MCSymbolData *BaseSymbol = 0;
341 BaseSymbol = DF->getAtom();
347 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
350 const MCSection *BaseSection = 0;
352 BaseSection = &DF->getParent()->getSection();
354 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
360 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
365 void MCAssembler::LayoutFragment(MCAsmLayout &Layout, MCFragment &F) {
366 uint64_t StartAddress = Layout.getSectionAddress(F.getParent());
368 // Get the fragment start address.
369 uint64_t Address = StartAddress;
370 MCSectionData::iterator it = &F;
371 if (MCFragment *Prev = F.getPrevNode())
372 Address = (StartAddress + Layout.getFragmentOffset(Prev) +
373 Layout.getFragmentEffectiveSize(Prev));
375 ++stats::FragmentLayouts;
377 uint64_t FragmentOffset = Address - StartAddress;
378 Layout.setFragmentOffset(&F, FragmentOffset);
380 // Evaluate fragment size.
381 uint64_t EffectiveSize = 0;
382 switch (F.getKind()) {
383 case MCFragment::FT_Align: {
384 MCAlignFragment &AF = cast<MCAlignFragment>(F);
386 EffectiveSize = OffsetToAlignment(Address, AF.getAlignment());
387 if (EffectiveSize > AF.getMaxBytesToEmit())
392 case MCFragment::FT_Data:
393 EffectiveSize = cast<MCDataFragment>(F).getContents().size();
396 case MCFragment::FT_Fill: {
397 MCFillFragment &FF = cast<MCFillFragment>(F);
398 EffectiveSize = FF.getSize();
402 case MCFragment::FT_Inst:
403 EffectiveSize = cast<MCInstFragment>(F).getInstSize();
406 case MCFragment::FT_Org: {
407 MCOrgFragment &OF = cast<MCOrgFragment>(F);
409 int64_t TargetLocation;
410 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
411 report_fatal_error("expected assembly-time absolute expression");
413 // FIXME: We need a way to communicate this error.
414 int64_t Offset = TargetLocation - FragmentOffset;
416 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
417 "' (at offset '" + Twine(FragmentOffset) + "'");
419 EffectiveSize = Offset;
423 case MCFragment::FT_ZeroFill: {
424 EffectiveSize = cast<MCZeroFillFragment>(F).getSize();
429 Layout.setFragmentEffectiveSize(&F, EffectiveSize);
432 void MCAssembler::LayoutSection(MCAsmLayout &Layout,
433 unsigned SectionOrderIndex) {
434 MCSectionData &SD = *Layout.getSectionOrder()[SectionOrderIndex];
435 bool IsVirtual = getBackend().isVirtualSection(SD.getSection());
437 ++stats::SectionLayouts;
439 // Get the section start address.
440 uint64_t StartAddress = 0;
441 if (SectionOrderIndex) {
442 MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
443 StartAddress = Layout.getSectionAddress(Prev) + Layout.getSectionSize(Prev);
446 // Align this section if necessary by adding padding bytes to the previous
447 // section. It is safe to adjust this out-of-band, because no symbol or
448 // fragment is allowed to point past the end of the section at any time.
449 if (uint64_t Pad = OffsetToAlignment(StartAddress, SD.getAlignment())) {
450 // Unless this section is virtual (where we are allowed to adjust the offset
451 // freely), the padding goes in the previous section.
453 assert(SectionOrderIndex && "Invalid initial section address!");
454 MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
455 Layout.setSectionFileSize(Prev, Layout.getSectionFileSize(Prev) + Pad);
461 // Set the aligned section address.
462 Layout.setSectionAddress(&SD, StartAddress);
464 for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it)
465 LayoutFragment(Layout, *it);
467 // Set the section sizes.
469 if (!SD.getFragmentList().empty()) {
470 MCFragment *F = &SD.getFragmentList().back();
471 Size = Layout.getFragmentOffset(F) + Layout.getFragmentEffectiveSize(F);
473 Layout.setSectionSize(&SD, Size);
474 Layout.setSectionFileSize(&SD, IsVirtual ? 0 : Size);
477 /// WriteFragmentData - Write the \arg F data to the output file.
478 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
479 const MCFragment &F, MCObjectWriter *OW) {
480 uint64_t Start = OW->getStream().tell();
483 ++stats::EmittedFragments;
485 // FIXME: Embed in fragments instead?
486 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
487 switch (F.getKind()) {
488 case MCFragment::FT_Align: {
489 MCAlignFragment &AF = cast<MCAlignFragment>(F);
490 uint64_t Count = FragmentSize / AF.getValueSize();
492 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
494 // FIXME: This error shouldn't actually occur (the front end should emit
495 // multiple .align directives to enforce the semantics it wants), but is
496 // severe enough that we want to report it. How to handle this?
497 if (Count * AF.getValueSize() != FragmentSize)
498 report_fatal_error("undefined .align directive, value size '" +
499 Twine(AF.getValueSize()) +
500 "' is not a divisor of padding size '" +
501 Twine(FragmentSize) + "'");
503 // See if we are aligning with nops, and if so do that first to try to fill
504 // the Count bytes. Then if that did not fill any bytes or there are any
505 // bytes left to fill use the the Value and ValueSize to fill the rest.
506 // If we are aligning with nops, ask that target to emit the right data.
507 if (AF.getEmitNops()) {
508 if (!Asm.getBackend().WriteNopData(Count, OW))
509 report_fatal_error("unable to write nop sequence of " +
510 Twine(Count) + " bytes");
514 // Otherwise, write out in multiples of the value size.
515 for (uint64_t i = 0; i != Count; ++i) {
516 switch (AF.getValueSize()) {
518 assert(0 && "Invalid size!");
519 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
520 case 2: OW->Write16(uint16_t(AF.getValue())); break;
521 case 4: OW->Write32(uint32_t(AF.getValue())); break;
522 case 8: OW->Write64(uint64_t(AF.getValue())); break;
528 case MCFragment::FT_Data: {
529 MCDataFragment &DF = cast<MCDataFragment>(F);
530 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
531 OW->WriteBytes(DF.getContents().str());
535 case MCFragment::FT_Fill: {
536 MCFillFragment &FF = cast<MCFillFragment>(F);
538 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
540 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
541 switch (FF.getValueSize()) {
543 assert(0 && "Invalid size!");
544 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
545 case 2: OW->Write16(uint16_t(FF.getValue())); break;
546 case 4: OW->Write32(uint32_t(FF.getValue())); break;
547 case 8: OW->Write64(uint64_t(FF.getValue())); break;
553 case MCFragment::FT_Inst:
554 llvm_unreachable("unexpected inst fragment after lowering");
557 case MCFragment::FT_Org: {
558 MCOrgFragment &OF = cast<MCOrgFragment>(F);
560 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
561 OW->Write8(uint8_t(OF.getValue()));
566 case MCFragment::FT_ZeroFill: {
567 assert(0 && "Invalid zero fill fragment in concrete section!");
572 assert(OW->getStream().tell() - Start == FragmentSize);
575 void MCAssembler::WriteSectionData(const MCSectionData *SD,
576 const MCAsmLayout &Layout,
577 MCObjectWriter *OW) const {
578 uint64_t SectionSize = Layout.getSectionSize(SD);
579 uint64_t SectionFileSize = Layout.getSectionFileSize(SD);
581 // Ignore virtual sections.
582 if (getBackend().isVirtualSection(SD->getSection())) {
583 assert(SectionFileSize == 0 && "Invalid size for section!");
585 // Check that contents are only things legal inside a virtual section.
586 for (MCSectionData::const_iterator it = SD->begin(),
587 ie = SD->end(); it != ie; ++it) {
588 switch (it->getKind()) {
590 assert(0 && "Invalid fragment in virtual section!");
591 case MCFragment::FT_Align:
592 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
593 "Invalid align in virtual section!");
595 case MCFragment::FT_Fill:
596 assert(!cast<MCFillFragment>(it)->getValueSize() &&
597 "Invalid fill in virtual section!");
599 case MCFragment::FT_ZeroFill:
607 uint64_t Start = OW->getStream().tell();
610 for (MCSectionData::const_iterator it = SD->begin(),
611 ie = SD->end(); it != ie; ++it)
612 WriteFragmentData(*this, Layout, *it, OW);
614 // Add section padding.
615 assert(SectionFileSize >= SectionSize && "Invalid section sizes!");
616 OW->WriteZeros(SectionFileSize - SectionSize);
618 assert(OW->getStream().tell() - Start == SectionFileSize);
621 void MCAssembler::Finish() {
622 DEBUG_WITH_TYPE("mc-dump", {
623 llvm::errs() << "assembler backend - pre-layout\n--\n";
626 // Assign section and fragment ordinals, all subsequent backend code is
627 // responsible for updating these in place.
628 unsigned SectionIndex = 0;
629 unsigned FragmentIndex = 0;
630 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
631 it->setOrdinal(SectionIndex++);
633 for (MCSectionData::iterator it2 = it->begin(),
634 ie2 = it->end(); it2 != ie2; ++it2)
635 it2->setOrdinal(FragmentIndex++);
638 // Layout until everything fits.
639 MCAsmLayout Layout(*this);
640 while (LayoutOnce(Layout))
643 DEBUG_WITH_TYPE("mc-dump", {
644 llvm::errs() << "assembler backend - post-relaxation\n--\n";
647 // Finalize the layout, including fragment lowering.
648 FinishLayout(Layout);
650 DEBUG_WITH_TYPE("mc-dump", {
651 llvm::errs() << "assembler backend - final-layout\n--\n";
654 uint64_t StartOffset = OS.tell();
655 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
657 report_fatal_error("unable to create object writer!");
659 // Allow the object writer a chance to perform post-layout binding (for
660 // example, to set the index fields in the symbol data).
661 Writer->ExecutePostLayoutBinding(*this);
663 // Evaluate and apply the fixups, generating relocation entries as necessary.
664 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
665 for (MCSectionData::iterator it2 = it->begin(),
666 ie2 = it->end(); it2 != ie2; ++it2) {
667 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
671 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
672 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
673 MCAsmFixup &Fixup = *it3;
675 // Evaluate the fixup.
678 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
679 // The fixup was unresolved, we need a relocation. Inform the object
680 // writer of the relocation, and give it an opportunity to adjust the
681 // fixup value if need be.
682 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
685 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
690 // Write the object file.
691 Writer->WriteObject(*this, Layout);
694 stats::ObjectBytes += OS.tell() - StartOffset;
697 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &Fixup,
698 const MCFragment *DF,
699 const MCAsmLayout &Layout) const {
703 // If we cannot resolve the fixup value, it requires relaxation.
706 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
709 // Otherwise, relax if the value is too big for a (signed) i8.
711 // FIXME: This is target dependent!
712 return int64_t(Value) != int64_t(int8_t(Value));
715 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
716 const MCAsmLayout &Layout) const {
717 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
718 // are intentionally pushing out inst fragments, or because we relaxed a
719 // previous instruction to one that doesn't need relaxation.
720 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
723 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
724 ie = IF->fixup_end(); it != ie; ++it)
725 if (FixupNeedsRelaxation(*it, IF, Layout))
731 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
732 ++stats::RelaxationSteps;
734 // Layout the sections in order.
735 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i)
736 LayoutSection(Layout, i);
738 // Scan for fragments that need relaxation.
739 bool WasRelaxed = false;
740 for (iterator it = begin(), ie = end(); it != ie; ++it) {
741 MCSectionData &SD = *it;
743 for (MCSectionData::iterator it2 = SD.begin(),
744 ie2 = SD.end(); it2 != ie2; ++it2) {
745 // Check if this is an instruction fragment that needs relaxation.
746 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
747 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
750 ++stats::RelaxedInstructions;
752 // FIXME-PERF: We could immediately lower out instructions if we can tell
753 // they are fully resolved, to avoid retesting on later passes.
755 // Relax the fragment.
758 getBackend().RelaxInstruction(IF, Relaxed);
760 // Encode the new instruction.
762 // FIXME-PERF: If it matters, we could let the target do this. It can
763 // probably do so more efficiently in many cases.
764 SmallVector<MCFixup, 4> Fixups;
765 SmallString<256> Code;
766 raw_svector_ostream VecOS(Code);
767 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
770 // Update the instruction fragment.
771 int SlideAmount = Code.size() - IF->getInstSize();
772 IF->setInst(Relaxed);
773 IF->getCode() = Code;
774 IF->getFixups().clear();
775 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
776 MCFixup &F = Fixups[i];
777 IF->getFixups().push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
781 // Update the layout, and remember that we relaxed. If we are relaxing
782 // everything, we can skip this step since nothing will depend on updating
785 Layout.UpdateForSlide(IF, SlideAmount);
793 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
794 // Lower out any instruction fragments, to simplify the fixup application and
797 // FIXME-PERF: We don't have to do this, but the assumption is that it is
798 // cheap (we will mostly end up eliminating fragments and appending on to data
799 // fragments), so the extra complexity downstream isn't worth it. Evaluate
801 for (iterator it = begin(), ie = end(); it != ie; ++it) {
802 MCSectionData &SD = *it;
804 for (MCSectionData::iterator it2 = SD.begin(),
805 ie2 = SD.end(); it2 != ie2; ++it2) {
806 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
810 // Create a new data fragment for the instruction.
812 // FIXME-PERF: Reuse previous data fragment if possible.
813 MCDataFragment *DF = new MCDataFragment();
814 SD.getFragmentList().insert(it2, DF);
816 // Update the data fragments layout data.
818 // FIXME: Add MCAsmLayout utility for this.
819 DF->setParent(IF->getParent());
820 DF->setAtom(IF->getAtom());
821 DF->setOrdinal(IF->getOrdinal());
822 Layout.setFragmentOffset(DF, Layout.getFragmentOffset(IF));
823 Layout.setFragmentEffectiveSize(DF, Layout.getFragmentEffectiveSize(IF));
825 // Copy in the data and the fixups.
826 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
827 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
828 DF->getFixups().push_back(IF->getFixups()[i]);
830 // Delete the instruction fragment and update the iterator.
831 SD.getFragmentList().erase(IF);
841 raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
842 OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << *AF.Value
843 << " Kind:" << AF.Kind << ">";
849 void MCFragment::dump() {
850 raw_ostream &OS = llvm::errs();
852 OS << "<MCFragment " << (void*) this << " Offset:" << Offset
853 << " EffectiveSize:" << EffectiveSize;
858 void MCAlignFragment::dump() {
859 raw_ostream &OS = llvm::errs();
861 OS << "<MCAlignFragment ";
862 this->MCFragment::dump();
864 OS << " Alignment:" << getAlignment()
865 << " Value:" << getValue() << " ValueSize:" << getValueSize()
866 << " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
869 void MCDataFragment::dump() {
870 raw_ostream &OS = llvm::errs();
872 OS << "<MCDataFragment ";
873 this->MCFragment::dump();
876 for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
878 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
880 OS << "] (" << getContents().size() << " bytes)";
882 if (!getFixups().empty()) {
885 for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
886 if (it != fixup_begin()) OS << ",\n ";
895 void MCFillFragment::dump() {
896 raw_ostream &OS = llvm::errs();
898 OS << "<MCFillFragment ";
899 this->MCFragment::dump();
901 OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
902 << " Size:" << getSize() << ">";
905 void MCInstFragment::dump() {
906 raw_ostream &OS = llvm::errs();
908 OS << "<MCInstFragment ";
909 this->MCFragment::dump();
912 getInst().dump_pretty(OS);
916 void MCOrgFragment::dump() {
917 raw_ostream &OS = llvm::errs();
919 OS << "<MCOrgFragment ";
920 this->MCFragment::dump();
922 OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
925 void MCZeroFillFragment::dump() {
926 raw_ostream &OS = llvm::errs();
928 OS << "<MCZeroFillFragment ";
929 this->MCFragment::dump();
931 OS << " Size:" << getSize() << ">";
934 void MCSectionData::dump() {
935 raw_ostream &OS = llvm::errs();
937 OS << "<MCSectionData";
938 OS << " Alignment:" << getAlignment() << " Address:" << Address
939 << " Size:" << Size << " FileSize:" << FileSize
940 << " Fragments:[\n ";
941 for (iterator it = begin(), ie = end(); it != ie; ++it) {
942 if (it != begin()) OS << ",\n ";
948 void MCSymbolData::dump() {
949 raw_ostream &OS = llvm::errs();
951 OS << "<MCSymbolData Symbol:" << getSymbol()
952 << " Fragment:" << getFragment() << " Offset:" << getOffset()
953 << " Flags:" << getFlags() << " Index:" << getIndex();
955 OS << " (common, size:" << getCommonSize()
956 << " align: " << getCommonAlignment() << ")";
959 if (isPrivateExtern())
960 OS << " (private extern)";
964 void MCAssembler::dump() {
965 raw_ostream &OS = llvm::errs();
967 OS << "<MCAssembler\n";
968 OS << " Sections:[\n ";
969 for (iterator it = begin(), ie = end(); it != ie; ++it) {
970 if (it != begin()) OS << ",\n ";
976 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
977 if (it != symbol_begin()) OS << ",\n ";