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Diffstat (limited to 'llvm/lib/MC/MCCodeView.cpp')
| -rw-r--r-- | llvm/lib/MC/MCCodeView.cpp | 696 |
1 files changed, 696 insertions, 0 deletions
diff --git a/llvm/lib/MC/MCCodeView.cpp b/llvm/lib/MC/MCCodeView.cpp new file mode 100644 index 000000000000..1a71b542bd06 --- /dev/null +++ b/llvm/lib/MC/MCCodeView.cpp @@ -0,0 +1,696 @@ +//===- MCCodeView.h - Machine Code CodeView support -------------*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// Holds state from .cv_file and .cv_loc directives for later emission. +// +//===----------------------------------------------------------------------===// + +#include "llvm/MC/MCCodeView.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/StringExtras.h" +#include "llvm/DebugInfo/CodeView/CodeView.h" +#include "llvm/DebugInfo/CodeView/Line.h" +#include "llvm/DebugInfo/CodeView/SymbolRecord.h" +#include "llvm/MC/MCAsmLayout.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCObjectStreamer.h" +#include "llvm/MC/MCValue.h" +#include "llvm/Support/EndianStream.h" + +using namespace llvm; +using namespace llvm::codeview; + +CodeViewContext::CodeViewContext() {} + +CodeViewContext::~CodeViewContext() { + // If someone inserted strings into the string table but never actually + // emitted them somewhere, clean up the fragment. + if (!InsertedStrTabFragment) + delete StrTabFragment; +} + +/// This is a valid number for use with .cv_loc if we've already seen a .cv_file +/// for it. +bool CodeViewContext::isValidFileNumber(unsigned FileNumber) const { + unsigned Idx = FileNumber - 1; + if (Idx < Files.size()) + return Files[Idx].Assigned; + return false; +} + +bool CodeViewContext::addFile(MCStreamer &OS, unsigned FileNumber, + StringRef Filename, + ArrayRef<uint8_t> ChecksumBytes, + uint8_t ChecksumKind) { + assert(FileNumber > 0); + auto FilenameOffset = addToStringTable(Filename); + Filename = FilenameOffset.first; + unsigned Idx = FileNumber - 1; + if (Idx >= Files.size()) + Files.resize(Idx + 1); + + if (Filename.empty()) + Filename = "<stdin>"; + + if (Files[Idx].Assigned) + return false; + + FilenameOffset = addToStringTable(Filename); + Filename = FilenameOffset.first; + unsigned Offset = FilenameOffset.second; + + auto ChecksumOffsetSymbol = + OS.getContext().createTempSymbol("checksum_offset", false); + Files[Idx].StringTableOffset = Offset; + Files[Idx].ChecksumTableOffset = ChecksumOffsetSymbol; + Files[Idx].Assigned = true; + Files[Idx].Checksum = ChecksumBytes; + Files[Idx].ChecksumKind = ChecksumKind; + + return true; +} + +MCCVFunctionInfo *CodeViewContext::getCVFunctionInfo(unsigned FuncId) { + if (FuncId >= Functions.size()) + return nullptr; + if (Functions[FuncId].isUnallocatedFunctionInfo()) + return nullptr; + return &Functions[FuncId]; +} + +bool CodeViewContext::recordFunctionId(unsigned FuncId) { + if (FuncId >= Functions.size()) + Functions.resize(FuncId + 1); + + // Return false if this function info was already allocated. + if (!Functions[FuncId].isUnallocatedFunctionInfo()) + return false; + + // Mark this as an allocated normal function, and leave the rest alone. + Functions[FuncId].ParentFuncIdPlusOne = MCCVFunctionInfo::FunctionSentinel; + return true; +} + +bool CodeViewContext::recordInlinedCallSiteId(unsigned FuncId, unsigned IAFunc, + unsigned IAFile, unsigned IALine, + unsigned IACol) { + if (FuncId >= Functions.size()) + Functions.resize(FuncId + 1); + + // Return false if this function info was already allocated. + if (!Functions[FuncId].isUnallocatedFunctionInfo()) + return false; + + MCCVFunctionInfo::LineInfo InlinedAt; + InlinedAt.File = IAFile; + InlinedAt.Line = IALine; + InlinedAt.Col = IACol; + + // Mark this as an inlined call site and record call site line info. + MCCVFunctionInfo *Info = &Functions[FuncId]; + Info->ParentFuncIdPlusOne = IAFunc + 1; + Info->InlinedAt = InlinedAt; + + // Walk up the call chain adding this function id to the InlinedAtMap of all + // transitive callers until we hit a real function. + while (Info->isInlinedCallSite()) { + InlinedAt = Info->InlinedAt; + Info = getCVFunctionInfo(Info->getParentFuncId()); + Info->InlinedAtMap[FuncId] = InlinedAt; + } + + return true; +} + +void CodeViewContext::recordCVLoc(MCContext &Ctx, const MCSymbol *Label, + unsigned FunctionId, unsigned FileNo, + unsigned Line, unsigned Column, + bool PrologueEnd, bool IsStmt) { + addLineEntry(MCCVLoc{ + Label, FunctionId, FileNo, Line, Column, PrologueEnd, IsStmt}); +} + +MCDataFragment *CodeViewContext::getStringTableFragment() { + if (!StrTabFragment) { + StrTabFragment = new MCDataFragment(); + // Start a new string table out with a null byte. + StrTabFragment->getContents().push_back('\0'); + } + return StrTabFragment; +} + +std::pair<StringRef, unsigned> CodeViewContext::addToStringTable(StringRef S) { + SmallVectorImpl<char> &Contents = getStringTableFragment()->getContents(); + auto Insertion = + StringTable.insert(std::make_pair(S, unsigned(Contents.size()))); + // Return the string from the table, since it is stable. + std::pair<StringRef, unsigned> Ret = + std::make_pair(Insertion.first->first(), Insertion.first->second); + if (Insertion.second) { + // The string map key is always null terminated. + Contents.append(Ret.first.begin(), Ret.first.end() + 1); + } + return Ret; +} + +unsigned CodeViewContext::getStringTableOffset(StringRef S) { + // A string table offset of zero is always the empty string. + if (S.empty()) + return 0; + auto I = StringTable.find(S); + assert(I != StringTable.end()); + return I->second; +} + +void CodeViewContext::emitStringTable(MCObjectStreamer &OS) { + MCContext &Ctx = OS.getContext(); + MCSymbol *StringBegin = Ctx.createTempSymbol("strtab_begin", false), + *StringEnd = Ctx.createTempSymbol("strtab_end", false); + + OS.EmitIntValue(unsigned(DebugSubsectionKind::StringTable), 4); + OS.emitAbsoluteSymbolDiff(StringEnd, StringBegin, 4); + OS.EmitLabel(StringBegin); + + // Put the string table data fragment here, if we haven't already put it + // somewhere else. If somebody wants two string tables in their .s file, one + // will just be empty. + if (!InsertedStrTabFragment) { + OS.insert(getStringTableFragment()); + InsertedStrTabFragment = true; + } + + OS.EmitValueToAlignment(4, 0); + + OS.EmitLabel(StringEnd); +} + +void CodeViewContext::emitFileChecksums(MCObjectStreamer &OS) { + // Do nothing if there are no file checksums. Microsoft's linker rejects empty + // CodeView substreams. + if (Files.empty()) + return; + + MCContext &Ctx = OS.getContext(); + MCSymbol *FileBegin = Ctx.createTempSymbol("filechecksums_begin", false), + *FileEnd = Ctx.createTempSymbol("filechecksums_end", false); + + OS.EmitIntValue(unsigned(DebugSubsectionKind::FileChecksums), 4); + OS.emitAbsoluteSymbolDiff(FileEnd, FileBegin, 4); + OS.EmitLabel(FileBegin); + + unsigned CurrentOffset = 0; + + // Emit an array of FileChecksum entries. We index into this table using the + // user-provided file number. Each entry may be a variable number of bytes + // determined by the checksum kind and size. + for (auto File : Files) { + OS.EmitAssignment(File.ChecksumTableOffset, + MCConstantExpr::create(CurrentOffset, Ctx)); + CurrentOffset += 4; // String table offset. + if (!File.ChecksumKind) { + CurrentOffset += + 4; // One byte each for checksum size and kind, then align to 4 bytes. + } else { + CurrentOffset += 2; // One byte each for checksum size and kind. + CurrentOffset += File.Checksum.size(); + CurrentOffset = alignTo(CurrentOffset, 4); + } + + OS.EmitIntValue(File.StringTableOffset, 4); + + if (!File.ChecksumKind) { + // There is no checksum. Therefore zero the next two fields and align + // back to 4 bytes. + OS.EmitIntValue(0, 4); + continue; + } + OS.EmitIntValue(static_cast<uint8_t>(File.Checksum.size()), 1); + OS.EmitIntValue(File.ChecksumKind, 1); + OS.EmitBytes(toStringRef(File.Checksum)); + OS.EmitValueToAlignment(4); + } + + OS.EmitLabel(FileEnd); + + ChecksumOffsetsAssigned = true; +} + +// Output checksum table offset of the given file number. It is possible that +// not all files have been registered yet, and so the offset cannot be +// calculated. In this case a symbol representing the offset is emitted, and +// the value of this symbol will be fixed up at a later time. +void CodeViewContext::emitFileChecksumOffset(MCObjectStreamer &OS, + unsigned FileNo) { + unsigned Idx = FileNo - 1; + + if (Idx >= Files.size()) + Files.resize(Idx + 1); + + if (ChecksumOffsetsAssigned) { + OS.EmitSymbolValue(Files[Idx].ChecksumTableOffset, 4); + return; + } + + const MCSymbolRefExpr *SRE = + MCSymbolRefExpr::create(Files[Idx].ChecksumTableOffset, OS.getContext()); + + OS.EmitValueImpl(SRE, 4); +} + +void CodeViewContext::addLineEntry(const MCCVLoc &LineEntry) { + size_t Offset = MCCVLines.size(); + auto I = MCCVLineStartStop.insert( + {LineEntry.getFunctionId(), {Offset, Offset + 1}}); + if (!I.second) + I.first->second.second = Offset + 1; + MCCVLines.push_back(LineEntry); +} + +std::vector<MCCVLoc> +CodeViewContext::getFunctionLineEntries(unsigned FuncId) { + std::vector<MCCVLoc> FilteredLines; + auto I = MCCVLineStartStop.find(FuncId); + if (I != MCCVLineStartStop.end()) { + MCCVFunctionInfo *SiteInfo = getCVFunctionInfo(FuncId); + for (size_t Idx = I->second.first, End = I->second.second; Idx != End; + ++Idx) { + unsigned LocationFuncId = MCCVLines[Idx].getFunctionId(); + if (LocationFuncId == FuncId) { + // This was a .cv_loc directly for FuncId, so record it. + FilteredLines.push_back(MCCVLines[Idx]); + } else { + // Check if the current location is inlined in this function. If it is, + // synthesize a statement .cv_loc at the original inlined call site. + auto I = SiteInfo->InlinedAtMap.find(LocationFuncId); + if (I != SiteInfo->InlinedAtMap.end()) { + MCCVFunctionInfo::LineInfo &IA = I->second; + // Only add the location if it differs from the previous location. + // Large inlined calls will have many .cv_loc entries and we only need + // one line table entry in the parent function. + if (FilteredLines.empty() || + FilteredLines.back().getFileNum() != IA.File || + FilteredLines.back().getLine() != IA.Line || + FilteredLines.back().getColumn() != IA.Col) { + FilteredLines.push_back(MCCVLoc( + MCCVLines[Idx].getLabel(), + FuncId, IA.File, IA.Line, IA.Col, false, false)); + } + } + } + } + } + return FilteredLines; +} + +std::pair<size_t, size_t> CodeViewContext::getLineExtent(unsigned FuncId) { + auto I = MCCVLineStartStop.find(FuncId); + // Return an empty extent if there are no cv_locs for this function id. + if (I == MCCVLineStartStop.end()) + return {~0ULL, 0}; + return I->second; +} + +ArrayRef<MCCVLoc> CodeViewContext::getLinesForExtent(size_t L, size_t R) { + if (R <= L) + return None; + if (L >= MCCVLines.size()) + return None; + return makeArrayRef(&MCCVLines[L], R - L); +} + +void CodeViewContext::emitLineTableForFunction(MCObjectStreamer &OS, + unsigned FuncId, + const MCSymbol *FuncBegin, + const MCSymbol *FuncEnd) { + MCContext &Ctx = OS.getContext(); + MCSymbol *LineBegin = Ctx.createTempSymbol("linetable_begin", false), + *LineEnd = Ctx.createTempSymbol("linetable_end", false); + + OS.EmitIntValue(unsigned(DebugSubsectionKind::Lines), 4); + OS.emitAbsoluteSymbolDiff(LineEnd, LineBegin, 4); + OS.EmitLabel(LineBegin); + OS.EmitCOFFSecRel32(FuncBegin, /*Offset=*/0); + OS.EmitCOFFSectionIndex(FuncBegin); + + // Actual line info. + std::vector<MCCVLoc> Locs = getFunctionLineEntries(FuncId); + bool HaveColumns = any_of(Locs, [](const MCCVLoc &LineEntry) { + return LineEntry.getColumn() != 0; + }); + OS.EmitIntValue(HaveColumns ? int(LF_HaveColumns) : 0, 2); + OS.emitAbsoluteSymbolDiff(FuncEnd, FuncBegin, 4); + + for (auto I = Locs.begin(), E = Locs.end(); I != E;) { + // Emit a file segment for the run of locations that share a file id. + unsigned CurFileNum = I->getFileNum(); + auto FileSegEnd = + std::find_if(I, E, [CurFileNum](const MCCVLoc &Loc) { + return Loc.getFileNum() != CurFileNum; + }); + unsigned EntryCount = FileSegEnd - I; + OS.AddComment( + "Segment for file '" + + Twine(getStringTableFragment() + ->getContents()[Files[CurFileNum - 1].StringTableOffset]) + + "' begins"); + OS.EmitCVFileChecksumOffsetDirective(CurFileNum); + OS.EmitIntValue(EntryCount, 4); + uint32_t SegmentSize = 12; + SegmentSize += 8 * EntryCount; + if (HaveColumns) + SegmentSize += 4 * EntryCount; + OS.EmitIntValue(SegmentSize, 4); + + for (auto J = I; J != FileSegEnd; ++J) { + OS.emitAbsoluteSymbolDiff(J->getLabel(), FuncBegin, 4); + unsigned LineData = J->getLine(); + if (J->isStmt()) + LineData |= LineInfo::StatementFlag; + OS.EmitIntValue(LineData, 4); + } + if (HaveColumns) { + for (auto J = I; J != FileSegEnd; ++J) { + OS.EmitIntValue(J->getColumn(), 2); + OS.EmitIntValue(0, 2); + } + } + I = FileSegEnd; + } + OS.EmitLabel(LineEnd); +} + +static bool compressAnnotation(uint32_t Data, SmallVectorImpl<char> &Buffer) { + if (isUInt<7>(Data)) { + Buffer.push_back(Data); + return true; + } + + if (isUInt<14>(Data)) { + Buffer.push_back((Data >> 8) | 0x80); + Buffer.push_back(Data & 0xff); + return true; + } + + if (isUInt<29>(Data)) { + Buffer.push_back((Data >> 24) | 0xC0); + Buffer.push_back((Data >> 16) & 0xff); + Buffer.push_back((Data >> 8) & 0xff); + Buffer.push_back(Data & 0xff); + return true; + } + + return false; +} + +static bool compressAnnotation(BinaryAnnotationsOpCode Annotation, + SmallVectorImpl<char> &Buffer) { + return compressAnnotation(static_cast<uint32_t>(Annotation), Buffer); +} + +static uint32_t encodeSignedNumber(uint32_t Data) { + if (Data >> 31) + return ((-Data) << 1) | 1; + return Data << 1; +} + +void CodeViewContext::emitInlineLineTableForFunction(MCObjectStreamer &OS, + unsigned PrimaryFunctionId, + unsigned SourceFileId, + unsigned SourceLineNum, + const MCSymbol *FnStartSym, + const MCSymbol *FnEndSym) { + // Create and insert a fragment into the current section that will be encoded + // later. + new MCCVInlineLineTableFragment(PrimaryFunctionId, SourceFileId, + SourceLineNum, FnStartSym, FnEndSym, + OS.getCurrentSectionOnly()); +} + +MCFragment *CodeViewContext::emitDefRange( + MCObjectStreamer &OS, + ArrayRef<std::pair<const MCSymbol *, const MCSymbol *>> Ranges, + StringRef FixedSizePortion) { + // Create and insert a fragment into the current section that will be encoded + // later. + return new MCCVDefRangeFragment(Ranges, FixedSizePortion, + OS.getCurrentSectionOnly()); +} + +static unsigned computeLabelDiff(MCAsmLayout &Layout, const MCSymbol *Begin, + const MCSymbol *End) { + MCContext &Ctx = Layout.getAssembler().getContext(); + MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None; + const MCExpr *BeginRef = MCSymbolRefExpr::create(Begin, Variant, Ctx), + *EndRef = MCSymbolRefExpr::create(End, Variant, Ctx); + const MCExpr *AddrDelta = + MCBinaryExpr::create(MCBinaryExpr::Sub, EndRef, BeginRef, Ctx); + int64_t Result; + bool Success = AddrDelta->evaluateKnownAbsolute(Result, Layout); + assert(Success && "failed to evaluate label difference as absolute"); + (void)Success; + assert(Result >= 0 && "negative label difference requested"); + assert(Result < UINT_MAX && "label difference greater than 2GB"); + return unsigned(Result); +} + +void CodeViewContext::encodeInlineLineTable(MCAsmLayout &Layout, + MCCVInlineLineTableFragment &Frag) { + size_t LocBegin; + size_t LocEnd; + std::tie(LocBegin, LocEnd) = getLineExtent(Frag.SiteFuncId); + + // Include all child inline call sites in our .cv_loc extent. + MCCVFunctionInfo *SiteInfo = getCVFunctionInfo(Frag.SiteFuncId); + for (auto &KV : SiteInfo->InlinedAtMap) { + unsigned ChildId = KV.first; + auto Extent = getLineExtent(ChildId); + LocBegin = std::min(LocBegin, Extent.first); + LocEnd = std::max(LocEnd, Extent.second); + } + + if (LocBegin >= LocEnd) + return; + ArrayRef<MCCVLoc> Locs = getLinesForExtent(LocBegin, LocEnd); + if (Locs.empty()) + return; + + // Check that the locations are all in the same section. +#ifndef NDEBUG + const MCSection *FirstSec = &Locs.front().getLabel()->getSection(); + for (const MCCVLoc &Loc : Locs) { + if (&Loc.getLabel()->getSection() != FirstSec) { + errs() << ".cv_loc " << Loc.getFunctionId() << ' ' << Loc.getFileNum() + << ' ' << Loc.getLine() << ' ' << Loc.getColumn() + << " is in the wrong section\n"; + llvm_unreachable(".cv_loc crosses sections"); + } + } +#endif + + // Make an artificial start location using the function start and the inlinee + // lines start location information. All deltas start relative to this + // location. + MCCVLoc StartLoc = Locs.front(); + StartLoc.setLabel(Frag.getFnStartSym()); + StartLoc.setFileNum(Frag.StartFileId); + StartLoc.setLine(Frag.StartLineNum); + bool HaveOpenRange = false; + + const MCSymbol *LastLabel = Frag.getFnStartSym(); + MCCVFunctionInfo::LineInfo LastSourceLoc, CurSourceLoc; + LastSourceLoc.File = Frag.StartFileId; + LastSourceLoc.Line = Frag.StartLineNum; + + SmallVectorImpl<char> &Buffer = Frag.getContents(); + Buffer.clear(); // Clear old contents if we went through relaxation. + for (const MCCVLoc &Loc : Locs) { + // Exit early if our line table would produce an oversized InlineSiteSym + // record. Account for the ChangeCodeLength annotation emitted after the + // loop ends. + constexpr uint32_t InlineSiteSize = 12; + constexpr uint32_t AnnotationSize = 8; + size_t MaxBufferSize = MaxRecordLength - InlineSiteSize - AnnotationSize; + if (Buffer.size() >= MaxBufferSize) + break; + + if (Loc.getFunctionId() == Frag.SiteFuncId) { + CurSourceLoc.File = Loc.getFileNum(); + CurSourceLoc.Line = Loc.getLine(); + } else { + auto I = SiteInfo->InlinedAtMap.find(Loc.getFunctionId()); + if (I != SiteInfo->InlinedAtMap.end()) { + // This .cv_loc is from a child inline call site. Use the source + // location of the inlined call site instead of the .cv_loc directive + // source location. + CurSourceLoc = I->second; + } else { + // We've hit a cv_loc not attributed to this inline call site. Use this + // label to end the PC range. + if (HaveOpenRange) { + unsigned Length = computeLabelDiff(Layout, LastLabel, Loc.getLabel()); + compressAnnotation(BinaryAnnotationsOpCode::ChangeCodeLength, Buffer); + compressAnnotation(Length, Buffer); + LastLabel = Loc.getLabel(); + } + HaveOpenRange = false; + continue; + } + } + + // Skip this .cv_loc if we have an open range and this isn't a meaningful + // source location update. The current table format does not support column + // info, so we can skip updates for those. + if (HaveOpenRange && CurSourceLoc.File == LastSourceLoc.File && + CurSourceLoc.Line == LastSourceLoc.Line) + continue; + + HaveOpenRange = true; + + if (CurSourceLoc.File != LastSourceLoc.File) { + unsigned FileOffset = static_cast<const MCConstantExpr *>( + Files[CurSourceLoc.File - 1] + .ChecksumTableOffset->getVariableValue()) + ->getValue(); + compressAnnotation(BinaryAnnotationsOpCode::ChangeFile, Buffer); + compressAnnotation(FileOffset, Buffer); + } + + int LineDelta = CurSourceLoc.Line - LastSourceLoc.Line; + unsigned EncodedLineDelta = encodeSignedNumber(LineDelta); + unsigned CodeDelta = computeLabelDiff(Layout, LastLabel, Loc.getLabel()); + if (CodeDelta == 0 && LineDelta != 0) { + compressAnnotation(BinaryAnnotationsOpCode::ChangeLineOffset, Buffer); + compressAnnotation(EncodedLineDelta, Buffer); + } else if (EncodedLineDelta < 0x8 && CodeDelta <= 0xf) { + // The ChangeCodeOffsetAndLineOffset combination opcode is used when the + // encoded line delta uses 3 or fewer set bits and the code offset fits + // in one nibble. + unsigned Operand = (EncodedLineDelta << 4) | CodeDelta; + compressAnnotation(BinaryAnnotationsOpCode::ChangeCodeOffsetAndLineOffset, + Buffer); + compressAnnotation(Operand, Buffer); + } else { + // Otherwise use the separate line and code deltas. + if (LineDelta != 0) { + compressAnnotation(BinaryAnnotationsOpCode::ChangeLineOffset, Buffer); + compressAnnotation(EncodedLineDelta, Buffer); + } + compressAnnotation(BinaryAnnotationsOpCode::ChangeCodeOffset, Buffer); + compressAnnotation(CodeDelta, Buffer); + } + + LastLabel = Loc.getLabel(); + LastSourceLoc = CurSourceLoc; + } + + assert(HaveOpenRange); + + unsigned EndSymLength = + computeLabelDiff(Layout, LastLabel, Frag.getFnEndSym()); + unsigned LocAfterLength = ~0U; + ArrayRef<MCCVLoc> LocAfter = getLinesForExtent(LocEnd, LocEnd + 1); + if (!LocAfter.empty()) { + // Only try to compute this difference if we're in the same section. + const MCCVLoc &Loc = LocAfter[0]; + if (&Loc.getLabel()->getSection() == &LastLabel->getSection()) + LocAfterLength = computeLabelDiff(Layout, LastLabel, Loc.getLabel()); + } + + compressAnnotation(BinaryAnnotationsOpCode::ChangeCodeLength, Buffer); + compressAnnotation(std::min(EndSymLength, LocAfterLength), Buffer); +} + +void CodeViewContext::encodeDefRange(MCAsmLayout &Layout, + MCCVDefRangeFragment &Frag) { + MCContext &Ctx = Layout.getAssembler().getContext(); + SmallVectorImpl<char> &Contents = Frag.getContents(); + Contents.clear(); + SmallVectorImpl<MCFixup> &Fixups = Frag.getFixups(); + Fixups.clear(); + raw_svector_ostream OS(Contents); + + // Compute all the sizes up front. + SmallVector<std::pair<unsigned, unsigned>, 4> GapAndRangeSizes; + const MCSymbol *LastLabel = nullptr; + for (std::pair<const MCSymbol *, const MCSymbol *> Range : Frag.getRanges()) { + unsigned GapSize = + LastLabel ? computeLabelDiff(Layout, LastLabel, Range.first) : 0; + unsigned RangeSize = computeLabelDiff(Layout, Range.first, Range.second); + GapAndRangeSizes.push_back({GapSize, RangeSize}); + LastLabel = Range.second; + } + + // Write down each range where the variable is defined. + for (size_t I = 0, E = Frag.getRanges().size(); I != E;) { + // If the range size of multiple consecutive ranges is under the max, + // combine the ranges and emit some gaps. + const MCSymbol *RangeBegin = Frag.getRanges()[I].first; + unsigned RangeSize = GapAndRangeSizes[I].second; + size_t J = I + 1; + for (; J != E; ++J) { + unsigned GapAndRangeSize = GapAndRangeSizes[J].first + GapAndRangeSizes[J].second; + if (RangeSize + GapAndRangeSize > MaxDefRange) + break; + RangeSize += GapAndRangeSize; + } + unsigned NumGaps = J - I - 1; + + support::endian::Writer LEWriter(OS, support::little); + + unsigned Bias = 0; + // We must split the range into chunks of MaxDefRange, this is a fundamental + // limitation of the file format. + do { + uint16_t Chunk = std::min((uint32_t)MaxDefRange, RangeSize); + + const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(RangeBegin, Ctx); + const MCBinaryExpr *BE = + MCBinaryExpr::createAdd(SRE, MCConstantExpr::create(Bias, Ctx), Ctx); + MCValue Res; + BE->evaluateAsRelocatable(Res, &Layout, /*Fixup=*/nullptr); + + // Each record begins with a 2-byte number indicating how large the record + // is. + StringRef FixedSizePortion = Frag.getFixedSizePortion(); + // Our record is a fixed sized prefix and a LocalVariableAddrRange that we + // are artificially constructing. + size_t RecordSize = FixedSizePortion.size() + + sizeof(LocalVariableAddrRange) + 4 * NumGaps; + // Write out the record size. + LEWriter.write<uint16_t>(RecordSize); + // Write out the fixed size prefix. + OS << FixedSizePortion; + // Make space for a fixup that will eventually have a section relative + // relocation pointing at the offset where the variable becomes live. + Fixups.push_back(MCFixup::create(Contents.size(), BE, FK_SecRel_4)); + LEWriter.write<uint32_t>(0); // Fixup for code start. + // Make space for a fixup that will record the section index for the code. + Fixups.push_back(MCFixup::create(Contents.size(), BE, FK_SecRel_2)); + LEWriter.write<uint16_t>(0); // Fixup for section index. + // Write down the range's extent. + LEWriter.write<uint16_t>(Chunk); + + // Move on to the next range. + Bias += Chunk; + RangeSize -= Chunk; + } while (RangeSize > 0); + + // Emit the gaps afterwards. + assert((NumGaps == 0 || Bias <= MaxDefRange) && + "large ranges should not have gaps"); + unsigned GapStartOffset = GapAndRangeSizes[I].second; + for (++I; I != J; ++I) { + unsigned GapSize, RangeSize; + assert(I < GapAndRangeSizes.size()); + std::tie(GapSize, RangeSize) = GapAndRangeSizes[I]; + LEWriter.write<uint16_t>(GapStartOffset); + LEWriter.write<uint16_t>(GapSize); + GapStartOffset += GapSize + RangeSize; + } + } +} |