Re-land "[DebugInfo] Move function from line table to the prologue (NFC)"

In LLDB, when parsing type units, we don't need to parse the whole line
table. Instead, we only need to parse the "support files" from the line
table prologue.

To make that possible, this patch moves the respective functions from
the LineTable into the Prologue. Because I don't think users of the
LineTable should have to know that these files come from the Prologue,

I've left the original methods in place, and made them redirect to the
LineTable.

Differential revision: https://reviews.llvm.org/D64774

llvm-svn: 366164

Author: JDevlieghere

lld/ELF/InputFiles.cpp

@@ -320,7 +320,7 @@ ObjFile<ELFT>::getVariableLoc(StringRef name) {
   // Take file name string from line table.
   std::string fileName;
   if (!it->second.lt->getFileNameByIndex(
-          it->second.file, nullptr,
+          it->second.file, {},
           DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, fileName))
     return None;
 

llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h

@@ -121,6 +121,17 @@ class DWARFDebugLine {
       return LineBase + (int8_t)LineRange - 1;
     }
 
+    /// Get DWARF-version aware access to the file name entry at the provided
+    /// index.
+    const llvm::DWARFDebugLine::FileNameEntry &
+    getFileNameEntry(uint64_t Index) const;
+
+    bool hasFileAtIndex(uint64_t FileIndex) const;
+
+    bool getFileNameByIndex(uint64_t FileIndex, StringRef CompDir,
+                            DILineInfoSpecifier::FileLineInfoKind Kind,
+                            std::string &Result) const;
+
     void clear();
     void dump(raw_ostream &OS, DIDumpOptions DumpOptions) const;
     Error parse(const DWARFDataExtractor &DebugLineData, uint32_t *OffsetPtr,
@@ -240,16 +251,20 @@ class DWARFDebugLine {
     bool lookupAddressRange(object::SectionedAddress Address, uint64_t Size,
                             std::vector<uint32_t> &Result) const;
 
-    bool hasFileAtIndex(uint64_t FileIndex) const;
+    bool hasFileAtIndex(uint64_t FileIndex) const {
+      return Prologue.hasFileAtIndex(FileIndex);
+    }
 
     /// Extracts filename by its index in filename table in prologue.
     /// In Dwarf 4, the files are 1-indexed and the current compilation file
     /// name is not represented in the list. In DWARF v5, the files are
     /// 0-indexed and the primary source file has the index 0.
     /// Returns true on success.
-    bool getFileNameByIndex(uint64_t FileIndex, const char *CompDir,
+    bool getFileNameByIndex(uint64_t FileIndex, StringRef CompDir,
                             DILineInfoSpecifier::FileLineInfoKind Kind,
-                            std::string &Result) const;
+                            std::string &Result) const {
+      return Prologue.getFileNameByIndex(FileIndex, CompDir, Kind, Result);
+    }
 
     /// Fills the Result argument with the file and line information
     /// corresponding to Address. Returns true on success.
@@ -268,11 +283,6 @@ class DWARFDebugLine {
         std::function<void(Error)> RecoverableErrorCallback,
         raw_ostream *OS = nullptr);
 
-    /// Get DWARF-version aware access to the file name entry at the provided
-    /// index.
-    const llvm::DWARFDebugLine::FileNameEntry &
-        getFileNameEntry(uint64_t Index) const;
-
     using RowVector = std::vector<Row>;
     using RowIter = RowVector::const_iterator;
     using SequenceVector = std::vector<Sequence>;

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

@@ -66,6 +66,26 @@ void DWARFDebugLine::ContentTypeTracker::trackContentType(
 
 DWARFDebugLine::Prologue::Prologue() { clear(); }
 
+bool DWARFDebugLine::Prologue::hasFileAtIndex(uint64_t FileIndex) const {
+  uint16_t DwarfVersion = getVersion();
+  assert(DwarfVersion != 0 &&
+         "line table prologue has no dwarf version information");
+  if (DwarfVersion >= 5)
+    return FileIndex < FileNames.size();
+  return FileIndex != 0 && FileIndex <= FileNames.size();
+}
+
+const llvm::DWARFDebugLine::FileNameEntry &
+DWARFDebugLine::Prologue::getFileNameEntry(uint64_t Index) const {
+  uint16_t DwarfVersion = getVersion();
+  assert(DwarfVersion != 0 &&
+         "line table prologue has no dwarf version information");
+  // In DWARF v5 the file names are 0-indexed.
+  if (DwarfVersion >= 5)
+    return FileNames[Index];
+  return FileNames[Index - 1];
+}
+
 void DWARFDebugLine::Prologue::clear() {
   TotalLength = PrologueLength = 0;
   SegSelectorSize = 0;
@@ -968,30 +988,11 @@ bool DWARFDebugLine::LineTable::lookupAddressRangeImpl(
   return true;
 }
 
-bool DWARFDebugLine::LineTable::hasFileAtIndex(uint64_t FileIndex) const {
-  uint16_t DwarfVersion = Prologue.getVersion();
-  assert(DwarfVersion != 0 && "LineTable has no dwarf version information");
-  if (DwarfVersion >= 5)
-    return FileIndex < Prologue.FileNames.size();
-  return FileIndex != 0 && FileIndex <= Prologue.FileNames.size();
-}
-
-const llvm::DWARFDebugLine::FileNameEntry &
-DWARFDebugLine::LineTable::getFileNameEntry(uint64_t Index) const {
-  uint16_t DwarfVersion = Prologue.getVersion();
-  assert(DwarfVersion != 0 && "LineTable has no dwarf version information");
-  // In DWARF v5 the file names are 0-indexed.
-  if (DwarfVersion >= 5)
-    return Prologue.FileNames[Index];
-  else
-    return Prologue.FileNames[Index - 1];
-}
-
 Optional<StringRef> DWARFDebugLine::LineTable::getSourceByIndex(uint64_t FileIndex,
                                                                 FileLineInfoKind Kind) const {
-  if (Kind == FileLineInfoKind::None || !hasFileAtIndex(FileIndex))
+  if (Kind == FileLineInfoKind::None || !Prologue.hasFileAtIndex(FileIndex))
     return None;
-  const FileNameEntry &Entry = getFileNameEntry(FileIndex);
+  const FileNameEntry &Entry = Prologue.getFileNameEntry(FileIndex);
   if (Optional<const char *> source = Entry.Source.getAsCString())
     return StringRef(*source);
   return None;
@@ -1005,10 +1006,10 @@ static bool isPathAbsoluteOnWindowsOrPosix(const Twine &Path) {
          sys::path::is_absolute(Path, sys::path::Style::windows);
 }
 
-bool DWARFDebugLine::LineTable::getFileNameByIndex(uint64_t FileIndex,
-                                                   const char *CompDir,
-                                                   FileLineInfoKind Kind,
-                                                   std::string &Result) const {
+bool DWARFDebugLine::Prologue::getFileNameByIndex(uint64_t FileIndex,
+                                                  StringRef CompDir,
+                                                  FileLineInfoKind Kind,
+                                                  std::string &Result) const {
   if (Kind == FileLineInfoKind::None || !hasFileAtIndex(FileIndex))
     return false;
   const FileNameEntry &Entry = getFileNameEntry(FileIndex);
@@ -1022,20 +1023,18 @@ bool DWARFDebugLine::LineTable::getFileNameByIndex(uint64_t FileIndex,
   SmallString<16> FilePath;
   StringRef IncludeDir;
   // Be defensive about the contents of Entry.
-  if (Prologue.getVersion() >= 5) {
-    if (Entry.DirIdx < Prologue.IncludeDirectories.size())
-      IncludeDir =
-          Prologue.IncludeDirectories[Entry.DirIdx].getAsCString().getValue();
+  if (getVersion() >= 5) {
+    if (Entry.DirIdx < IncludeDirectories.size())
+      IncludeDir = IncludeDirectories[Entry.DirIdx].getAsCString().getValue();
   } else {
-    if (0 < Entry.DirIdx && Entry.DirIdx <= Prologue.IncludeDirectories.size())
-      IncludeDir = Prologue.IncludeDirectories[Entry.DirIdx - 1]
-                       .getAsCString()
-                       .getValue();
+    if (0 < Entry.DirIdx && Entry.DirIdx <= IncludeDirectories.size())
+      IncludeDir =
+          IncludeDirectories[Entry.DirIdx - 1].getAsCString().getValue();
 
     // We may still need to append compilation directory of compile unit.
     // We know that FileName is not absolute, the only way to have an
     // absolute path at this point would be if IncludeDir is absolute.
-    if (CompDir && !isPathAbsoluteOnWindowsOrPosix(IncludeDir))
+    if (!CompDir.empty() && !isPathAbsoluteOnWindowsOrPosix(IncludeDir))
       sys::path::append(FilePath, CompDir);
   }