MCDwarf: Invert the Section+CU->LineEntries mapping so the CU is the primary dimension

This makes the mapping consistent with other CU->X mappings in the
MCContext, helping pave the way to refactor all these values into a
single data structure per CU and thus a single map.

I haven't renamed the data structure as that would make the patch churn
even higher (the MCLineSection name no longer makes sense, as this
structure now contains lines for multiple sections covered by a single
CU, rather than lines for a single section in multiple CUs) and further
refactorings will follow that may remove this type entirely.

For convenience, I also gave the MCLineSection value semantics so we
didn't have to do the lazy construction, manual delete, etc.

(& for those playing at home, refactoring the line printing into a
single data structure will eventually alow that data structure to be
reused to own the debug_line.dwo line table used for type unit file name
resolution)

llvm-svn: 203726

2 files changed, 14 insertions, 46 deletions

diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 5c515b4f1eb..718c3cefaa3 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -89,7 +89,6 @@ void MCContext::reset() {
   MCGenDwarfLabelEntries.clear();
   DwarfDebugFlags = StringRef();
   MCLineSections.clear();
-  MCLineSectionOrder.clear();
   DwarfCompileUnitID = 0;
   MCLineTableSymbols.clear();
   CurrentDwarfLoc = MCDwarfLoc(0,0,0,DWARF2_FLAG_IS_STMT,0,0);
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 98d78737cc6..ba61a5d8ce3 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -80,23 +80,10 @@ void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
   // clear DwarfLocSeen saying the current .loc info is now used.
   MCOS->getContext().ClearDwarfLocSeen();
 
-  // Get the MCLineSection for this section, if one does not exist for this
-  // section create it.
-  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
-    MCOS->getContext().getMCLineSections();
-  MCLineSection *LineSection = MCLineSections.lookup(Section);
-  if (!LineSection) {
-    // Create a new MCLineSection.  This will be deleted after the dwarf line
-    // table is created using it by iterating through the MCLineSections
-    // DenseMap.
-    LineSection = new MCLineSection;
-    // Save a pointer to the new LineSection into the MCLineSections DenseMap.
-    MCOS->getContext().addMCLineSection(Section, LineSection);
-  }
-
   // Add the line entry to this section's entries.
-  LineSection->addLineEntry(LineEntry,
-                            MCOS->getContext().getDwarfCompileUnitID());
+  MCOS->getContext()
+      .getMCLineSections()[MCOS->getContext().getDwarfCompileUnitID()]
+      .addLineEntry(LineEntry, Section);
 }
 
 //
@@ -126,12 +113,8 @@ static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
 //
 static inline void EmitDwarfLineTable(MCStreamer *MCOS,
                                       const MCSection *Section,
-                                      const MCLineSection *LineSection,
+                                      const MCLineSection::MCLineEntryCollection &LineEntries,
                                       unsigned CUID) {
-  // This LineSection does not contain any LineEntry for the given Compile Unit.
-  if (!LineSection->containEntriesForID(CUID))
-    return;
-
   unsigned FileNum = 1;
   unsigned LastLine = 1;
   unsigned Column = 0;
@@ -141,9 +124,9 @@ static inline void EmitDwarfLineTable(MCStreamer *MCOS,
   MCSymbol *LastLabel = NULL;
 
   // Loop through each MCLineEntry and encode the dwarf line number table.
-  for (MCLineSection::const_iterator
-         it = LineSection->getMCLineEntries(CUID).begin(),
-         ie = LineSection->getMCLineEntries(CUID).end(); it != ie; ++it) {
+  for (auto it = LineEntries.begin(),
+            ie = LineEntries.end();
+       it != ie; ++it) {
 
     if (FileNum != it->getFileNum()) {
       FileNum = it->getFileNum();
@@ -236,15 +219,6 @@ const MCSymbol *MCDwarfFileTable::Emit(MCStreamer *MCOS) {
   for (unsigned Is = 1, Ie = MCLineTableSymbols.size(); Is < Ie; Is++)
     EmitCU(MCOS, Is);
 
-  // Now delete the MCLineSections that were created in MCLineEntry::Make()
-  // and used to emit the line table.
-  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
-    MCOS->getContext().getMCLineSections();
-  for (DenseMap<const MCSection *, MCLineSection *>::const_iterator it =
-       MCLineSections.begin(), ie = MCLineSections.end(); it != ie;
-       ++it)
-    delete it->second;
-
   return LineStartSym;
 }
 
@@ -329,20 +303,15 @@ const MCSymbol *MCDwarfFileTable::EmitCU(MCStreamer *MCOS, unsigned CUID) {
   MCOS->EmitLabel(ProEndSym);
 
   // Put out the line tables.
-  const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
+  const std::map<unsigned, MCLineSection> &MCLineSections =
     MCOS->getContext().getMCLineSections();
-  const std::vector<const MCSection *> &MCLineSectionOrder =
-    MCOS->getContext().getMCLineSectionOrder();
-  for (std::vector<const MCSection*>::const_iterator it =
-         MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
-       ++it) {
-    const MCSection *Sec = *it;
-    const MCLineSection *Line = MCLineSections.lookup(Sec);
-    EmitDwarfLineTable(MCOS, Sec, Line, CUID);
-  }
+  auto Iter = MCLineSections.find(CUID);
+  if (Iter != MCLineSections.end())
+    for (const auto &LineSec : Iter->second.getMCLineEntries())
+      EmitDwarfLineTable(MCOS, LineSec.first, LineSec.second, CUID);
 
-  if (MCOS->getContext().getAsmInfo()->getLinkerRequiresNonEmptyDwarfLines()
-      && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
+  if (MCOS->getContext().getAsmInfo()->getLinkerRequiresNonEmptyDwarfLines() &&
+      Iter == MCLineSections.end()) {
     // The darwin9 linker has a bug (see PR8715). For for 32-bit architectures
     // it requires:
     // total_length >= prologue_length + 10