Dwarf: support for LTO where a single object file can have multiple line tables

We generate one line table for each compilation unit in the object file.
Reviewed by Eric and Kevin.

rdar://problem/13067005


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174445 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 41 insertions, 12 deletions

diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 3cf47bc6c5..5465af6385 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -101,7 +101,8 @@ void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
   }
 
   // Add the line entry to this section's entries.
-  LineSection->addLineEntry(LineEntry);
+  LineSection->addLineEntry(LineEntry,
+                            MCOS->getContext().getDwarfCompileUnitID());
 }
 
 //
@@ -131,7 +132,12 @@ static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
 //
 static inline void EmitDwarfLineTable(MCStreamer *MCOS,
                                       const MCSection *Section,
-                                      const MCLineSection *LineSection) {
+                                      const MCLineSection *LineSection,
+                                      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;
@@ -141,8 +147,8 @@ static inline void EmitDwarfLineTable(MCStreamer *MCOS,
 
   // Loop through each MCLineEntry and encode the dwarf line number table.
   for (MCLineSection::const_iterator
-         it = LineSection->getMCLineEntries()->begin(),
-         ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {
+         it = LineSection->getMCLineEntries(CUID).begin(),
+         ie = LineSection->getMCLineEntries(CUID).end(); it != ie; ++it) {
 
     if (FileNum != it->getFileNum()) {
       FileNum = it->getFileNum();
@@ -215,9 +221,36 @@ const MCSymbol *MCDwarfFileTable::Emit(MCStreamer *MCOS) {
   // Switch to the section where the table will be emitted into.
   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
 
-  // Create a symbol at the beginning of this section.
-  MCSymbol *LineStartSym = context.CreateTempSymbol();
-  // Set the value of the symbol, as we are at the start of the section.
+  const DenseMap<unsigned, MCSymbol *> &MCLineTableSymbols =
+    MCOS->getContext().getMCLineTableSymbols();
+  // CUID and MCLineTableSymbols are set in DwarfDebug, when DwarfDebug does
+  // not exist, CUID will be 0 and MCLineTableSymbols will be empty.
+  // Handle Compile Unit 0, the line table start symbol is the section symbol.
+  const MCSymbol *LineStartSym = EmitCU(MCOS, 0);
+  // Handle the rest of the Compile Units.
+  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;
+}
+
+const MCSymbol *MCDwarfFileTable::EmitCU(MCStreamer *MCOS, unsigned CUID) {
+  MCContext &context = MCOS->getContext();
+
+  // Create a symbol at the beginning of the line table.
+  MCSymbol *LineStartSym = MCOS->getContext().getMCLineTableSymbol(CUID);
+  if (!LineStartSym)
+    LineStartSym = context.CreateTempSymbol();
+  // Set the value of the symbol, as we are at the start of the line table.
   MCOS->EmitLabel(LineStartSym);
 
   // Create a symbol for the end of the section (to be set when we get there).
@@ -301,11 +334,7 @@ const MCSymbol *MCDwarfFileTable::Emit(MCStreamer *MCOS) {
        ++it) {
     const MCSection *Sec = *it;
     const MCLineSection *Line = MCLineSections.lookup(Sec);
-    EmitDwarfLineTable(MCOS, Sec, Line);
-
-    // Now delete the MCLineSections that were created in MCLineEntry::Make()
-    // and used to emit the line table.
-    delete Line;
+    EmitDwarfLineTable(MCOS, Sec, Line, CUID);
   }
 
   if (MCOS->getContext().getAsmInfo().getLinkerRequiresNonEmptyDwarfLines()