Turn on pubnames by default on linux.

Until gdb supports the new accelerator tables we should add the
pubnames section so that gdb_index can be generated from gold
at link time. On darwin we already emit the accelerator tables
and so don't need to worry about pubnames.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188708 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 8fd208a..1de4fca 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -58,11 +58,6 @@
     cl::init(false));
 
 static cl::opt<bool>
-GenerateDwarfPubNamesSection("generate-dwarf-pubnames", cl::Hidden,
-                             cl::init(false),
-                             cl::desc("Generate DWARF pubnames section"));
-
-static cl::opt<bool>
 GenerateODRHash("generate-odr-hash", cl::Hidden,
                 cl::desc("Add an ODR hash to external type DIEs."),
                 cl::init(false));
@@ -104,6 +99,14 @@
                       clEnumVal(Disable, "Disabled"), clEnumValEnd),
            cl::init(Default));
 
+static cl::opt<DefaultOnOff>
+DwarfPubNames("generate-dwarf-pubnames", cl::Hidden,
+              cl::desc("Generate DWARF pubnames section"),
+              cl::values(clEnumVal(Default, "Default for platform"),
+                         clEnumVal(Enable, "Enabled"),
+                         clEnumVal(Disable, "Disabled"), clEnumValEnd),
+              cl::init(Default));
+
 namespace {
   const char *const DWARFGroupName = "DWARF Emission";
   const char *const DbgTimerName = "DWARF Debug Writer";
@@ -225,6 +228,14 @@
   else
     HasSplitDwarf = SplitDwarf == Enable ? true : false;
 
+  if (DwarfPubNames == Default) {
+    if (IsDarwin)
+      HasDwarfPubNames = false;
+    else
+      HasDwarfPubNames = true;
+  } else
+    HasDwarfPubNames = DwarfPubNames == Enable ? true : false;
+
   DwarfVersion = getDwarfVersionFromModule(MMI->getModule());
 
   {
@@ -797,7 +808,7 @@
   TheCU->addToContextOwner(SubprogramDie, SP.getContext());
 
   // Expose as global, if requested.
-  if (GenerateDwarfPubNamesSection)
+  if (HasDwarfPubNames)
     TheCU->addGlobalName(SP.getName(), SubprogramDie);
 }
 
@@ -1146,7 +1157,7 @@
   }
 
   // Emit info into a debug pubnames section, if requested.
-  if (GenerateDwarfPubNamesSection)
+  if (HasDwarfPubNames)
     emitDebugPubnames();
 
   // Emit info into a debug pubtypes section.
@@ -1932,7 +1943,7 @@
   DwarfLineSectionSym =
     emitSectionSym(Asm, TLOF.getDwarfLineSection(), "section_line");
   emitSectionSym(Asm, TLOF.getDwarfLocSection());
-  if (GenerateDwarfPubNamesSection)
+  if (HasDwarfPubNames)
     emitSectionSym(Asm, TLOF.getDwarfPubNamesSection());
   emitSectionSym(Asm, TLOF.getDwarfPubTypesSection());
   DwarfStrSectionSym =
@@ -2307,8 +2318,8 @@
       continue;
 
     // Start the dwarf pubnames section.
-    Asm->OutStreamer.SwitchSection(
-      Asm->getObjFileLowering().getDwarfPubNamesSection());
+    Asm->OutStreamer
+        .SwitchSection(Asm->getObjFileLowering().getDwarfPubNamesSection());
 
     Asm->OutStreamer.AddComment("Length of Public Names Info");
     Asm->EmitLabelDifference(Asm->GetTempSymbol("pubnames_end", ID),