DebugInfo: Avoid creating unnecessary/empty line tables and remove the special case of '0' in DwarfCompileUnit::initStmtList by just always using a label difference

This moves one case of raw text checking down into the MCStreamer
interfaces in the form of a virtual function, even if we ultimately end
up consolidating on the one-or-many line tables issue one day, this is
nicer in the interim. This just generally streamlines a bunch of use
cases into a common code path.

llvm-svn: 205287

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 0558a58abfd..8fa55aa59e2 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -191,6 +191,16 @@ void MCStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                   Discriminator);
 }
 
+MCSymbol *MCStreamer::getDwarfLineTableSymbol(unsigned CUID) {
+  MCDwarfLineTable &Table = getContext().getMCDwarfLineTable(CUID);
+  if (!Table.getLabel()) {
+    StringRef Prefix = Context.getAsmInfo()->getPrivateGlobalPrefix();
+    Table.setLabel(
+        Context.GetOrCreateSymbol(Prefix + "line_table_start" + Twine(CUID)));
+  }
+  return Table.getLabel();
+}
+
 MCDwarfFrameInfo *MCStreamer::getCurrentFrameInfo() {
   if (FrameInfos.empty())
     return 0;