From 5113cdbfff7df4c7a79a92e5aa971126254202c6 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Fri, 3 Dec 2010 00:10:48 +0000
Subject: [PATCH] It may not be an option to skip .debug_line if there are file
 reference in already emitted debug info. So, for now, emit dummy line table
 entry to make older linker and assemblers happy. This is not a new behavior,
 original AsmPrinter emitted similar line table entries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120760 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/MC/MCContext.h |  3 ---
 include/llvm/MC/MCDwarf.h   |  3 ++-
 lib/MC/MCAsmStreamer.cpp    |  4 ++--
 lib/MC/MCDwarf.cpp          | 20 +++++++++++++++++++-
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/llvm/MC/MCContext.h b/include/llvm/MC/MCContext.h
index 575bc3b2971..7968e1e27d9 100644
--- a/include/llvm/MC/MCContext.h
+++ b/include/llvm/MC/MCContext.h
@@ -180,9 +180,6 @@ namespace llvm {
     bool hasDwarfFiles() const {
       return !MCDwarfFiles.empty();
     }
-    bool hasDwarfLines() const {
-      return !MCLineSectionOrder.empty();
-    }
 
     const std::vector<MCDwarfFile *> &getMCDwarfFiles() {
       return MCDwarfFiles;
diff --git a/include/llvm/MC/MCDwarf.h b/include/llvm/MC/MCDwarf.h
index 52371f69792..0c0a22eb8ab 100644
--- a/include/llvm/MC/MCDwarf.h
+++ b/include/llvm/MC/MCDwarf.h
@@ -209,7 +209,8 @@ namespace llvm {
     // This emits the Dwarf file and the line tables.
     //
     static void Emit(MCStreamer *MCOS, const MCSection *DwarfLineSection,
-                     MCSectionData *DLS, int PointerSize);
+                     MCSectionData *DLS, int PointerSize,
+                     const MCSection *TextSection = NULL);
   };
 
   class MCDwarfLineAddr {
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index 30a3105bd79..49bcc936f7a 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -885,9 +885,9 @@ void MCAsmStreamer::EmitRawText(StringRef String) {
 
 void MCAsmStreamer::Finish() {
   // Dump out the dwarf file & directory tables and line tables.
-  if (getContext().hasDwarfFiles() && getContext().hasDwarfLines() && TLOF) {
+  if (getContext().hasDwarfFiles() && TLOF) {
     MCDwarfFileTable::Emit(this, TLOF->getDwarfLineSection(), NULL,
-                           PointerSize);
+                           PointerSize, TLOF->getTextSection());
   }
 }
 
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 0daf2959e33..5fe73e2810a 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -241,7 +241,8 @@ static inline void EmitDwarfLineTable(MCStreamer *MCOS,
 void MCDwarfFileTable::Emit(MCStreamer *MCOS,
                             const MCSection *DwarfLineSection,
                             MCSectionData *DLS,
-                            int PointerSize) {
+                            int PointerSize,
+                            const MCSection *TextSection) {
   // Switch to the section where the table will be emitted into.
   MCOS->SwitchSection(DwarfLineSection);
 
@@ -339,6 +340,23 @@ void MCDwarfFileTable::Emit(MCStreamer *MCOS,
     delete Line;
   }
 
+  if (TextSection && MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
+    // Emit dummy entry if line table is empty.
+
+    MCOS->SwitchSection(TextSection);
+    MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
+    // Set the value of the symbol, as we are at the end of the section.
+    MCOS->EmitLabel(SectionEnd);
+
+    // Switch back the the dwarf line section.
+    MCOS->SwitchSection(DwarfLineSection);
+
+    // emit the sequence to set the address
+    EmitDwarfSetAddress(MCOS, SectionEnd, PointerSize);
+    // emit the sequence for the LineDelta (from 1) and a zero address delta.
+    MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
+  }
+
   // This is the end of the section, so set the value of the symbol at the end
   // of this section (that was used in a previous expression).
   MCOS->EmitLabel(LineEndSym);