DebugInfo: Do not rely on the compilation dir (index 0) for files in line tables shared between compilation units

When emitting assembly there's no support for emitting separate line
tables for each compilation unit - so LLVM emits .loc directives
producing a single line table.

Line tables have an implicit directory (index 0) equal to the
compilation directory (DW_AT_comp_dir) of the compilation unit that
references them.

If multiple compilation units (with possibly disparate compilation
directories) reference the same line table, we must avoid relying on
this ambiguous directory.

Achieve this my simply not setting the compilation directory on the line
table when we're in this situation (multiple units while emitting
assembly).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204094 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 13 insertions, 6 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 8c499f8493..77765e12f8 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -674,7 +674,8 @@ void DwarfDebug::addGnuPubAttributes(DwarfUnit *U, DIE *D) const {
 
 // Create new DwarfCompileUnit for the given metadata node with tag
 // DW_TAG_compile_unit.
-DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
+DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit,
+                                                        bool Singular) {
   StringRef FN = DIUnit.getFilename();
   CompilationDir = DIUnit.getDirectory();
 
@@ -682,8 +683,9 @@ DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
   DwarfCompileUnit *NewCU = new DwarfCompileUnit(
       InfoHolder.getUnits().size(), Die, DIUnit, Asm, this, &InfoHolder);
   InfoHolder.addUnit(NewCU);
-  Asm->OutStreamer.getContext().setMCLineTableCompilationDir(
-      NewCU->getUniqueID(), CompilationDir);
+  if (!Asm->OutStreamer.hasRawTextSupport() || Singular)
+    Asm->OutStreamer.getContext().setMCLineTableCompilationDir(
+        NewCU->getUniqueID(), CompilationDir);
 
   NewCU->addString(Die, dwarf::DW_AT_producer, DIUnit.getProducer());
   NewCU->addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
@@ -814,9 +816,13 @@ void DwarfDebug::beginModule() {
   // Emit initial sections so we can reference labels later.
   emitSectionLabels();
 
-  for (MDNode *N : CU_Nodes->operands()) {
+  auto Operands = CU_Nodes->operands();
+
+  bool SingleCU = std::next(Operands.begin()) == Operands.end();
+
+  for (MDNode *N : Operands) {
     DICompileUnit CUNode(N);
-    DwarfCompileUnit *CU = constructDwarfCompileUnit(CUNode);
+    DwarfCompileUnit *CU = constructDwarfCompileUnit(CUNode, SingleCU);
     DIArray ImportedEntities = CUNode.getImportedEntities();
     for (unsigned i = 0, e = ImportedEntities.getNumElements(); i != e; ++i)
       ScopesWithImportedEntities.push_back(std::make_pair(
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 7f4ed6e290..71ff75d640 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -630,7 +630,8 @@ class DwarfDebug : public AsmPrinterHandler {
 
   /// \brief Create new DwarfCompileUnit for the given metadata node with tag
   /// DW_TAG_compile_unit.
-  DwarfCompileUnit *constructDwarfCompileUnit(DICompileUnit DIUnit);
+  DwarfCompileUnit *constructDwarfCompileUnit(DICompileUnit DIUnit,
+                                              bool Singular);
 
   /// \brief Construct subprogram DIE.
   void constructSubprogramDIE(DwarfCompileUnit *TheCU, const MDNode *N);