DebugInfo: Following up to r209677, refactor local variable emission to delay the choice between emitting the definition attributes or using DW_AT_abstract_definition

This doesn't fix the abstract variable handling yet, but it introduces a
similar delay mechanism as was added for subprograms, causing
DW_AT_location to be reordered to the beginning of the attribute list
for local variables, and fixes all the test fallout for that.

A subsequent commit will remove the abstract variable handling in
DbgVariable and just do the abstract variable lookup at module end to
ensure that abstract variables introduced after their concrete
counterparts are appropriately referenced by the concrete variable.

llvm-svn: 210943
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 769ce9d..9538bee 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1514,6 +1514,17 @@
     addFlag(SPDie, dwarf::DW_AT_explicit);
 }
 
+void DwarfUnit::applyVariableAttributes(const DbgVariable &Var,
+                                        DIE &VariableDie) {
+  StringRef Name = Var.getName();
+  if (!Name.empty())
+    addString(VariableDie, dwarf::DW_AT_name, Name);
+  addSourceLine(VariableDie, Var.getVariable());
+  addType(VariableDie, Var.getType());
+  if (Var.isArtificial())
+    addFlag(VariableDie, dwarf::DW_AT_artificial);
+}
+
 // Return const expression if value is a GEP to access merged global
 // constant. e.g.
 // i8* getelementptr ({ i8, i8, i8, i8 }* @_MergedGlobals, i32 0, i32 0)
@@ -1787,24 +1798,13 @@
 
 std::unique_ptr<DIE> DwarfUnit::constructVariableDIEImpl(const DbgVariable &DV,
                                                          bool Abstract) {
-  StringRef Name = DV.getName();
-
   // Define variable debug information entry.
   auto VariableDie = make_unique<DIE>(DV.getTag());
-  DbgVariable *AbsVar = DV.getAbstractVariable();
-  if (AbsVar && AbsVar->getDIE()) {
-    addDIEEntry(*VariableDie, dwarf::DW_AT_abstract_origin, *AbsVar->getDIE());
-  } else {
-    if (!Name.empty())
-      addString(*VariableDie, dwarf::DW_AT_name, Name);
-    addSourceLine(*VariableDie, DV.getVariable());
-    addType(*VariableDie, DV.getType());
-    if (DV.isArtificial())
-      addFlag(*VariableDie, dwarf::DW_AT_artificial);
-  }
 
-  if (Abstract)
+  if (Abstract) {
+    applyVariableAttributes(DV, *VariableDie);
     return VariableDie;
+  }
 
   // Add variable address.