DebugInfo: Reapply r209984 (reverted in r210143), asserting that abstract DbgVariables have DIEs.

Abstract variables within abstract scopes that are entirely optimized
away in their first inlining are omitted because their scope is not
present so the variable is never created. Instead, we should ensure the
scope is created so the variable can be added, even if it's been
optimized away in its first inlining.

This fixes the incorrect debug info in missing-abstract-variable.ll
(added in r210143) and passes an asserts self-hosting build, so
hopefully there's not more of these issues left behind... *fingers
crossed*.

llvm-svn: 210221

3 files changed, 42 insertions, 14 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 73496b0c382..4dd36830a44 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1052,24 +1052,49 @@ DbgVariable *DwarfDebug::findAbstractVariable(DIVariable &DV,
   return findAbstractVariable(DV, ScopeLoc.getScope(DV->getContext()));
 }
 
-DbgVariable *DwarfDebug::findAbstractVariable(DIVariable &DV,
-                                              const MDNode *ScopeNode) {
+DbgVariable *DwarfDebug::getExistingAbstractVariable(DIVariable &DV,
+                                                     DIVariable &Cleansed) {
   LLVMContext &Ctx = DV->getContext();
   // More then one inlined variable corresponds to one abstract variable.
-  DIVariable Var = cleanseInlinedVariable(DV, Ctx);
-  auto I = AbstractVariables.find(Var);
+  // FIXME: This duplication of variables when inlining should probably be
+  // removed. It's done to allow each DIVariable to describe its location
+  // because the DebugLoc on the dbg.value/declare isn't accurate. We should
+  // make it accurate then remove this duplication/cleansing stuff.
+  Cleansed = cleanseInlinedVariable(DV, Ctx);
+  auto I = AbstractVariables.find(Cleansed);
   if (I != AbstractVariables.end())
     return I->second.get();
+  return nullptr;
+}
 
-  LexicalScope *Scope = LScopes.findAbstractScope(ScopeNode);
-  if (!Scope)
-    return nullptr;
-
+DbgVariable *DwarfDebug::createAbstractVariable(DIVariable &Var,
+                                                LexicalScope *Scope) {
   auto AbsDbgVariable = make_unique<DbgVariable>(Var, nullptr, this);
   addScopeVariable(Scope, AbsDbgVariable.get());
   return (AbstractVariables[Var] = std::move(AbsDbgVariable)).get();
 }
 
+DbgVariable *DwarfDebug::getOrCreateAbstractVariable(DIVariable &DV,
+                                                     const MDNode *ScopeNode) {
+  DIVariable Cleansed = DV;
+  if (DbgVariable *Var = getExistingAbstractVariable(DV, Cleansed))
+    return Var;
+
+  return createAbstractVariable(Cleansed,
+                                LScopes.getOrCreateAbstractScope(ScopeNode));
+}
+
+DbgVariable *DwarfDebug::findAbstractVariable(DIVariable &DV,
+                                              const MDNode *ScopeNode) {
+  DIVariable Cleansed = DV;
+  if (DbgVariable *Var = getExistingAbstractVariable(DV, Cleansed))
+    return Var;
+
+  if (LexicalScope *Scope = LScopes.findAbstractScope(ScopeNode))
+    return createAbstractVariable(Cleansed, Scope);
+  return nullptr;
+}
+
 // If Var is a current function argument then add it to CurrentFnArguments list.
 bool DwarfDebug::addCurrentFnArgument(DbgVariable *Var, LexicalScope *Scope) {
   if (!LScopes.isCurrentFunctionScope(Scope))
@@ -1513,7 +1538,7 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
       assert(DV && DV.isVariable());
       if (!ProcessedVars.insert(DV))
         continue;
-      findAbstractVariable(DV, DV.getContext());
+      getOrCreateAbstractVariable(DV, DV.getContext());
     }
     constructAbstractSubprogramScopeDIE(TheCU, AScope);
   }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 2d673791102..a3b0242fd5f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -343,6 +343,11 @@ class DwarfDebug : public AsmPrinterHandler {
   }
 
   /// \brief Find abstract variable associated with Var.
+  DbgVariable *getExistingAbstractVariable(DIVariable &DV,
+                                           DIVariable &Cleansed);
+  DbgVariable *createAbstractVariable(DIVariable &DV, LexicalScope *Scope);
+  DbgVariable *getOrCreateAbstractVariable(DIVariable &Var,
+                                           const MDNode *Scope);
   DbgVariable *findAbstractVariable(DIVariable &Var, DebugLoc Loc);
   DbgVariable *findAbstractVariable(DIVariable &Var, const MDNode *Scope);
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 2325ab8444e..0bac3bec389 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1782,12 +1782,10 @@ std::unique_ptr<DIE> DwarfUnit::constructVariableDIEImpl(const DbgVariable &DV,
   // Define variable debug information entry.
   auto VariableDie = make_unique<DIE>(DV.getTag());
   DbgVariable *AbsVar = DV.getAbstractVariable();
-  // FIXME: any missing abstract variable missing a DIE will result in incorrect
-  // DWARF. More details in test/DebugInfo/missing-abstract-variable.ll for an
-  // example of why this is happening.
-  if (AbsVar && AbsVar->getDIE())
+  if (AbsVar) {
+    assert(AbsVar->getDIE());
     addDIEEntry(*VariableDie, dwarf::DW_AT_abstract_origin, *AbsVar->getDIE());
-  else {
+  } else {
     if (!Name.empty())
       addString(*VariableDie, dwarf::DW_AT_name, Name);
     addSourceLine(*VariableDie, DV.getVariable());