Simplify DINamespace caching in CGDebugInfo

This addresses review feedback from r302840.

By not canonicalizing namespace decls and using lexical decl context
instead of lookuing up the semantic decl context we can take advantage
of the fact that DINamespaces a reuniqued. This way non-module debug
info is unchanged and module debug info still gets distinct namespace
declarations when they ocur in different modules.

Thanks to Richard Smith for pointing this out!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302915 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 22 deletions

diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index d15ae06b45..9d77c61bd5 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -208,10 +208,8 @@ llvm::DIScope *CGDebugInfo::getContextDescriptor(const Decl *Context,
   }
 
   // Check namespace.
-  if (const auto *NSDecl = dyn_cast<NamespaceDecl>(Context)) {
-    auto *ParentModule = dyn_cast<llvm::DIModule>(Default);
-    return getOrCreateNamespace(NSDecl, ParentModule);
-  }
+  if (const auto *NSDecl = dyn_cast<NamespaceDecl>(Context))
+    return getOrCreateNamespace(NSDecl);
 
   if (const auto *RDecl = dyn_cast<RecordDecl>(Context))
     if (!RDecl->isDependentType())
@@ -2862,8 +2860,8 @@ void CGDebugInfo::collectFunctionDeclProps(GlobalDecl GD, llvm::DIFile *Unit,
 
   if (DebugKind >= codegenoptions::LimitedDebugInfo) {
     if (const NamespaceDecl *NSDecl =
-        dyn_cast_or_null<NamespaceDecl>(FD->getDeclContext()))
-    FDContext = getOrCreateNamespace(NSDecl, getParentModuleOrNull(FD));
+        dyn_cast_or_null<NamespaceDecl>(FD->getLexicalDeclContext()))
+      FDContext = getOrCreateNamespace(NSDecl);
     else if (const RecordDecl *RDecl =
              dyn_cast_or_null<RecordDecl>(FD->getDeclContext())) {
       llvm::DIScope *Mod = getParentModuleOrNull(RDecl);
@@ -3963,7 +3961,7 @@ void CGDebugInfo::EmitUsingDirective(const UsingDirectiveDecl &UD) {
       CGM.getCodeGenOpts().DebugExplicitImport) {
     DBuilder.createImportedModule(
         getCurrentContextDescriptor(cast<Decl>(UD.getDeclContext())),
-        getOrCreateNamespace(NSDecl, getParentModuleOrNull(&UD)),
+        getOrCreateNamespace(NSDecl),
         getLineNumber(UD.getLocation()));
   }
 }
@@ -4023,32 +4021,26 @@ CGDebugInfo::EmitNamespaceAlias(const NamespaceAliasDecl &NA) {
   else
     R = DBuilder.createImportedDeclaration(
         getCurrentContextDescriptor(cast<Decl>(NA.getDeclContext())),
-        getOrCreateNamespace(cast<NamespaceDecl>(NA.getAliasedNamespace()),
-                             getParentModuleOrNull(&NA)),
+        getOrCreateNamespace(cast<NamespaceDecl>(NA.getAliasedNamespace())),
         getLineNumber(NA.getLocation()), NA.getName());
   VH.reset(R);
   return R;
 }
 
 llvm::DINamespace *
-CGDebugInfo::getOrCreateNamespace(const NamespaceDecl *NSDecl,
-                                  llvm::DIModule *ParentModule) {
-  NSDecl = NSDecl->getCanonicalDecl();
-  // The AST merges NamespaceDecls, but for module debug info it is important to
-  // put a namespace decl (or rather its children) into the correct
-  // (sub-)module, so use the parent module of the decl that triggered this
-  // namespace to be serialized as a second key.
-  NamespaceKey Key = {NSDecl, ParentModule};
-  auto I = NamespaceCache.find(Key);
+CGDebugInfo::getOrCreateNamespace(const NamespaceDecl *NSDecl) {
+  // Don't canonicalize the NamespaceDecl here: The DINamespace will be uniqued
+  // if necessary, and this way multiple declarations of the same namespace in
+  // different parent modules stay distinct.
+  auto I = NamespaceCache.find(NSDecl);
   if (I != NamespaceCache.end())
     return cast<llvm::DINamespace>(I->second);
 
   llvm::DIScope *Context = getDeclContextDescriptor(NSDecl);
   // Don't trust the context if it is a DIModule (see comment above).
-  llvm::DINamespace *NS = DBuilder.createNameSpace(
-      isa<llvm::DIModule>(Context) ? ParentModule : Context, NSDecl->getName(),
-      NSDecl->isInline());
-  NamespaceCache[Key].reset(NS);
+  llvm::DINamespace *NS =
+      DBuilder.createNameSpace(Context, NSDecl->getName(), NSDecl->isInline());
+  NamespaceCache[NSDecl].reset(NS);
   return NS;
 }