Enhance SymbolFileDWARF::ParseDeclsForContext performance

This implements
DWARFASTParserClang::EnsureAllDIEsInDeclContextHaveBeenParsed so as to
provide a faster way to ensure all DIEs linked to a certain declaration
context have been parsed.

Currently, we rely on SymbolFileDWARF::ParseDeclsForContext calling
DWARFASTParserClang::GetDIEForDeclContext, and only then
DWARFASTParserClang::GetDeclForUIDFromDWARF. This change shortcuts that
logic and removes redundant calls to DWARFASTParserClang::
GetClangDeclForDIE by deleting DIEs from the m_decl_ctx_to_die map once
they have been parsed.

Differential Revision: https://reviews.llvm.org/D67760
Patch by Guilherme Andrade <guiandrade@google.com>.

llvm-svn: 372744

4 files changed, 13 insertions, 19 deletions

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.h
index e7927b31b9c3..4f6885e61107 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.h
@@ -48,8 +48,8 @@ public:
   virtual lldb_private::CompilerDeclContext
   GetDeclContextContainingUIDFromDWARF(const DWARFDIE &die) = 0;
 
-  virtual std::vector<DWARFDIE>
-  GetDIEForDeclContext(lldb_private::CompilerDeclContext decl_context) = 0;
+  virtual void EnsureAllDIEsInDeclContextHaveBeenParsed(
+      lldb_private::CompilerDeclContext decl_context) = 0;
 
   static llvm::Optional<lldb_private::SymbolFile::ArrayInfo>
   ParseChildArrayInfo(const DWARFDIE &parent_die,
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 3c799f920a27..655246b499a0 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -2183,15 +2183,16 @@ bool DWARFASTParserClang::CompleteTypeFromDWARF(const DWARFDIE &die,
   return false;
 }
 
-std::vector<DWARFDIE> DWARFASTParserClang::GetDIEForDeclContext(
+void DWARFASTParserClang::EnsureAllDIEsInDeclContextHaveBeenParsed(
     lldb_private::CompilerDeclContext decl_context) {
-  std::vector<DWARFDIE> result;
   auto opaque_decl_ctx =
       (clang::DeclContext *)decl_context.GetOpaqueDeclContext();
   for (auto it = m_decl_ctx_to_die.find(opaque_decl_ctx);
-       it != m_decl_ctx_to_die.end() && it->first == opaque_decl_ctx; it++)
-    result.push_back(it->second);
-  return result;
+       it != m_decl_ctx_to_die.end() && it->first == opaque_decl_ctx;
+       it = m_decl_ctx_to_die.erase(it))
+    for (DWARFDIE decl = it->second.GetFirstChild(); decl;
+         decl = decl.GetSibling())
+      GetClangDeclForDIE(decl);
 }
 
 CompilerDecl DWARFASTParserClang::GetDeclForUIDFromDWARF(const DWARFDIE &die) {
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
index 5b5d83d65932..a8daa10596e5 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
@@ -51,8 +51,8 @@ public:
   lldb_private::CompilerDecl
   GetDeclForUIDFromDWARF(const DWARFDIE &die) override;
 
-  std::vector<DWARFDIE>
-  GetDIEForDeclContext(lldb_private::CompilerDeclContext decl_context) override;
+  void EnsureAllDIEsInDeclContextHaveBeenParsed(
+      lldb_private::CompilerDeclContext decl_context) override;
 
   lldb_private::CompilerDeclContext
   GetDeclContextForUIDFromDWARF(const DWARFDIE &die) override;
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 2177cbc89574..504fc2f7410c 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1217,16 +1217,9 @@ bool SymbolFileDWARF::ClassOrStructIsVirtual(const DWARFDIE &parent_die) {
 
 void SymbolFileDWARF::ParseDeclsForContext(CompilerDeclContext decl_ctx) {
   auto *type_system = decl_ctx.GetTypeSystem();
-  if (!type_system)
-    return;
-  DWARFASTParser *ast_parser = type_system->GetDWARFParser();
-  std::vector<DWARFDIE> decl_ctx_die_list =
-      ast_parser->GetDIEForDeclContext(decl_ctx);
-
-  for (DWARFDIE decl_ctx_die : decl_ctx_die_list)
-    for (DWARFDIE decl = decl_ctx_die.GetFirstChild(); decl;
-         decl = decl.GetSibling())
-      ast_parser->GetDeclForUIDFromDWARF(decl);
+  if (type_system != nullptr)
+    type_system->GetDWARFParser()->EnsureAllDIEsInDeclContextHaveBeenParsed(
+        decl_ctx);
 }
 
 user_id_t SymbolFileDWARF::GetUID(DIERef ref) {