Provide a mechanism to do some pre-loading of symbols up front.

Loading a shared library can require a large amount of work; rather than do that serially for each library,
this patch will allow parallelization of the symbols and debug info name indexes.

From scott.smith@purestorage.com

https://reviews.llvm.org/D32598

llvm-svn: 301609

lldb/include/lldb/Core/Module.h

@@ -614,6 +614,8 @@ public:
 
   const FileSpec &GetSymbolFileFileSpec() const { return m_symfile_spec; }
 
+  void PreloadSymbols();
+
   void SetSymbolFileFileSpec(const FileSpec &file);
 
   const llvm::sys::TimePoint<> &GetModificationTime() const {

lldb/include/lldb/Symbol/SymbolFile.h

@@ -180,6 +180,8 @@ public:
                           uint32_t type_mask,
                           lldb_private::TypeList &type_list) = 0;
 
+  virtual void PreloadSymbols();
+
   virtual lldb_private::TypeSystem *
   GetTypeSystemForLanguage(lldb::LanguageType language);
 

lldb/include/lldb/Symbol/Symtab.h

@@ -40,6 +40,7 @@ public:
   Symtab(ObjectFile *objfile);
   ~Symtab();
 
+  void PreloadSymbols();
   void Reserve(size_t count);
   Symbol *Resize(size_t count);
   uint32_t AddSymbol(const Symbol &symbol);

lldb/include/lldb/Target/Target.h

@@ -82,6 +82,10 @@ public:
 
   bool SetPreferDynamicValue(lldb::DynamicValueType d);
 
+  bool GetPreloadSymbols() const;
+
+  void SetPreloadSymbols(bool b);
+
   bool GetDisableASLR() const;
 
   void SetDisableASLR(bool b);

lldb/packages/Python/lldbsuite/test/lang/c/shared_lib/TestSharedLib.py

@@ -13,14 +13,13 @@ class SharedLibTestCase(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
 
-    def test_expr(self):
-        """Test that types work when defined in a shared library and forward-declared in the main executable"""
+    def common_test_expr(self, preload_symbols):
         if "clang" in self.getCompiler() and "3.4" in self.getCompilerVersion():
             self.skipTest(
                 "llvm.org/pr16214 -- clang emits partial DWARF for structures referenced via typedef")
 
         self.build()
-        self.common_setup()
+        self.common_setup(preload_symbols)
 
         # This should display correctly.
         self.expect(
@@ -31,6 +30,18 @@ class SharedLibTestCase(TestBase):
                 "(sub_foo)",
                 "other_element = 3"])
 
+        self.expect(
+            "expression GetMeASubFoo(my_foo_ptr)",
+            startstr="(sub_foo *) $")
+
+    def test_expr(self):
+        """Test that types work when defined in a shared library and forward-declared in the main executable"""
+        self.common_test_expr(True)
+
+    def test_expr_no_preload(self):
+        """Test that types work when defined in a shared library and forward-declared in the main executable, but with preloading disabled"""
+        self.common_test_expr(False)
+
     @unittest2.expectedFailure("rdar://problem/10704639")
     def test_frame_variable(self):
         """Test that types work when defined in a shared library and forward-declared in the main executable"""
@@ -54,7 +65,7 @@ class SharedLibTestCase(TestBase):
         self.line = line_number(self.source, '// Set breakpoint 0 here.')
         self.shlib_names = ["foo"]
 
-    def common_setup(self):
+    def common_setup(self, preload_symbols = True):
         # Run in synchronous mode
         self.dbg.SetAsync(False)
 
@@ -62,6 +73,8 @@ class SharedLibTestCase(TestBase):
         target = self.dbg.CreateTarget("a.out")
         self.assertTrue(target, VALID_TARGET)
 
+        self.runCmd("settings set target.preload-symbols " + str(preload_symbols).lower())
+
         # Break inside the foo function which takes a bar_ptr argument.
         lldbutil.run_break_set_by_file_and_line(
             self, self.source, self.line, num_expected_locations=1, loc_exact=True)

lldb/source/Core/Module.cpp

@@ -1432,6 +1432,22 @@ size_t Module::FindSymbolsMatchingRegExAndType(const RegularExpression &regex,
   return sc_list.GetSize() - initial_size;
 }
 
+void Module::PreloadSymbols() {
+  std::lock_guard<std::recursive_mutex> guard(m_mutex);
+  SymbolVendor * sym_vendor = GetSymbolVendor();
+  if (!sym_vendor) {
+    return;
+  }
+  // Prime the symbol file first, since it adds symbols to the symbol table.
+  if (SymbolFile *symbol_file = sym_vendor->GetSymbolFile()) {
+    symbol_file->PreloadSymbols();
+  }
+  // Now we can prime the symbol table.
+  if (Symtab * symtab = sym_vendor->GetSymtab()) {
+    symtab->PreloadSymbols();
+  }
+}
+
 void Module::SetSymbolFileFileSpec(const FileSpec &file) {
   if (!file.Exists())
     return;

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -1917,6 +1917,12 @@ uint32_t SymbolFileDWARF::ResolveSymbolContext(const FileSpec &file_spec,
   return sc_list.GetSize() - prev_size;
 }
 
+void SymbolFileDWARF::PreloadSymbols() {
+  std::lock_guard<std::recursive_mutex> guard(
+      GetObjectFile()->GetModule()->GetMutex());
+  Index();
+}
+
 void SymbolFileDWARF::Index() {
   if (m_indexed)
     return;

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

@@ -226,6 +226,8 @@ public:
       const lldb_private::ConstString &name,
       const lldb_private::CompilerDeclContext *parent_decl_ctx) override;
 
+  void PreloadSymbols() override;
+
   //------------------------------------------------------------------
   // PluginInterface protocol
   //------------------------------------------------------------------

lldb/source/Symbol/SymbolFile.cpp

@@ -21,6 +21,10 @@
 
 using namespace lldb_private;
 
+void SymbolFile::PreloadSymbols() {
+  // No-op for most implementations.
+}
+
 SymbolFile *SymbolFile::FindPlugin(ObjectFile *obj_file) {
   std::unique_ptr<SymbolFile> best_symfile_ap;
   if (obj_file != nullptr) {

lldb/source/Symbol/Symtab.cpp

@@ -427,6 +427,11 @@ void Symtab::InitNameIndexes() {
   }
 }
 
+void Symtab::PreloadSymbols() {
+  std::lock_guard<std::recursive_mutex> guard(m_mutex);
+  InitNameIndexes();
+}
+
 void Symtab::AppendSymbolNamesToMap(const IndexCollection &indexes,
                                     bool add_demangled, bool add_mangled,
                                     NameToIndexMap &name_to_index_map) const {

lldb/source/Target/Target.cpp

@@ -1870,6 +1870,11 @@ ModuleSP Target::GetSharedModule(const ModuleSpec &module_spec,
           }
         }
 
+        // Preload symbols outside of any lock, so hopefully we can do this for
+        // each library in parallel.
+        if (GetPreloadSymbols())
+          module_sp->PreloadSymbols();
+
         if (old_module_sp &&
             m_images.GetIndexForModule(old_module_sp.get()) !=
                 LLDB_INVALID_INDEX32) {
@@ -3277,6 +3282,8 @@ static PropertyDefinition g_properties[] = {
     {"detach-on-error", OptionValue::eTypeBoolean, false, true, nullptr,
      nullptr, "debugserver will detach (rather than killing) a process if it "
               "loses connection with lldb."},
+    {"preload-symbols", OptionValue::eTypeBoolean, false, true, nullptr, nullptr,
+     "Enable loading of symbol tables before they are needed."},
     {"disable-aslr", OptionValue::eTypeBoolean, false, true, nullptr, nullptr,
      "Disable Address Space Layout Randomization (ASLR)"},
     {"disable-stdio", OptionValue::eTypeBoolean, false, false, nullptr, nullptr,
@@ -3379,6 +3386,7 @@ enum {
   ePropertyOutputPath,
   ePropertyErrorPath,
   ePropertyDetachOnError,
+  ePropertyPreloadSymbols,
   ePropertyDisableASLR,
   ePropertyDisableSTDIO,
   ePropertyInlineStrategy,
@@ -3641,6 +3649,17 @@ bool TargetProperties::SetPreferDynamicValue(lldb::DynamicValueType d) {
   return m_collection_sp->SetPropertyAtIndexAsEnumeration(nullptr, idx, d);
 }
 
+bool TargetProperties::GetPreloadSymbols() const {
+  const uint32_t idx = ePropertyPreloadSymbols;
+  return m_collection_sp->GetPropertyAtIndexAsBoolean(
+      nullptr, idx, g_properties[idx].default_uint_value != 0);
+}
+
+void TargetProperties::SetPreloadSymbols(bool b) {
+  const uint32_t idx = ePropertyPreloadSymbols;
+  m_collection_sp->SetPropertyAtIndexAsBoolean(nullptr, idx, b);
+}
+
 bool TargetProperties::GetDisableASLR() const {
   const uint32_t idx = ePropertyDisableASLR;
   return m_collection_sp->GetPropertyAtIndexAsBoolean(