[LLDB][Formatters] Re-enable std::function formatter with fixes to improve non-cached lookup performance

Performance issues lead to the libc++ std::function formatter to be disabled. We addressed some of those performance issues by adding caching see D67111
This PR fixes the first lookup performance by not using FindSymbolsMatchingRegExAndType(...) and instead finding the compilation unit the std::function wrapped callable should be in and then searching for the callable directly in the CU.

Differential Revision: https://reviews.llvm.org/D69913

1 files changed, 121 insertions, 78 deletions

diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
index 379b0ba1b4d..b4d8ba2218a 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
@@ -21,6 +21,7 @@
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/UniqueCStringMap.h"
 #include "lldb/Symbol/ClangASTContext.h"
+#include "lldb/Symbol/CompileUnit.h"
 #include "lldb/Target/ABI.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/RegisterContext.h"
@@ -28,6 +29,7 @@
 #include "lldb/Target/StackFrame.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 #include "lldb/Target/ThreadPlanStepInRange.h"
+#include "lldb/Utility/Timer.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -58,9 +60,53 @@ bool CPPLanguageRuntime::GetObjectDescription(
   return false;
 }
 
+bool contains_lambda_identifier(llvm::StringRef &str_ref) {
+  return str_ref.contains("$_") || str_ref.contains("'lambda'");
+};
+
+CPPLanguageRuntime::LibCppStdFunctionCallableInfo
+line_entry_helper(Target &target, const SymbolContext &sc, Symbol *symbol,
+                  llvm::StringRef first_template_param_sref,
+                  bool has___invoke) {
+
+  CPPLanguageRuntime::LibCppStdFunctionCallableInfo optional_info;
+
+  AddressRange range;
+  sc.GetAddressRange(eSymbolContextEverything, 0, false, range);
+
+  Address address = range.GetBaseAddress();
+
+  Address addr;
+  if (target.ResolveLoadAddress(address.GetCallableLoadAddress(&target),
+                                addr)) {
+    LineEntry line_entry;
+    addr.CalculateSymbolContextLineEntry(line_entry);
+
+    if (contains_lambda_identifier(first_template_param_sref) || has___invoke) {
+      // Case 1 and 2
+      optional_info.callable_case = lldb_private::CPPLanguageRuntime::
+          LibCppStdFunctionCallableCase::Lambda;
+    } else {
+      // Case 3
+      optional_info.callable_case = lldb_private::CPPLanguageRuntime::
+          LibCppStdFunctionCallableCase::CallableObject;
+    }
+
+    optional_info.callable_symbol = *symbol;
+    optional_info.callable_line_entry = line_entry;
+    optional_info.callable_address = addr;
+  }
+
+  return optional_info;
+}
+
 CPPLanguageRuntime::LibCppStdFunctionCallableInfo
 CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
     lldb::ValueObjectSP &valobj_sp) {
+  static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
+  Timer scoped_timer(func_cat,
+                     "CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo");
+
   LibCppStdFunctionCallableInfo optional_info;
 
   if (!valobj_sp)
@@ -93,7 +139,7 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
   //    this entry and lookup operator()() and obtain the line table entry.
   // 3) a callable object via operator()(). We will obtain the name of the
   //    object from the first template parameter from __func's vtable. We will
-  //    look up the objectc operator()() and obtain the line table entry.
+  //    look up the objects operator()() and obtain the line table entry.
   // 4) a member function. A pointer to the function will stored after the
   //    we will obtain the name from this pointer.
   // 5) a free function. A pointer to the function will stored after the vtable
@@ -113,6 +159,9 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
 
   optional_info.member__f_pointer_value = member__f_pointer_value;
 
+  if (!member__f_pointer_value)
+    return optional_info;
+
   ExecutionContext exe_ctx(valobj_sp->GetExecutionContextRef());
   Process *process = exe_ctx.GetProcessPtr();
 
@@ -130,8 +179,14 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
   if (status.Fail())
     return optional_info;
 
+  lldb::addr_t vtable_address_first_entry =
+      process->ReadPointerFromMemory(vtable_address + address_size, status);
+
+  if (status.Fail())
+    return optional_info;
+
   lldb::addr_t address_after_vtable = member__f_pointer_value + address_size;
-  // As commened above we may not have a function pointer but if we do we will
+  // As commented above we may not have a function pointer but if we do we will
   // need it.
   lldb::addr_t possible_function_address =
       process->ReadPointerFromMemory(address_after_vtable, status);
@@ -144,9 +199,15 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
   if (target.GetSectionLoadList().IsEmpty())
     return optional_info;
 
+  Address vtable_first_entry_resolved;
+
+  if (!target.GetSectionLoadList().ResolveLoadAddress(
+          vtable_address_first_entry, vtable_first_entry_resolved))
+    return optional_info;
+
   Address vtable_addr_resolved;
   SymbolContext sc;
-  Symbol *symbol;
+  Symbol *symbol = nullptr;
 
   if (!target.GetSectionLoadList().ResolveLoadAddress(vtable_address,
                                                       vtable_addr_resolved))
@@ -159,7 +220,7 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
   if (symbol == nullptr)
     return optional_info;
 
-  llvm::StringRef vtable_name(symbol->GetName().GetCString());
+  llvm::StringRef vtable_name(symbol->GetName().GetStringRef());
   bool found_expected_start_string =
       vtable_name.startswith("vtable for std::__1::__function::__func<");
 
@@ -172,6 +233,11 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
   //  ... __func<main::$_0, std::__1::allocator<main::$_0> ...
   //             ^^^^^^^^^
   //
+  // We could see names such as:
+  //    main::$_0
+  //    Bar::add_num2(int)::'lambda'(int)
+  //    Bar
+  //
   // We do this by find the first < and , and extracting in between.
   //
   // This covers the case of the lambda known at compile time.
@@ -192,17 +258,29 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
         function_address_resolved, eSymbolContextEverything, sc);
     symbol = sc.symbol;
   }
-    
-    auto contains_lambda_identifier = []( llvm::StringRef & str_ref ) {
-        return str_ref.contains("$_") || str_ref.contains("'lambda'");
-    };
+
+  // These conditions are used several times to simplify statements later on.
+  bool has___invoke =
+      (symbol ? symbol->GetName().GetStringRef().contains("__invoke") : false);
+  auto calculate_symbol_context_helper = [](auto &t,
+                                            SymbolContextList &sc_list) {
+    SymbolContext sc;
+    t->CalculateSymbolContext(&sc);
+    sc_list.Append(sc);
+  };
+
+  // Case 2
+  if (has___invoke) {
+    SymbolContextList scl;
+    calculate_symbol_context_helper(symbol, scl);
+
+    return line_entry_helper(target, scl[0], symbol, first_template_parameter,
+                             has___invoke);
+  }
 
   // Case 4 or 5
-  // We eliminate these cases early because they don't need the potentially
-  // expensive lookup through the symbol table.
   if (symbol && !symbol->GetName().GetStringRef().startswith("vtable for") &&
-      !contains_lambda_identifier(first_template_parameter) &&
-      !symbol->GetName().GetStringRef().contains("__invoke")) {
+      !contains_lambda_identifier(first_template_parameter) && !has___invoke) {
     optional_info.callable_case =
         LibCppStdFunctionCallableCase::FreeOrMemberFunction;
     optional_info.callable_address = function_address_resolved;
@@ -211,41 +289,7 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
     return optional_info;
   }
 
-  auto get_name = [&first_template_parameter, &symbol, contains_lambda_identifier]() {
-    // Given case 1:
-    //
-    //    main::$_0
-    //    Bar::add_num2(int)::'lambda'(int)
-    //
-    // we want to append ::operator()()
-    if (contains_lambda_identifier(first_template_parameter))
-      return llvm::Regex::escape(first_template_parameter.str()) +
-             R"(::operator\(\)\(.*\))";
-
-    if (symbol != nullptr &&
-        symbol->GetName().GetStringRef().contains("__invoke")) {
-
-      llvm::StringRef symbol_name = symbol->GetName().GetStringRef();
-      size_t pos2 = symbol_name.find_last_of(':');
-
-      // Given case 2:
-      //
-      //    main::$_1::__invoke(...)
-      //
-      // We want to slice off __invoke(...) and append operator()()
-      std::string lambda_operator =
-          llvm::Regex::escape(symbol_name.slice(0, pos2 + 1).str()) +
-          R"(operator\(\)\(.*\))";
-
-      return lambda_operator;
-    }
-
-    // Case 3
-    return first_template_parameter.str() + R"(::operator\(\)\(.*\))";
-    ;
-  };
-
-  std::string func_to_match = get_name();
+  std::string func_to_match = first_template_parameter.str();
 
   auto it = CallableLookupCache.find(func_to_match);
   if (it != CallableLookupCache.end())
@@ -253,41 +297,40 @@ CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
 
   SymbolContextList scl;
 
-  target.GetImages().FindSymbolsMatchingRegExAndType(
-      RegularExpression{R"(^)" + func_to_match}, eSymbolTypeAny, scl);
+  CompileUnit *vtable_cu =
+      vtable_first_entry_resolved.CalculateSymbolContextCompileUnit();
+  llvm::StringRef name_to_use = func_to_match;
 
-  // Case 1,2 or 3
-  if (scl.GetSize() >= 1) {
-    SymbolContext sc2 = scl[0];
-
-    AddressRange range;
-    sc2.GetAddressRange(eSymbolContextEverything, 0, false, range);
-
-    Address address = range.GetBaseAddress();
-
-    Address addr;
-    if (target.ResolveLoadAddress(address.GetCallableLoadAddress(&target),
-                                  addr)) {
-      LineEntry line_entry;
-      addr.CalculateSymbolContextLineEntry(line_entry);
-
-      if (contains_lambda_identifier(first_template_parameter) ||
-          (symbol != nullptr &&
-           symbol->GetName().GetStringRef().contains("__invoke"))) {
-        // Case 1 and 2
-        optional_info.callable_case = LibCppStdFunctionCallableCase::Lambda;
-      } else {
-        // Case 3
-        optional_info.callable_case =
-            LibCppStdFunctionCallableCase::CallableObject;
-      }
-
-      optional_info.callable_symbol = *symbol;
-      optional_info.callable_line_entry = line_entry;
-      optional_info.callable_address = addr;
+  // Case 3, we have a callable object instead of a lambda
+  //
+  // TODO
+  // We currently don't support this case a callable object may have multiple
+  // operator()() varying on const/non-const and number of arguments and we
+  // don't have a way to currently distinguish them so we will bail out now.
+  if (!contains_lambda_identifier(name_to_use))
+    return optional_info;
+
+  if (vtable_cu && !has___invoke) {
+    lldb::FunctionSP func_sp =
+        vtable_cu->FindFunction([name_to_use](const FunctionSP &f) {
+          auto name = f->GetName().GetStringRef();
+          if (name.startswith(name_to_use) && name.contains("operator"))
+            return true;
+
+          return false;
+        });
+
+    if (func_sp) {
+      calculate_symbol_context_helper(func_sp, scl);
     }
   }
 
+  // Case 1 or 3
+  if (scl.GetSize() >= 1) {
+    optional_info = line_entry_helper(target, scl[0], symbol,
+                                      first_template_parameter, has___invoke);
+  }
+
   CallableLookupCache[func_to_match] = optional_info;
 
   return optional_info;