Profiler: Cache parsed DWARF debug information in disassembly view

This changes browsing through disassembled functions in Profiler from a
painfully sluggish experience into quite a swift one. It's especially
true for profiling the kernel, as it has more than 10 megabytes of DWARF
data to churn through.

Userland/DevTools/Profiler/DisassemblyModel.cpp

@@ -54,7 +54,7 @@ DisassemblyModel::DisassemblyModel(Profile& profile, ProfileNode& node)
     , m_node(node)
 {
     FlatPtr base_address = 0;
-    OwnPtr<Debug::DebugInfo> debug_info;
+    const Debug::DebugInfo* debug_info;
     const ELF::Image* elf;
     if (auto maybe_kernel_base = Symbolication::kernel_base(); maybe_kernel_base.has_value() && m_node.address() >= *maybe_kernel_base) {
         if (!g_kernel_debuginfo_object.has_value())
@@ -63,7 +63,9 @@ DisassemblyModel::DisassemblyModel(Profile& profile, ProfileNode& node)
         elf = try_load_kernel_binary();
         if (elf == nullptr)
             return;
-        debug_info = make<Debug::DebugInfo>(g_kernel_debuginfo_object->elf, String::empty(), base_address);
+        if (g_kernel_debug_info == nullptr)
+            g_kernel_debug_info = make<Debug::DebugInfo>(g_kernel_debuginfo_object->elf, String::empty(), base_address);
+        debug_info = g_kernel_debug_info.ptr();
     } else {
         auto& process = node.process();
         auto library_data = process.library_metadata.library_containing(node.address());
@@ -73,7 +75,7 @@ DisassemblyModel::DisassemblyModel(Profile& profile, ProfileNode& node)
         }
         base_address = library_data->base;
         elf = &library_data->object->elf;
-        debug_info = make<Debug::DebugInfo>(library_data->object->elf, String::empty(), base_address);
+        debug_info = &library_data->load_debug_info(base_address);
     }
 
     VERIFY(elf != nullptr);

Userland/DevTools/Profiler/Process.cpp

@@ -102,10 +102,17 @@ void LibraryMetadata::handle_mmap(FlatPtr base, size_t size, const String& name)
             if (!mapped_object)
                 return;
         }
-        m_libraries.set(path_string, adopt_own(*new Library { base, size, path_string, mapped_object }));
+        m_libraries.set(path_string, adopt_own(*new Library { base, size, path_string, mapped_object, {} }));
     }
 }
 
+const Debug::DebugInfo& LibraryMetadata::Library::load_debug_info(FlatPtr base_address) const
+{
+    if (debug_info == nullptr)
+        debug_info = make<Debug::DebugInfo>(object->elf, String::empty(), base_address);
+    return *debug_info.ptr();
+}
+
 String LibraryMetadata::Library::symbolicate(FlatPtr ptr, u32* offset) const
 {
     if (!object)

Userland/DevTools/Profiler/Process.h

@@ -11,6 +11,7 @@
 #include <AK/MappedFile.h>
 #include <AK/OwnPtr.h>
 #include <AK/Vector.h>
+#include <LibDebug/DebugInfo.h>
 #include <LibELF/Image.h>
 
 namespace Profiler {
@@ -29,8 +30,11 @@ public:
         size_t size;
         String name;
         MappedObject* object { nullptr };
+        // This is loaded lazily because we only need it in disassembly view
+        mutable OwnPtr<Debug::DebugInfo> debug_info;
 
         String symbolicate(FlatPtr, u32* offset) const;
+        const Debug::DebugInfo& load_debug_info(FlatPtr base_address) const;
     };
 
     void handle_mmap(FlatPtr base, size_t size, const String& name);

Userland/DevTools/Profiler/Profile.cpp

@@ -212,6 +212,7 @@ void Profile::rebuild_tree()
 }
 
 Optional<MappedObject> g_kernel_debuginfo_object;
+OwnPtr<Debug::DebugInfo> g_kernel_debug_info;
 
 Result<NonnullOwnPtr<Profile>, String> Profile::load_from_perfcore_file(const StringView& path)
 {

Userland/DevTools/Profiler/Profile.h

@@ -29,6 +29,7 @@
 namespace Profiler {
 
 extern Optional<MappedObject> g_kernel_debuginfo_object;
+extern OwnPtr<Debug::DebugInfo> g_kernel_debug_info;
 
 class ProfileNode : public RefCounted<ProfileNode> {
 public: