[lldb] Implement LLDBMemoryReader::resolvePointer

Author: kastiglione

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.cpp

@@ -1,7 +1,9 @@
 #include "LLDBMemoryReader.h"
+#include "lldb/Core/Address.h"
 #include "lldb/Core/Section.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/Logging.h"
+#include "swift/Demangling/Demangle.h"
 
 #include "llvm/Support/MathExtras.h"
 
@@ -117,6 +119,29 @@ LLDBMemoryReader::getSymbolAddress(const std::string &name) {
   return swift::remote::RemoteAddress(load_addr);
 }
 
+swift::remote::RemoteAbsolutePointer
+LLDBMemoryReader::resolvePointer(swift::remote::RemoteAddress address,
+                                 uint64_t readValue) {
+  // If an address has a symbol, that symbol provides additional useful data to
+  // MetadataReader. Without the symbol, MetadataReader can derive the symbol
+  // by loading other parts of reflection metadata, but that work has a cost.
+  // For lldb, that data loading can be a significant performance hit. Providing
+  // a symbol greatly reduces memory read traffic to the process.
+  Address addr;
+  auto &target = m_process.GetTarget();
+  if (target.ResolveLoadAddress(address.getAddressData(), addr))
+    if (auto *symbol = addr.CalculateSymbolContextSymbol()) {
+      auto mangledName = symbol->GetMangled().GetMangledName().GetStringRef();
+      // MemoryReader requires any this to be a Swift symbol. LLDB can also be
+      // aware of local symbols, so avoid returning those.
+      if (swift::Demangle::isSwiftSymbol(mangledName))
+        return {mangledName, 0};
+    }
+
+  // Return the read value as is.
+  return {"", (int64_t)readValue};
+}
+
 bool LLDBMemoryReader::readBytes(swift::remote::RemoteAddress address,
                                  uint8_t *dest, uint64_t size) {
   if (m_local_buffer) {

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.h

@@ -23,6 +23,10 @@ class LLDBMemoryReader : public swift::remote::MemoryReader {
   swift::remote::RemoteAddress
   getSymbolAddress(const std::string &name) override;
 
+  swift::remote::RemoteAbsolutePointer
+  resolvePointer(swift::remote::RemoteAddress address,
+                 uint64_t readValue) override;
+
   bool readBytes(swift::remote::RemoteAddress address, uint8_t *dest,
                  uint64_t size) override;