[lldb-server] Add setting to force 'g' packet use

Following up on https://reviews.llvm.org/D62221, this change introduces
the settings plugin.process.gdb-remote.use-g-packet-for-reading.  When
they are on, 'g' packets are used for reading registers.

Using 'g' packets can improve performance by reducing the number of
packets exchanged between client and server when a large number of
registers needs to be fetched.

Differential revision: https://reviews.llvm.org/D62931

1 files changed, 8 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
index f1762abc55f..9e459cf3382 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
@@ -154,6 +154,11 @@ public:
         nullptr, idx,
         g_processgdbremote_properties[idx].default_uint_value != 0);
   }
+
+  bool GetUseGPacketForReading() const {
+    const uint32_t idx = ePropertyUseGPacketForReading;
+    return m_collection_sp->GetPropertyAtIndexAsBoolean(nullptr, idx, true);
+  }
 };
 
 typedef std::shared_ptr<PluginProperties> ProcessKDPPropertiesSP;
@@ -309,6 +314,9 @@ ProcessGDBRemote::ProcessGDBRemote(lldb::TargetSP target_sp,
       GetGlobalPluginProperties()->GetPacketTimeout();
   if (timeout_seconds > 0)
     m_gdb_comm.SetPacketTimeout(std::chrono::seconds(timeout_seconds));
+
+  m_use_g_packet_for_reading =
+      GetGlobalPluginProperties()->GetUseGPacketForReading();
 }
 
 // Destructor