[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, 5 insertions, 4 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
index 8a6a58c5545..9da481979f7 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
@@ -301,13 +301,14 @@ ThreadGDBRemote::CreateRegisterContextForFrame(StackFrame *frame) {
     if (process_sp) {
       ProcessGDBRemote *gdb_process =
           static_cast<ProcessGDBRemote *>(process_sp.get());
-      // read_all_registers_at_once will be true if 'p' packet is not
-      // supported.
+      bool pSupported =
+          gdb_process->GetGDBRemote().GetpPacketSupported(GetID());
       bool read_all_registers_at_once =
-          !gdb_process->GetGDBRemote().GetpPacketSupported(GetID());
+          !pSupported || gdb_process->m_use_g_packet_for_reading;
+      bool write_all_registers_at_once = !pSupported;
       reg_ctx_sp = std::make_shared<GDBRemoteRegisterContext>(
           *this, concrete_frame_idx, gdb_process->m_register_info,
-          read_all_registers_at_once);
+          read_all_registers_at_once, write_all_registers_at_once);
     }
   } else {
     Unwind *unwinder = GetUnwinder();