Index: lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
===================================================================
--- lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
+++ lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
@@ -375,6 +375,46 @@
   return regnums.size();
 }
 
+static std::vector<DynamicRegisterInfo::Register> GetRegisters_x86_64() {
+  ConstString empty_alt_name;
+  ConstString reg_set{"general purpose registers"};
+
+#define R64(name)                                                              \
+  DynamicRegisterInfo::Register {                                              \
+    ConstString(#name), empty_alt_name, reg_set, 8, LLDB_INVALID_INDEX32,      \
+        lldb::eEncodingUint, lldb::eFormatHex, LLDB_INVALID_REGNUM,            \
+        LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, {}, {}, \
+  }
+#define R32(name)                                                              \
+  DynamicRegisterInfo::Register{                                               \
+      ConstString(#name),                                                      \
+      empty_alt_name,                                                          \
+      reg_set,                                                                 \
+      4,                                                                       \
+      LLDB_INVALID_INDEX32,                                                    \
+      lldb::eEncodingUint,                                                     \
+      lldb::eFormatHex,                                                        \
+      LLDB_INVALID_REGNUM,                                                     \
+      LLDB_INVALID_REGNUM,                                                     \
+      LLDB_INVALID_REGNUM,                                                     \
+      LLDB_INVALID_REGNUM,                                                     \
+      {},                                                                      \
+      {},                                                                      \
+  }
+
+  std::vector<DynamicRegisterInfo::Register> registers{
+      R64(rax), R64(rbx), R64(rcx), R64(rdx), R64(rsi), R64(rdi),
+      R64(rbp), R64(rsp), R64(r8),  R64(r9),  R64(r10), R64(r11),
+      R64(r12), R64(r13), R64(r14), R64(r15), R64(rip), R32(eflags),
+      R32(cs),  R32(ss),  R32(ds),  R32(es),  R32(fs),  R32(gs),
+  };
+
+#undef R32
+#undef R64
+
+  return registers;
+}
+
 void ProcessGDBRemote::BuildDynamicRegisterInfo(bool force) {
   if (!force && m_register_info_sp)
     return;
@@ -394,6 +434,7 @@
   //     2 - If the target definition doesn't have any of the info from the
   //     target.xml (registers) then proceed to read the target.xml.
   //     3 - Fall back on the qRegisterInfo packets.
+  //     4 - Use hardcoded defaults if available.
 
   FileSpec target_definition_fspec =
       GetGlobalPluginProperties().GetTargetDefinitionFile();
@@ -507,6 +548,18 @@
     }
   }
 
+  if (registers.empty()) {
+    switch (arch_to_use.GetMachine()) {
+    case llvm::Triple::x86:
+      break;
+    case llvm::Triple::x86_64:
+      registers = GetRegisters_x86_64();
+      break;
+    default:
+      break;
+    }
+  }
+
   AddRemoteRegisters(registers, arch_to_use);
 }