diff --git a/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.h b/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.h
--- a/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.h
+++ b/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.h
@@ -38,6 +38,11 @@
   void AddRegister(lldb_private::RegisterInfo reg_info,
                    lldb_private::ConstString &set_name);
 
+  // Add a new register and cross-link it via invalidate_regs with other
+  // registers sharing its value_regs.
+  void AddSupplementaryRegister(lldb_private::RegisterInfo reg_info,
+                                lldb_private::ConstString &set_name);
+
   void Finalize(const lldb_private::ArchSpec &arch);
 
   size_t GetNumRegisters() const;
diff --git a/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.cpp b/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.cpp
--- a/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.cpp
+++ b/lldb/source/Plugins/Process/Utility/DynamicRegisterInfo.cpp
@@ -430,6 +430,29 @@
   m_set_reg_nums[set].push_back(reg_num);
 }
 
+void DynamicRegisterInfo::AddSupplementaryRegister(RegisterInfo new_reg_info,
+                                                   ConstString &set_name) {
+  assert(new_reg_info.value_regs != nullptr);
+  const uint32_t reg_num = m_regs.size();
+  AddRegister(new_reg_info, set_name);
+
+  reg_to_regs_map new_invalidates;
+  for (uint32_t value_reg : m_value_regs_map[reg_num]) {
+    // copy value_regs to invalidate_regs
+    new_invalidates[reg_num].push_back(value_reg);
+
+    // copy invalidate_regs from the parent register
+    llvm::append_range(new_invalidates[reg_num], m_invalidate_regs_map[value_reg]);
+
+    // add reverse invalidate entries
+    for (uint32_t x : new_invalidates[reg_num])
+      new_invalidates[x].push_back(new_reg_info.kinds[eRegisterKindLLDB]);
+  }
+
+  for (const auto &x : new_invalidates)
+    llvm::append_range(m_invalidate_regs_map[x.first], x.second);
+}
+
 void DynamicRegisterInfo::Finalize(const ArchSpec &arch) {
   if (m_finalized)
     return;
diff --git a/lldb/unittests/Process/Utility/DynamicRegisterInfoTest.cpp b/lldb/unittests/Process/Utility/DynamicRegisterInfoTest.cpp
--- a/lldb/unittests/Process/Utility/DynamicRegisterInfoTest.cpp
+++ b/lldb/unittests/Process/Utility/DynamicRegisterInfoTest.cpp
@@ -124,3 +124,47 @@
   ASSERT_REG(i1, LLDB_INVALID_INDEX32);
   ASSERT_REG(i2, LLDB_INVALID_INDEX32);
 }
+
+TEST_F(DynamicRegisterInfoTest, add_supplementary_register) {
+  // Add a base register
+  uint32_t rax = AddTestRegister("rax", 8);
+
+  // Register numbers
+  uint32_t eax = 1;
+  uint32_t ax = 2;
+  uint32_t al = 3;
+
+  ConstString group{"supplementary registers"};
+  uint32_t value_regs[2] = {rax, LLDB_INVALID_REGNUM};
+  struct RegisterInfo eax_reg {
+    "eax", nullptr, 4, LLDB_INVALID_INDEX32, lldb::eEncodingUint,
+        lldb::eFormatUnsigned,
+        {LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, eax,
+         eax},
+        value_regs, nullptr, nullptr, 0
+  };
+  info.AddSupplementaryRegister(eax_reg, group);
+
+  struct RegisterInfo ax_reg {
+    "ax", nullptr, 2, LLDB_INVALID_INDEX32, lldb::eEncodingUint,
+        lldb::eFormatUnsigned,
+        {LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, ax, ax},
+        value_regs, nullptr, nullptr, 0
+  };
+  info.AddSupplementaryRegister(ax_reg, group);
+
+  struct RegisterInfo al_reg {
+    "al", nullptr, 1, LLDB_INVALID_INDEX32, lldb::eEncodingUint,
+        lldb::eFormatUnsigned,
+        {LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, al, al},
+        value_regs, nullptr, nullptr, 0
+  };
+  info.AddSupplementaryRegister(al_reg, group);
+
+  info.Finalize(lldb_private::ArchSpec());
+
+  ASSERT_REG(rax, 0, {}, {eax, ax, al});
+  ASSERT_REG(eax, 0, {rax}, {rax, ax, al});
+  ASSERT_REG(ax, 0, {rax}, {rax, eax, al});
+  ASSERT_REG(al, 0, {rax}, {rax, eax, ax});
+}