Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -16,6 +16,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/BinaryFormat/ELF.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/Support/CachePruning.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Endian.h"
@@ -358,6 +359,8 @@
   // this means to map the primary and thread stacks as PROT_MTE. Note: This is
   // not supported on Android 11 & 12.
   bool androidMemtagStack;
+  // When using a unified pre-link LTO pipeline, specify the backend LTO mode.
+  llvm::lto::LTO::LTOKind forceLTOMode = llvm::lto::LTO::LTOK_Default;
 };
 
 // The only instance of Configuration struct.
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -1317,6 +1317,19 @@
   for (auto *arg : args.filtered(OPT_mllvm))
     parseClangOption(arg->getValue(), arg->getSpelling());
 
+  config->forceLTOMode = llvm::lto::LTO::LTOK_Default;
+  if (auto *arg = args.getLastArg(OPT_lto_type_eq)) {
+    StringRef s = arg->getValue();
+    if (s == "thin")
+      config->forceLTOMode = llvm::lto::LTO::LTOK_UnifiedThin;
+    else if (s == "full")
+      config->forceLTOMode = llvm::lto::LTO::LTOK_UnifiedRegular;
+    else if (s == "default")
+      config->forceLTOMode = llvm::lto::LTO::LTOK_Default;
+    else
+      error("unknown LTO mode: " + s);
+  }
+
   // --threads= takes a positive integer and provides the default value for
   // --thinlto-jobs=.
   if (auto *arg = args.getLastArg(OPT_threads)) {
Index: lld/ELF/LTO.cpp
===================================================================
--- lld/ELF/LTO.cpp
+++ lld/ELF/LTO.cpp
@@ -201,7 +201,8 @@
   }
 
   ltoObj = std::make_unique<lto::LTO>(createConfig(), backend,
-                                       config->ltoPartitions);
+                                      config->ltoPartitions,
+                                      config->forceLTOMode);
 
   // Initialize usedStartStop.
   if (bitcodeFiles.empty())
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -541,6 +541,9 @@
 def: Flag<["-"], "V">, Alias<version>, HelpText<"Alias for --version">;
 
 // LTO-related options.
+
+def lto_type_eq: J<"lto=">, HelpText<"Set LTO backend">,
+                 MetaVarName<"[full,thin]">;
 def lto_aa_pipeline: JJ<"lto-aa-pipeline=">,
   HelpText<"AA pipeline to run during LTO. Used in conjunction with -lto-newpm-passes">;
 def lto_debug_pass_manager: FF<"lto-debug-pass-manager">,