diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -267,6 +267,10 @@
   directory (``/tmp`` on \*NIX systems, if none of the environment variables
   TMPDIR, TMP, and TEMP are specified).
 
+- ``-ffat-lto-objects`` can now be used to emit object files with both object
+  code and LLVM bitcode. Previously this flag was ignored for GCC compatibility.
+  (`See patch <https://reviews.llvm.org/D146777>`_).
+
 Removed Compiler Flags
 -------------------------
 - The deprecated flag `-fmodules-ts` is removed. Please use ``-std=c++20``
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -164,6 +164,7 @@
                                      ///< compile step.
 CODEGENOPT(LTOUnit, 1, 0) ///< Emit IR to support LTO unit features (CFI, whole
                           ///< program vtable opt).
+CODEGENOPT(FatLTO, 1, 0) ///< Set when -ffat-lto-objects is enabled.
 CODEGENOPT(EnableSplitLTOUnit, 1, 0) ///< Enable LTO unit splitting to support
 				     /// CFI and traditional whole program
 				     /// devirtualization that require whole
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2366,6 +2366,11 @@
   Flags<[CoreOption, CC1Option]>, Group<f_Group>,
   HelpText<"Write minimized bitcode to <file> for the ThinLTO thin link only">,
   MarshallingInfoString<CodeGenOpts<"ThinLinkBitcodeFile">>;
+defm fat_lto_objects : BoolFOption<"fat-lto-objects",
+  CodeGenOpts<"FatLTO">, DefaultFalse,
+  PosFlag<SetTrue, [CC1Option], "Enable">,
+  NegFlag<SetFalse, [CC1Option], "Disable">,
+  BothFlags<[CC1Option], " fat LTO object support">>;
 def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,
   Group<f_Group>, Flags<[NoXarchOption, CC1Option, CoreOption]>,
   HelpText<"Set the maximum number of entries to print in a macro expansion backtrace (0 = no limit)">,
@@ -5136,7 +5141,6 @@
 defm reorder_blocks : BooleanFFlag<"reorder-blocks">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm default_inline : BooleanFFlag<"default-inline">, Group<clang_ignored_gcc_optimization_f_Group>;
-defm fat_lto_objects : BooleanFFlag<"fat-lto-objects">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm float_store : BooleanFFlag<"float-store">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm friend_injection : BooleanFFlag<"friend-injection">, Group<clang_ignored_f_Group>;
 defm function_attribute_list : BooleanFFlag<"function-attribute-list">, Group<clang_ignored_f_Group>;
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -55,6 +55,7 @@
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/TargetParser/SubtargetFeature.h"
 #include "llvm/TargetParser/Triple.h"
+#include "llvm/Transforms/IPO/EmbedBitcodePass.h"
 #include "llvm/Transforms/IPO/LowerTypeTests.h"
 #include "llvm/Transforms/IPO/ThinLTOBitcodeWriter.h"
 #include "llvm/Transforms/InstCombine/InstCombine.h"
@@ -1015,7 +1016,12 @@
           });
     }
 
-    if (IsThinLTO || (IsLTO && CodeGenOpts.UnifiedLTO)) {
+    bool IsThinOrUnifiedLTO = IsThinLTO || (IsLTO && CodeGenOpts.UnifiedLTO);
+    if (CodeGenOpts.FatLTO) {
+      MPM = PB.buildFatLTODefaultPipeline(Level, IsThinOrUnifiedLTO,
+                                          IsThinOrUnifiedLTO ||
+                                              shouldEmitRegularLTOSummary());
+    } else if (IsThinOrUnifiedLTO) {
       MPM = PB.buildThinLTOPreLinkDefaultPipeline(Level);
     } else if (IsLTO) {
       MPM = PB.buildLTOPreLinkDefaultPipeline(Level);
@@ -1071,6 +1077,21 @@
                                     EmitLTOSummary));
     }
   }
+  if (CodeGenOpts.FatLTO) {
+    // Set module flags, like EnableSplitLTOUnit and UnifiedLTO, since FatLTO
+    // uses a different action than Backend_EmitBC or Backend_EmitLL.
+    bool IsThinOrUnifiedLTO =
+        CodeGenOpts.PrepareForThinLTO ||
+        (CodeGenOpts.PrepareForLTO && CodeGenOpts.UnifiedLTO);
+    if (!TheModule->getModuleFlag("ThinLTO"))
+      TheModule->addModuleFlag(Module::Error, "ThinLTO",
+                               uint32_t(IsThinOrUnifiedLTO));
+    if (!TheModule->getModuleFlag("EnableSplitLTOUnit"))
+      TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
+                               uint32_t(CodeGenOpts.EnableSplitLTOUnit));
+    if (CodeGenOpts.UnifiedLTO && !TheModule->getModuleFlag("UnifiedLTO"))
+      TheModule->addModuleFlag(Module::Error, "UnifiedLTO", uint32_t(1));
+  }
 
   // Now that we have all of the passes ready, run them.
   {
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -4729,8 +4729,13 @@
   }
   case phases::Backend: {
     if (isUsingLTO() && TargetDeviceOffloadKind == Action::OFK_None) {
-      types::ID Output =
-          Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
+      types::ID Output;
+      if (Args.hasArg(options::OPT_S))
+        Output = types::TY_LTO_IR;
+      else if (Args.hasArg(options::OPT_ffat_lto_objects))
+        Output = types::TY_PP_Asm;
+      else
+        Output = types::TY_LTO_BC;
       return C.MakeAction<BackendJobAction>(Input, Output);
     }
     if (isUsingLTO(/* IsOffload */ true) &&
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7354,6 +7354,22 @@
   if (SplitLTOUnit)
     CmdArgs.push_back("-fsplit-lto-unit");
 
+  if (Arg *A = Args.getLastArg(options::OPT_ffat_lto_objects,
+                               options::OPT_fno_fat_lto_objects)) {
+    if (IsUsingLTO && A->getOption().matches(options::OPT_ffat_lto_objects)) {
+      assert(LTOMode == LTOK_Full || LTOMode == LTOK_Thin);
+      if (!Triple.isOSBinFormatELF()) {
+        D.Diag(diag::err_drv_unsupported_opt_for_target)
+            << A->getAsString(Args) << TC.getTripleString();
+      }
+      CmdArgs.push_back(Args.MakeArgString(
+          Twine("-flto=") + (LTOMode == LTOK_Thin ? "thin" : "full")));
+      CmdArgs.push_back("-flto-unit");
+      CmdArgs.push_back("-ffat-lto-objects");
+      A->render(Args, CmdArgs);
+    }
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_fglobal_isel,
                                options::OPT_fno_global_isel)) {
     CmdArgs.push_back("-mllvm");
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -617,6 +617,11 @@
                                 PluginName + Suffix,
                             Plugin);
     CmdArgs.push_back(Args.MakeArgString(Twine(PluginPrefix) + Plugin));
+  } else {
+    // Tell LLD to find and use .llvm.lto section in regular relocatable object
+    // files
+    if (Args.hasArg(options::OPT_ffat_lto_objects))
+      CmdArgs.push_back("--fat-lto-objects");
   }
 
   const char *PluginOptPrefix = IsOSAIX ? "-bplugin_opt:" : "-plugin-opt=";
diff --git a/clang/test/CodeGen/fat-lto-objects.c b/clang/test/CodeGen/fat-lto-objects.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/fat-lto-objects.c
@@ -0,0 +1,57 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -fsplit-lto-unit -emit-llvm < %s  | FileCheck %s --check-prefixes=FULL,SPLIT
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -emit-llvm < %s  | FileCheck %s --check-prefixes=FULL,SPLIT
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -fsplit-lto-unit -ffat-lto-objects -emit-llvm < %s  | FileCheck %s --check-prefixes=THIN,SPLIT
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -ffat-lto-objects -emit-llvm < %s  | FileCheck %s --check-prefixes=THIN,NOSPLIT
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -fsplit-lto-unit -emit-obj < %s -o %t.full.split.o
+// RUN: llvm-readelf -S %t.full.split.o | FileCheck %s --check-prefixes=ELF
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.full.split.bc %t.full.split.o
+// RUN: llvm-dis %t.full.split.bc -o - | FileCheck %s --check-prefixes=FULL,SPLIT,NOUNIFIED
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -emit-obj < %s -o %t.full.nosplit.o
+// RUN: llvm-readelf -S %t.full.nosplit.o | FileCheck %s --check-prefixes=ELF
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.full.nosplit.bc %t.full.nosplit.o
+// RUN: llvm-dis %t.full.nosplit.bc -o - | FileCheck %s --check-prefixes=FULL,NOSPLIT,NOUNIFIED
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -fsplit-lto-unit -ffat-lto-objects -emit-obj < %s -o %t.thin.split.o
+// RUN: llvm-readelf -S %t.thin.split.o | FileCheck %s --check-prefixes=ELF
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.thin.split.bc %t.thin.split.o
+// RUN: llvm-dis %t.thin.split.bc -o - | FileCheck %s --check-prefixes=THIN,SPLIT,NOUNIFIED
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -ffat-lto-objects -emit-obj < %s -o %t.thin.nosplit.o
+// RUN: llvm-readelf -S %t.thin.nosplit.o | FileCheck %s --check-prefixes=ELF
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.thin.nosplit.bc %t.thin.nosplit.o
+// RUN: llvm-dis %t.thin.nosplit.bc -o -  | FileCheck %s --check-prefixes=THIN,NOSPLIT,NOUNIFIED
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=thin -funified-lto -ffat-lto-objects -emit-obj < %s -o %t.unified.o
+// RUN: llvm-readelf -S %t.unified.o | FileCheck %s --check-prefixes=ELF
+// RUN: llvm-objcopy --dump-section=.llvm.lto=%t.unified.bc %t.unified.o
+// RUN: llvm-dis %t.unified.bc -o - | FileCheck %s --check-prefixes=THIN,NOSPLIT,UNIFIED
+
+// RUN: %clang -cc1 -triple x86_64-unknown-linux-gnu -flto=full -ffat-lto-objects -fsplit-lto-unit -S < %s -o - \
+// RUN: | FileCheck %s --check-prefixes=ASM
+
+/// Check that the ThinLTO metadata is only set false for full LTO.
+// FULL: ![[#]] = !{i32 1, !"ThinLTO", i32 0}
+// THIN-NOT: ![[#]] = !{i32 1, !"ThinLTO", i32 0}
+
+/// Be sure we enable split LTO units correctly under -ffat-lto-objects.
+// SPLIT: ![[#]] = !{i32 1, !"EnableSplitLTOUnit", i32 1}
+// NOSPLIT: ![[#]] = !{i32 1, !"EnableSplitLTOUnit", i32 0}
+
+// UNIFIED: ![[#]] = !{i32 1, !"UnifiedLTO", i32 1}
+// NOUNIFIED-NOT: ![[#]] = !{i32 1, !"UnifiedLTO", i32 1}
+
+// ELF: .llvm.lto
+
+//      ASM: .section        .llvm.lto,"e",@progbits
+// ASM-NEXT: .Lllvm.embedded.object:
+// ASM-NEXT:        .asciz  "BC
+// ASM-NEXT: .size   .Lllvm.embedded.object
+
+int test(void) {
+  return 0xabcd;
+}
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -424,7 +424,6 @@
 // CHECK-WARNING-DAG: optimization flag '-fwhole-program' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fcaller-saves' is not supported
 // CHECK-WARNING-DAG: optimization flag '-freorder-blocks' is not supported
-// CHECK-WARNING-DAG: optimization flag '-ffat-lto-objects' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fmerge-constants' is not supported
 // CHECK-WARNING-DAG: optimization flag '-finline-small-functions' is not supported
 // CHECK-WARNING-DAG: optimization flag '-ftree-dce' is not supported
diff --git a/clang/test/Driver/fat-lto-objects.c b/clang/test/Driver/fat-lto-objects.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/fat-lto-objects.c
@@ -0,0 +1,34 @@
+// RUN: %clang --target=x86_64-unknown-linux-gnu -flto -ffat-lto-objects -### %s -c 2>&1 | FileCheck %s -check-prefix=CHECK-CC
+// CHECK-CC: -cc1
+// CHECK-CC-SAME: -emit-obj
+// CHECK-CC-SAME: -ffat-lto-objects
+
+/// Without -flto -S will just emit normal ASM, so we don't expect -emit-{llvm,obj} or -ffat-lto-objects to be passed to cc1.
+// RUN: %clang --target=x86_64-unknown-linux-gnu -ffat-lto-objects -### %s -S 2>&1 | FileCheck %s -check-prefix=CHECK-CC-S
+// CHECK-CC-S: -cc1
+// CHECK-CC-S: -S
+// CHECK-CC-S-NOT: -emit-obj
+// CHECK-CC-S-NOT: -emit-llvm
+// CHECK-CC-S-NOT: -ffat-lto-objects
+
+/// When LTO is enabled, we expect LLVM IR output and -ffat-lto-objects to be passed to cc1.
+// RUN: %clang --target=x86_64-unknown-linux-gnu -flto -ffat-lto-objects -### %s -S 2>&1 | FileCheck %s -check-prefix=CHECK-CC-S-LTO
+// RUN: %clang --target=x86_64-unknown-linux-gnu -flto -ffat-lto-objects -### %s -S -emit-llvm 2>&1 | FileCheck %s -check-prefix=CHECK-CC-S-LTO
+// CHECK-CC-S-LTO: -cc1
+// CHECK-CC-S-LTO-SAME: -emit-llvm
+// CHECK-CC-S-LTO-SAME: -ffat-lto-objects
+
+/// Make sure we don't have a warning for -ffat-lto-objects being unused
+// RUN: %clang --target=x86_64-unknown-linux-gnu -ffat-lto-objects -fdriver-only -Werror -v %s -c 2>&1 | FileCheck %s -check-prefix=CHECK-CC-NOLTO
+// CHECK-CC-NOLTO: -cc1
+// CHECK-CC-NOLTO-SAME: -emit-obj
+// CHECK-CC-NOLTO-NOT: -ffat-lto-objects
+
+/// We need to pass an additional flag (--fat-lto-objects) to lld when linking w/ -flto -ffat-lto-objects
+/// But it should not be there when LTO is disabled w/ -fno-lto
+// RUN: %clang --target=x86_64-unknown-linux-gnu --sysroot=%S/Inputs/basic_cross_linux_tree %s \
+// RUN:   -fuse-ld=lld -flto -ffat-lto-objects -### 2>&1 | FileCheck --check-prefix=LTO %s
+// RUN: %clang --target=x86_64-unknown-linux-gnu --sysroot=%S/Inputs/basic_cross_linux_tree %s \
+// RUN:   -fuse-ld=lld -fno-lto -ffat-lto-objects -### 2>&1 | FileCheck --check-prefix=NOLTO %s
+// LTO: "--fat-lto-objects"
+// NOLTO-NOT: "--fat-lto-objects"