Index: lld/trunk/ELF/CMakeLists.txt
===================================================================
--- lld/trunk/ELF/CMakeLists.txt
+++ lld/trunk/ELF/CMakeLists.txt
@@ -31,6 +31,7 @@
   Linker
   Object
   Option
+  Passes
   MC
   Support
   Target
Index: lld/trunk/ELF/Config.h
===================================================================
--- lld/trunk/ELF/Config.h
+++ lld/trunk/ELF/Config.h
@@ -44,6 +44,7 @@
   llvm::StringRef Emulation;
   llvm::StringRef Fini;
   llvm::StringRef Init;
+  llvm::StringRef LtoNewPmPasses;
   llvm::StringRef OutputFile;
   llvm::StringRef SoName;
   llvm::StringRef Sysroot;
Index: lld/trunk/ELF/Driver.cpp
===================================================================
--- lld/trunk/ELF/Driver.cpp
+++ lld/trunk/ELF/Driver.cpp
@@ -337,6 +337,7 @@
   Config->Entry = getString(Args, OPT_entry);
   Config->Fini = getString(Args, OPT_fini, "_fini");
   Config->Init = getString(Args, OPT_init, "_init");
+  Config->LtoNewPmPasses = getString(Args, OPT_lto_newpm_passes);
   Config->OutputFile = getString(Args, OPT_o);
   Config->SoName = getString(Args, OPT_soname);
   Config->Sysroot = getString(Args, OPT_sysroot);
@@ -495,6 +496,8 @@
   Symtab.scanVersionScript();
 
   Symtab.addCombinedLtoObject();
+  if (HasError)
+    return;
 
   for (auto *Arg : Args.filtered(OPT_wrap))
     Symtab.wrap(Arg->getValue());
Index: lld/trunk/ELF/LTO.cpp
===================================================================
--- lld/trunk/ELF/LTO.cpp
+++ lld/trunk/ELF/LTO.cpp
@@ -13,6 +13,9 @@
 #include "Error.h"
 #include "InputFiles.h"
 #include "Symbols.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CGSCCPassManager.h"
+#include "llvm/Analysis/LoopPassManager.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/ReaderWriter.h"
@@ -20,13 +23,16 @@
 #include "llvm/CodeGen/ParallelCG.h"
 #include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/PassManager.h"
 #include "llvm/Linker/IRMover.h"
+#include "llvm/Passes/PassBuilder.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
+#include <llvm/IR/Verifier.h>
 
 using namespace llvm;
 using namespace llvm::object;
@@ -56,10 +62,44 @@
   WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
 }
 
-// Run LTO passes.
-// Note that the gold plugin has a similar piece of code, so
-// it is probably better to move this code to a common place.
-static void runLTOPasses(Module &M, TargetMachine &TM) {
+static void runNewCustomLtoPasses(Module &M, TargetMachine &TM) {
+  PassBuilder PB(&TM);
+
+  AAManager AA;
+  LoopAnalysisManager LAM;
+  FunctionAnalysisManager FAM;
+  CGSCCAnalysisManager CGAM;
+  ModuleAnalysisManager MAM;
+
+  // Register the AA manager first so that our version is the one used.
+  FAM.registerPass([&] { return std::move(AA); });
+
+  // Register all the basic analyses with the managers.
+  PB.registerModuleAnalyses(MAM);
+  PB.registerCGSCCAnalyses(CGAM);
+  PB.registerFunctionAnalyses(FAM);
+  PB.registerLoopAnalyses(LAM);
+  PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
+
+  ModulePassManager MPM;
+  if (!Config->DisableVerify)
+    MPM.addPass(VerifierPass());
+
+  // Now, add all the passes we've been requested to.
+  if (!PB.parsePassPipeline(MPM, Config->LtoNewPmPasses)) {
+    error("unable to parse pass pipeline description: " +
+          Config->LtoNewPmPasses);
+    return;
+  }
+
+  if (!Config->DisableVerify)
+    MPM.addPass(VerifierPass());
+  MPM.run(M, MAM);
+}
+
+static void runOldLtoPasses(Module &M, TargetMachine &TM) {
+  // Note that the gold plugin has a similar piece of code, so
+  // it is probably better to move this code to a common place.
   legacy::PassManager LtoPasses;
   LtoPasses.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
   PassManagerBuilder PMB;
@@ -71,6 +111,21 @@
   PMB.OptLevel = Config->LtoO;
   PMB.populateLTOPassManager(LtoPasses);
   LtoPasses.run(M);
+}
+
+static void runLTOPasses(Module &M, TargetMachine &TM) {
+  if (!Config->LtoNewPmPasses.empty()) {
+    // The user explicitly asked for a set of passes to be run.
+    // This needs the new PM to work as there's no clean way to
+    // pass a set of passes to run in the legacy PM.
+    runNewCustomLtoPasses(M, TM);
+    if (HasError)
+      return;
+  } else {
+    // Run the 'default' set of LTO passes. This code still uses
+    // the legacy PM as the new one is not the default.
+    runOldLtoPasses(M, TM);
+  }
 
   if (Config->SaveTemps)
     saveBCFile(M, ".lto.opt.bc");
@@ -226,6 +281,8 @@
 
   std::unique_ptr<TargetMachine> TM = CreateTargetMachine();
   runLTOPasses(*Combined, *TM);
+  if (HasError)
+    return {};
 
   return runSplitCodegen(CreateTargetMachine);
 }
Index: lld/trunk/ELF/Options.td
===================================================================
--- lld/trunk/ELF/Options.td
+++ lld/trunk/ELF/Options.td
@@ -255,6 +255,8 @@
 // LTO-related options.
 def lto_jobs : Joined<["--"], "lto-jobs=">,
   HelpText<"Number of threads to run codegen">;
+def lto_newpm_passes : Joined<["--"], "lto-newpm-passes=">,
+  HelpText<"Passes to run during LTO">;
 def disable_verify : Flag<["-"], "disable-verify">;
 def mllvm : Separate<["-"], "mllvm">;
 def save_temps : Flag<["-"], "save-temps">;
Index: lld/trunk/test/ELF/lto/ltopasses-custom.ll
===================================================================
--- lld/trunk/test/ELF/lto/ltopasses-custom.ll
+++ lld/trunk/test/ELF/lto/ltopasses-custom.ll
@@ -0,0 +1,29 @@
+; REQUIRES: x86
+; RUN: llvm-as %s -o %t.o
+; RUN: ld.lld -m elf_x86_64 %t.o -o %t.so -save-temps --lto-newpm-passes=ipsccp -shared
+; RUN: ld.lld -m elf_x86_64 %t.o -o %t2.so -save-temps --lto-newpm-passes=loweratomic -shared
+; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t2.so.lto.opt.bc -o - | FileCheck %s --check-prefix=ATOMIC
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @barrier() {
+  fence seq_cst
+  ret void
+}
+
+; IPSCCP won't remove the fence.
+; CHECK: define void @barrier() {
+; CHECK-NEXT: fence seq_cst
+; CHECK-NEXT: ret void
+
+; LowerAtomic will remove the fence.
+; ATOMIC: define void @barrier() {
+; ATOMIC-NEXT: ret void
+
+; Check that invalid passes are rejected gracefully.
+; RUN: not ld.lld -m elf_x86_64 %t.o -o %t2.so \
+; RUN:   --lto-newpm-passes=iamnotapass -shared 2>&1 | \
+; RUN:   FileCheck %s --check-prefix=INVALID
+; INVALID: unable to parse pass pipeline description: iamnotapass