Index: include/clang/Basic/CodeGenOptions.h
===================================================================
--- include/clang/Basic/CodeGenOptions.h
+++ include/clang/Basic/CodeGenOptions.h
@@ -70,8 +70,6 @@
     LocalExecTLSModel
   };
 
-  enum DwarfFissionKind { NoFission, SplitFileFission, SingleFileFission };
-
   /// Clang versions with different platform ABI conformance.
   enum class ClangABI {
     /// Attempt to be ABI-compatible with code generated by Clang 3.8.x
@@ -184,10 +182,12 @@
   /// file, for example with -save-temps.
   std::string MainFileName;
 
-  /// The name for the split debug info file that we'll break out. This is used
-  /// in the backend for setting the name in the skeleton cu.
+  /// The name for the split debug info file used in the skeleton CU.
   std::string SplitDwarfFile;
 
+  /// Output filename for the split debug info, not used in the skeleton CU.
+  std::string SplitDwarfOutput;
+
   /// The name of the relocation model to use.
   llvm::Reloc::Model RelocationModel;
 
Index: include/clang/Basic/CodeGenOptions.def
===================================================================
--- include/clang/Basic/CodeGenOptions.def
+++ include/clang/Basic/CodeGenOptions.def
@@ -260,7 +260,7 @@
                                        ///< contain explicit imports for
                                        ///< anonymous namespaces
 
-ENUM_CODEGENOPT(SplitDwarfMode, DwarfFissionKind, 2, NoFission) ///< DWARF fission mode to use.
+CODEGENOPT(EnableSplitDwarf, 1, 0) ///< Whether to enable split DWARF.
 
 CODEGENOPT(SplitDwarfInlining, 1, 1) ///< Whether to include inlining info in the
                                      ///< skeleton CU to allow for symbolication
Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -650,7 +650,7 @@
   HelpText<"Print the compiler version">;
 def main_file_name : Separate<["-"], "main-file-name">,
   HelpText<"Main file name to use for debug info">;
-def split_dwarf_file : Separate<["-"], "split-dwarf-file">,
+def split_dwarf_output : Separate<["-"], "split-dwarf-output">,
   HelpText<"File name to use for split dwarf debug info output">;
 
 }
@@ -661,8 +661,8 @@
   HelpText<"Assume all functions with C linkage do not unwind">;
 def enable_split_dwarf : Flag<["-"], "enable-split-dwarf">,
   HelpText<"Use DWARF fission in 'split' mode">;
-def enable_split_dwarf_EQ : Joined<["-"], "enable-split-dwarf=">,
-  HelpText<"Set DWARF fission mode to either 'split' or 'single'">, Values<"split,single">;
+def split_dwarf_file : Separate<["-"], "split-dwarf-file">,
+  HelpText<"File name for the split debug info to encode in the DWARF output">;
 def fno_wchar : Flag<["-"], "fno-wchar">,
   HelpText<"Disable C++ builtin type wchar_t">;
 def fconstant_string_class : Separate<["-"], "fconstant-string-class">,
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -464,7 +464,7 @@
   Options.EmitStackSizeSection = CodeGenOpts.StackSizeSection;
   Options.EmitAddrsig = CodeGenOpts.Addrsig;
 
-  if (CodeGenOpts.getSplitDwarfMode() != CodeGenOptions::NoFission)
+  if (CodeGenOpts.EnableSplitDwarf)
     Options.MCOptions.SplitDwarfFile = CodeGenOpts.SplitDwarfFile;
   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
@@ -844,9 +844,8 @@
     break;
 
   default:
-    if (!CodeGenOpts.SplitDwarfFile.empty() &&
-        (CodeGenOpts.getSplitDwarfMode() == CodeGenOptions::SplitFileFission)) {
-      DwoOS = openOutputFile(CodeGenOpts.SplitDwarfFile);
+    if (CodeGenOpts.EnableSplitDwarf && !CodeGenOpts.SplitDwarfOutput.empty()) {
+      DwoOS = openOutputFile(CodeGenOpts.SplitDwarfOutput);
       if (!DwoOS)
         return;
     }
@@ -1192,8 +1191,8 @@
     NeedCodeGen = true;
     CodeGenPasses.add(
         createTargetTransformInfoWrapperPass(getTargetIRAnalysis()));
-    if (!CodeGenOpts.SplitDwarfFile.empty()) {
-      DwoOS = openOutputFile(CodeGenOpts.SplitDwarfFile);
+    if (!CodeGenOpts.SplitDwarfOutput.empty()) {
+      DwoOS = openOutputFile(CodeGenOpts.SplitDwarfOutput);
       if (!DwoOS)
         return;
     }
@@ -1343,7 +1342,7 @@
   Conf.RemarksWithHotness = CGOpts.DiagnosticsWithHotness;
   Conf.RemarksFilename = CGOpts.OptRecordFile;
   Conf.RemarksPasses = CGOpts.OptRecordPasses;
-  Conf.DwoPath = CGOpts.SplitDwarfFile;
+  Conf.DwoPath = CGOpts.SplitDwarfOutput;
   switch (Action) {
   case Backend_EmitNothing:
     Conf.PreCodeGenModuleHook = [](size_t Task, const Module &Mod) {
Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -610,9 +610,7 @@
       LangTag, CUFile, CGOpts.EmitVersionIdentMetadata ? Producer : "",
       LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers,
-      (CGOpts.getSplitDwarfMode() != CodeGenOptions::NoFission)
-          ? ""
-          : CGOpts.SplitDwarfFile,
+      CGOpts.EnableSplitDwarf ? "" : CGOpts.SplitDwarfFile,
       EmissionKind, DwoId, CGOpts.SplitDwarfInlining,
       CGOpts.DebugInfoForProfiling,
       CGM.getTarget().getTriple().isNVPTX()
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3282,11 +3282,7 @@
     if (DwarfFission != DwarfFissionKind::None) {
       if (DebugInfoKind == codegenoptions::NoDebugInfo)
         DebugInfoKind = codegenoptions::LimitedDebugInfo;
-
-      if (DwarfFission == DwarfFissionKind::Single)
-        CmdArgs.push_back("-enable-split-dwarf=single");
-      else
-        CmdArgs.push_back("-enable-split-dwarf");
+      CmdArgs.push_back("-enable-split-dwarf");
     }
   }
 
@@ -4092,11 +4088,14 @@
                     TC.getTriple().isOSBinFormatELF() &&
                     (isa<AssembleJobAction>(JA) || isa<CompileJobAction>(JA) ||
                      isa<BackendJobAction>(JA));
-  const char *SplitDWARFOut;
   if (SplitDWARF) {
+    const char* SplitDWARFOut = SplitDebugName(Args, Input, Output);
     CmdArgs.push_back("-split-dwarf-file");
-    SplitDWARFOut = SplitDebugName(Args, Input, Output);
     CmdArgs.push_back(SplitDWARFOut);
+    if (DwarfFission == DwarfFissionKind::Split) {
+      CmdArgs.push_back("-split-dwarf-output");
+      CmdArgs.push_back(SplitDWARFOut);
+    }
   }
 
   // Pass the linker version in use.
@@ -6154,7 +6153,7 @@
   Arg *A;
   if (getDebugFissionKind(D, Args, A) == DwarfFissionKind::Split &&
       T.isOSBinFormatELF()) {
-    CmdArgs.push_back("-split-dwarf-file");
+    CmdArgs.push_back("-split-dwarf-output");
     CmdArgs.push_back(SplitDebugName(Args, Input, Output));
   }
 
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -713,25 +713,10 @@
   Opts.MacroDebugInfo = Args.hasArg(OPT_debug_info_macro);
   Opts.WholeProgramVTables = Args.hasArg(OPT_fwhole_program_vtables);
   Opts.LTOVisibilityPublicStd = Args.hasArg(OPT_flto_visibility_public_std);
+  Opts.EnableSplitDwarf = Args.hasArg(OPT_enable_split_dwarf);
   Opts.SplitDwarfFile = Args.getLastArgValue(OPT_split_dwarf_file);
+  Opts.SplitDwarfOutput = Args.getLastArgValue(OPT_split_dwarf_output);
   Opts.SplitDwarfInlining = !Args.hasArg(OPT_fno_split_dwarf_inlining);
-
-  if (Arg *A =
-          Args.getLastArg(OPT_enable_split_dwarf, OPT_enable_split_dwarf_EQ)) {
-    if (A->getOption().matches(options::OPT_enable_split_dwarf)) {
-      Opts.setSplitDwarfMode(CodeGenOptions::SplitFileFission);
-    } else {
-      StringRef Name = A->getValue();
-      if (Name == "single")
-        Opts.setSplitDwarfMode(CodeGenOptions::SingleFileFission);
-      else if (Name == "split")
-        Opts.setSplitDwarfMode(CodeGenOptions::SplitFileFission);
-      else
-        Diags.Report(diag::err_drv_invalid_value)
-            << A->getAsString(Args) << Name;
-    }
-  }
-
   Opts.DebugTypeExtRefs = Args.hasArg(OPT_dwarf_ext_refs);
   Opts.DebugExplicitImport = Args.hasArg(OPT_dwarf_explicit_import);
   Opts.DebugFwdTemplateParams = Args.hasArg(OPT_debug_forward_template_params);
Index: test/CodeGen/split-debug-filename.c
===================================================================
--- test/CodeGen/split-debug-filename.c
+++ test/CodeGen/split-debug-filename.c
@@ -1,7 +1,7 @@
 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 -debug-info-kind=limited -split-dwarf-file foo.dwo -S -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -debug-info-kind=limited -enable-split-dwarf -split-dwarf-file foo.dwo -S -emit-llvm -o - %s | FileCheck --check-prefix=VANILLA %s
-// RUN: %clang_cc1 -triple x86_64-unknown-linux -debug-info-kind=limited -enable-split-dwarf -split-dwarf-file %t.dwo -emit-obj -o - %s | llvm-objdump -section-headers - | FileCheck --check-prefix=O %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -debug-info-kind=limited -enable-split-dwarf -split-dwarf-file %t.dwo -split-dwarf-output %t.dwo -emit-obj -o - %s | llvm-objdump -section-headers - | FileCheck --check-prefix=O %s
 // RUN: llvm-objdump -section-headers %t.dwo | FileCheck --check-prefix=DWO %s
 
 int main (void) {
Index: test/CodeGen/split-debug-output.c
===================================================================
--- /dev/null
+++ test/CodeGen/split-debug-output.c
@@ -0,0 +1,7 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -debug-info-kind=limited -enable-split-dwarf -split-dwarf-file foo.dwo -split-dwarf-output %t -emit-obj -o - %s | llvm-dwarfdump -debug-info - | FileCheck %s
+// RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+
+int f() { return 0; }
+
+// CHECK: DW_AT_GNU_dwo_name ("foo.dwo")
Index: test/CodeGen/split-debug-single-file.c
===================================================================
--- test/CodeGen/split-debug-single-file.c
+++ test/CodeGen/split-debug-single-file.c
@@ -1,14 +1,15 @@
 // REQUIRES: x86-registered-target
 
-// Testing to ensure -enable-split-dwarf=single allows to place .dwo sections into regular output object.
+// Testing to ensure that setting only -split-dwarf-file allows to place .dwo sections into regular output object.
 //  RUN: %clang_cc1 -debug-info-kind=limited -triple x86_64-unknown-linux \
-//  RUN:   -enable-split-dwarf=single -split-dwarf-file %t.o -emit-obj -o %t.o %s
+//  RUN:   -enable-split-dwarf -split-dwarf-file %t.dwo -emit-obj -o %t.o %s
 //  RUN: llvm-objdump -section-headers %t.o | FileCheck --check-prefix=MODE-SINGLE %s
 //  MODE-SINGLE: .dwo
 
-// Testing to ensure -enable-split-dwarf=split does not place .dwo sections into regular output object.
+// Testing to ensure that setting both -split-dwarf-file and -split-dwarf-output
+// does not place .dwo sections into regular output object.
 //  RUN: %clang_cc1 -debug-info-kind=limited -triple x86_64-unknown-linux \
-//  RUN:   -enable-split-dwarf=split -split-dwarf-file %t.o -emit-obj -o %t.o %s
+//  RUN:   -enable-split-dwarf -split-dwarf-file %t.dwo -split-dwarf-output %t.dwo -emit-obj -o %t.o %s
 //  RUN: llvm-objdump -section-headers %t.o | FileCheck --check-prefix=MODE-SPLIT %s
 //  MODE-SPLIT-NOT: .dwo
 
Index: test/Driver/split-debug.c
===================================================================
--- test/Driver/split-debug.c
+++ test/Driver/split-debug.c
@@ -3,7 +3,7 @@
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-ACTIONS < %t %s
 //
-// CHECK-ACTIONS: "-split-dwarf-file" "split-debug.dwo"
+// CHECK-ACTIONS: "-split-dwarf-file" "split-debug.dwo" "-split-dwarf-output" "split-debug.dwo"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-ACTIONS < %t %s
@@ -13,13 +13,15 @@
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf=single -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-ACTIONS-SINGLE-SPLIT < %t %s
 //
-// CHECK-ACTIONS-SINGLE-SPLIT: "-enable-split-dwarf=single"
+// CHECK-ACTIONS-SINGLE-SPLIT: "-enable-split-dwarf"
 // CHECK-ACTIONS-SINGLE-SPLIT: "-split-dwarf-file" "split-debug.o"
+// CHECK-ACTIONS-SINGLE-SPLIT-NOT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf=single -c -### -o %tfoo.o %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-SINGLE-SPLIT-FILENAME < %t %s
 //
 // CHECK-SINGLE-SPLIT-FILENAME: "-split-dwarf-file" "{{.*}}foo.o"
+// CHECK-SINGLE-SPLIT-FILENAME-NOT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-macosx -gsplit-dwarf -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-NO-ACTIONS < %t %s
@@ -41,7 +43,7 @@
 // RUN: %clang -target amdgcn-amd-amdhsa -gsplit-dwarf -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-OPTION < %t %s
 //
-// CHECK-OPTION: "-split-dwarf-file" "split-debug.dwo"
+// CHECK-OPTION: "-split-dwarf-file" "split-debug.dwo" "-split-dwarf-output" "split-debug.dwo"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-ASM < %t %s
@@ -59,6 +61,7 @@
 // CHECK-GMLT-WITH-SPLIT: "-enable-split-dwarf"
 // CHECK-GMLT-WITH-SPLIT: "-debug-info-kind=line-tables-only"
 // CHECK-GMLT-WITH-SPLIT: "-split-dwarf-file"
+// CHECK-GMLT-WITH-SPLIT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -g -fno-split-dwarf-inlining -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-NOINLINE-WITHOUT-SPLIT < %t %s
@@ -87,12 +90,14 @@
 // CHECK-GMLT-OVER-SPLIT-NOT: "-enable-split-dwarf"
 // CHECK-GMLT-OVER-SPLIT: "-debug-info-kind=line-tables-only"
 // CHECK-GMLT-OVER-SPLIT-NOT: "-split-dwarf-file"
+// CHECK-GMLT-OVER-SPLIT-NOT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gmlt -gsplit-dwarf -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-SPLIT-OVER-GMLT < %t %s
 //
 // CHECK-SPLIT-OVER-GMLT: "-enable-split-dwarf" "-debug-info-kind=limited"
 // CHECK-SPLIT-OVER-GMLT: "-split-dwarf-file"
+// CHECK-SPLIT-OVER-GMLT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -g0 -fno-split-dwarf-inlining -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-G0-OVER-SPLIT < %t %s
@@ -100,6 +105,7 @@
 // CHECK-G0-OVER-SPLIT-NOT: "-enable-split-dwarf"
 // CHECK-G0-OVER-SPLIT-NOT: "-debug-info-kind
 // CHECK-G0-OVER-SPLIT-NOT: "-split-dwarf-file"
+// CHECK-G0-OVER-SPLIT-NOT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -g0 -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-G0-OVER-SPLIT < %t %s
@@ -107,9 +113,11 @@
 // CHECK-G0-OVER-SPLIT-NOT: "-enable-split-dwarf"
 // CHECK-G0-OVER-SPLIT-NOT: "-debug-info-kind
 // CHECK-G0-OVER-SPLIT-NOT: "-split-dwarf-file"
+// CHECK-G0-OVER-SPLIT-NOT: "-split-dwarf-output"
 
 // RUN: %clang -target x86_64-unknown-linux-gnu -g0 -gsplit-dwarf -S -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-SPLIT-OVER-G0 < %t %s
 //
 // CHECK-SPLIT-OVER-G0: "-enable-split-dwarf" "-debug-info-kind=limited"
 // CHECK-SPLIT-OVER-G0: "-split-dwarf-file"
+// CHECK-SPLIT-OVER-G0: "-split-dwarf-output"
Index: test/Driver/split-debug.s
===================================================================
--- test/Driver/split-debug.s
+++ test/Driver/split-debug.s
@@ -3,7 +3,7 @@
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf -c -### %s 2> %t
 // RUN: FileCheck -check-prefix=CHECK-ACTIONS < %t %s
 //
-// CHECK-ACTIONS: "-split-dwarf-file" "split-debug.dwo"
+// CHECK-ACTIONS: "-split-dwarf-output" "split-debug.dwo"
 
 // Check we pass -split-dwarf-file to `as` if -gsplit-dwarf=split.
 // RUN: %clang -target x86_64-unknown-linux-gnu -gsplit-dwarf=split -c -### %s 2> %t
Index: test/Misc/cc1as-split-dwarf.s
===================================================================
--- test/Misc/cc1as-split-dwarf.s
+++ test/Misc/cc1as-split-dwarf.s
@@ -1,5 +1,5 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang -cc1as -triple x86_64-pc-linux-gnu %s -filetype obj -o %t1 -split-dwarf-file %t2
+// RUN: %clang -cc1as -triple x86_64-pc-linux-gnu %s -filetype obj -o %t1 -split-dwarf-output %t2
 // RUN: llvm-objdump -s %t1 | FileCheck --check-prefix=O %s
 // RUN: llvm-objdump -s %t2 | FileCheck --check-prefix=DWO %s
 
Index: tools/driver/cc1as_main.cpp
===================================================================
--- tools/driver/cc1as_main.cpp
+++ tools/driver/cc1as_main.cpp
@@ -98,7 +98,7 @@
   llvm::DebugCompressionType CompressDebugSections =
       llvm::DebugCompressionType::None;
   std::string MainFileName;
-  std::string SplitDwarfFile;
+  std::string SplitDwarfOutput;
 
   /// @}
   /// @name Frontend Options
@@ -258,7 +258,7 @@
   }
   Opts.LLVMArgs = Args.getAllArgValues(OPT_mllvm);
   Opts.OutputPath = Args.getLastArgValue(OPT_o);
-  Opts.SplitDwarfFile = Args.getLastArgValue(OPT_split_dwarf_file);
+  Opts.SplitDwarfOutput = Args.getLastArgValue(OPT_split_dwarf_output);
   if (Arg *A = Args.getLastArg(OPT_filetype)) {
     StringRef Name = A->getValue();
     unsigned OutputType = StringSwitch<unsigned>(Name)
@@ -367,8 +367,8 @@
   if (!FDOS)
     return true;
   std::unique_ptr<raw_fd_ostream> DwoOS;
-  if (!Opts.SplitDwarfFile.empty())
-    DwoOS = getOutputStream(Opts.SplitDwarfFile, Diags, IsBinary);
+  if (!Opts.SplitDwarfOutput.empty())
+    DwoOS = getOutputStream(Opts.SplitDwarfOutput, Diags, IsBinary);
 
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.
@@ -527,8 +527,8 @@
   if (Failed) {
     if (Opts.OutputPath != "-")
       sys::fs::remove(Opts.OutputPath);
-    if (!Opts.SplitDwarfFile.empty() && Opts.SplitDwarfFile != "-")
-      sys::fs::remove(Opts.SplitDwarfFile);
+    if (!Opts.SplitDwarfOutput.empty() && Opts.SplitDwarfOutput != "-")
+      sys::fs::remove(Opts.SplitDwarfOutput);
   }
 
   return Failed;