Index: cfe/trunk/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/Clang.cpp
+++ cfe/trunk/lib/Driver/ToolChains/Clang.cpp
@@ -3949,7 +3949,7 @@
   const char *SplitDWARFOut;
   if (SplitDWARF) {
     CmdArgs.push_back("-split-dwarf-file");
-    SplitDWARFOut = SplitDebugName(Args, Input, Output);
+    SplitDWARFOut = SplitDebugName(Args, Output);
     CmdArgs.push_back(SplitDWARFOut);
   }
 
@@ -5916,7 +5916,7 @@
   if ((getDebugFissionKind(D, Args, A) == DwarfFissionKind::Split) &&
       (T.isOSLinux() || T.isOSFuchsia())) {
     CmdArgs.push_back("-split-dwarf-file");
-    CmdArgs.push_back(SplitDebugName(Args, Input, Output));
+    CmdArgs.push_back(SplitDebugName(Args, Output));
   }
 
   assert(Input.isFilename() && "Invalid input.");
Index: cfe/trunk/lib/Driver/ToolChains/CommonArgs.h
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/CommonArgs.h
+++ cfe/trunk/lib/Driver/ToolChains/CommonArgs.h
@@ -63,7 +63,7 @@
                         const Tool &T);
 
 const char *SplitDebugName(const llvm::opt::ArgList &Args,
-                           const InputInfo &Input, const InputInfo &Output);
+                           const InputInfo &Output);
 
 void SplitDebugInfo(const ToolChain &TC, Compilation &C, const Tool &T,
                     const JobAction &JA, const llvm::opt::ArgList &Args,
Index: cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp
+++ cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp
@@ -808,26 +808,18 @@
   return false;
 }
 
-const char *tools::SplitDebugName(const ArgList &Args, const InputInfo &Input,
+const char *tools::SplitDebugName(const ArgList &Args,
                                   const InputInfo &Output) {
+  SmallString<128> F(Output.isFilename()
+                         ? Output.getFilename()
+                         : llvm::sys::path::stem(Output.getBaseInput()));
+
   if (Arg *A = Args.getLastArg(options::OPT_gsplit_dwarf_EQ))
     if (StringRef(A->getValue()) == "single")
-      return Args.MakeArgString(Output.getFilename());
+      return Args.MakeArgString(F);
 
-  Arg *FinalOutput = Args.getLastArg(options::OPT_o);
-  if (FinalOutput && Args.hasArg(options::OPT_c)) {
-    SmallString<128> T(FinalOutput->getValue());
-    llvm::sys::path::replace_extension(T, "dwo");
-    return Args.MakeArgString(T);
-  } else {
-    // Use the compilation dir.
-    SmallString<128> T(
-        Args.getLastArgValue(options::OPT_fdebug_compilation_dir));
-    SmallString<128> F(llvm::sys::path::stem(Input.getBaseInput()));
-    llvm::sys::path::replace_extension(F, "dwo");
-    T += F;
-    return Args.MakeArgString(F);
-  }
+  llvm::sys::path::replace_extension(F, "dwo");
+  return Args.MakeArgString(F);
 }
 
 void tools::SplitDebugInfo(const ToolChain &TC, Compilation &C, const Tool &T,
Index: cfe/trunk/lib/Driver/ToolChains/Gnu.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/Gnu.cpp
+++ cfe/trunk/lib/Driver/ToolChains/Gnu.cpp
@@ -817,7 +817,7 @@
   if (Args.hasArg(options::OPT_gsplit_dwarf) &&
       getToolChain().getTriple().isOSLinux())
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
-                   SplitDebugName(Args, Inputs[0], Output));
+                   SplitDebugName(Args, Output));
 }
 
 namespace {
Index: cfe/trunk/lib/Driver/ToolChains/MinGW.cpp
===================================================================
--- cfe/trunk/lib/Driver/ToolChains/MinGW.cpp
+++ cfe/trunk/lib/Driver/ToolChains/MinGW.cpp
@@ -54,7 +54,7 @@
 
   if (Args.hasArg(options::OPT_gsplit_dwarf))
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
-                   SplitDebugName(Args, Inputs[0], Output));
+                   SplitDebugName(Args, Output));
 }
 
 void tools::MinGW::Linker::AddLibGCC(const ArgList &Args,
Index: cfe/trunk/test/Tooling/clang-check-extra-arg.cpp
===================================================================
--- cfe/trunk/test/Tooling/clang-check-extra-arg.cpp
+++ cfe/trunk/test/Tooling/clang-check-extra-arg.cpp
@@ -2,4 +2,8 @@
 
 // CHECK: unknown warning option '-Wunimplemented-warning-before'
 // CHECK: unknown warning option '-Wunimplemented-warning'
+
+// Check we do not crash with -extra-arg=-gsplit-dwarf (we did, under linux).
+// RUN: clang-check "%s" -extra-arg=-gsplit-dwarf -- -c
+
 void a(){}