diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -479,9 +479,9 @@
   /// The seed used by the randomize structure layout feature.
   std::string RandstructSeed;
 
-  /// Indicates whether the __FILE__ macro should use the target's
-  /// platform-specific file separator or whether it should use the build
-  /// environment's platform-specific file separator.
+  /// Indicates whether to use target's platform-specific file separator when
+  /// __FILE__ macro is used and when concatenating filename with directory or
+  /// to use build environment environment's platform-specific file separator.
   ///
   /// The plaform-specific path separator is the backslash(\) for Windows and
   /// forward slash (/) elsewhere.
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
@@ -433,6 +433,7 @@
   Options.XRayOmitFunctionIndex = CodeGenOpts.XRayOmitFunctionIndex;
   Options.LoopAlignment = CodeGenOpts.LoopAlignment;
   Options.DebugStrictDwarf = CodeGenOpts.DebugStrictDwarf;
+  Options.UseTargetPathSeparator = LangOpts.UseTargetPathSeparator;
   Options.ObjectFilenameForDebug = CodeGenOpts.ObjectFilenameForDebug;
   Options.Hotpatch = CodeGenOpts.HotPatch;
   Options.JMCInstrument = CodeGenOpts.JMCInstrument;
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -528,6 +528,7 @@
   // Get absolute path name.
   SourceManager &SM = CGM.getContext().getSourceManager();
   auto &CGO = CGM.getCodeGenOpts();
+  const LangOptions &LO = CGM.getLangOpts();
   std::string MainFileName = CGO.MainFileName;
   if (MainFileName.empty())
     MainFileName = "<stdin>";
@@ -542,9 +543,15 @@
     MainFileDir = std::string(MainFile->getDir().getName());
     if (!llvm::sys::path::is_absolute(MainFileName)) {
       llvm::SmallString<1024> MainFileDirSS(MainFileDir);
-      llvm::sys::path::append(MainFileDirSS, MainFileName);
-      MainFileName =
-          std::string(llvm::sys::path::remove_leading_dotslash(MainFileDirSS));
+      llvm::sys::path::Style Style =
+          LO.UseTargetPathSeparator
+              ? (CGM.getTarget().getTriple().isOSWindows()
+                     ? llvm::sys::path::Style::windows_backslash
+                     : llvm::sys::path::Style::posix)
+              : llvm::sys::path::Style::native;
+      llvm::sys::path::append(MainFileDirSS, Style, MainFileName);
+      MainFileName = std::string(
+          llvm::sys::path::remove_leading_dotslash(MainFileDirSS, Style));
     }
     // If the main file name provided is identical to the input file name, and
     // if the input file is a preprocessed source, use the module name for
@@ -560,7 +567,6 @@
   }
 
   llvm::dwarf::SourceLanguage LangTag;
-  const LangOptions &LO = CGM.getLangOpts();
   if (LO.CPlusPlus) {
     if (LO.ObjC)
       LangTag = llvm::dwarf::DW_LANG_ObjC_plus_plus;
diff --git a/clang/test/CodeGen/debug-info-slash.c b/clang/test/CodeGen/debug-info-slash.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/debug-info-slash.c
@@ -0,0 +1,6 @@
+// RUN: %clang -target x86_64-pc-win32  -ffile-reproducible -emit-llvm -S -g %s -o - | FileCheck --check-prefix=WIN %s
+// RUN: %clang -target x86_64-linux-gnu  -ffile-reproducible -emit-llvm -S -g %s -o - | FileCheck --check-prefix=LINUX %s
+int main() { return 0; }
+
+// WIN:   !DIFile(filename: "{{.*}}\\debug-info-slash.c"
+// LINUX: !DIFile(filename: "{{.*}}/debug-info-slash.c"
diff --git a/llvm/include/llvm/CodeGen/CommandFlags.h b/llvm/include/llvm/CodeGen/CommandFlags.h
--- a/llvm/include/llvm/CodeGen/CommandFlags.h
+++ b/llvm/include/llvm/CodeGen/CommandFlags.h
@@ -145,6 +145,8 @@
 
 bool getXCOFFReadOnlyPointers();
 
+bool getUseTargetPathSeparator();
+
 /// Create this object with static storage to register codegen-related command
 /// line options.
 struct RegisterCodeGenFlags {
diff --git a/llvm/include/llvm/Target/TargetOptions.h b/llvm/include/llvm/Target/TargetOptions.h
--- a/llvm/include/llvm/Target/TargetOptions.h
+++ b/llvm/include/llvm/Target/TargetOptions.h
@@ -127,7 +127,8 @@
         : UnsafeFPMath(false), NoInfsFPMath(false), NoNaNsFPMath(false),
           NoTrappingFPMath(true), NoSignedZerosFPMath(false),
           ApproxFuncFPMath(false), EnableAIXExtendedAltivecABI(false),
-          HonorSignDependentRoundingFPMathOption(false), NoZerosInBSS(false),
+          HonorSignDependentRoundingFPMathOption(false),
+          UseTargetPathSeparator(false), NoZerosInBSS(false),
           GuaranteedTailCallOpt(false), StackSymbolOrdering(true),
           EnableFastISel(false), EnableGlobalISel(false), UseInitArray(false),
           DisableIntegratedAS(false), RelaxELFRelocations(true),
@@ -206,6 +207,11 @@
     unsigned HonorSignDependentRoundingFPMathOption : 1;
     bool HonorSignDependentRoundingFPMath() const;
 
+    /// UseTargetPathSeparator - This Indicates whether to use target's
+    /// platform-specific file separator when concatenating filename with
+    /// directory.
+    unsigned UseTargetPathSeparator : 1;
+
     /// NoZerosInBSS - By default some codegens place zero-initialized data to
     /// .bss section. This flag disables such behaviour (necessary, e.g. for
     /// crt*.o compiling).
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -791,7 +791,15 @@
     // Don't emit the filename if we're writing to stdout or to /dev/null.
     PathRef = {};
   } else {
-    llvm::sys::path::remove_dots(PathStore, /*remove_dot_dot=*/true);
+    llvm::sys::path::Style Style =
+        (!llvm::sys::path::is_absolute(PathRef,
+                                       llvm::sys::path::Style::posix) &&
+         Asm->TM.Options.UseTargetPathSeparator)
+            ? (Asm->TM.getTargetTriple().isOSWindows()
+                   ? llvm::sys::path::Style::windows_backslash
+                   : llvm::sys::path::Style::posix)
+            : llvm::sys::path::Style::native;
+    llvm::sys::path::remove_dots(PathStore, /*remove_dot_dot=*/true, Style);
     PathRef = PathStore;
   }
 
diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -104,6 +104,7 @@
 CGOPT(unsigned, AlignLoops)
 CGOPT(bool, JMCInstrument)
 CGOPT(bool, XCOFFReadOnlyPointers)
+CGOPT(bool, UseTargetPathSeparator)
 
 codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
 #define CGBINDOPT(NAME)                                                        \
@@ -486,6 +487,14 @@
       cl::init(false));
   CGBINDOPT(XCOFFReadOnlyPointers);
 
+  static cl::opt<bool> UseTargetPathSeparator(
+      "use-target-path-separator",
+      cl::desc(
+          "Use target's platform-specific file separator when concatenating "
+          "filename with directory."),
+      cl::init(false));
+  CGBINDOPT(UseTargetPathSeparator);
+
 #undef CGBINDOPT
 
   mc::RegisterMCTargetOptionsFlags();
@@ -563,6 +572,7 @@
   Options.LoopAlignment = getAlignLoops();
   Options.JMCInstrument = getJMCInstrument();
   Options.XCOFFReadOnlyPointers = getXCOFFReadOnlyPointers();
+  Options.UseTargetPathSeparator = getUseTargetPathSeparator();
 
   Options.MCOptions = mc::InitMCTargetOptionsFromFlags();
 
diff --git a/llvm/test/DebugInfo/COFF/use-target-path-separator.ll b/llvm/test/DebugInfo/COFF/use-target-path-separator.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/DebugInfo/COFF/use-target-path-separator.ll
@@ -0,0 +1,35 @@
+; RUN: rm -rf %t-dir
+; RUN: mkdir -p %t-dir/subdir
+; RUN: cd %t-dir
+; RUN: llc -filetype=obj -mtriple i686-pc-windows-msvc -use-target-path-separator %s -o subdir/win.obj
+; RUN: llvm-readobj --codeview subdir/win.obj | FileCheck --check-prefix=WIN %s
+
+; WIN: ObjectName: subdir\win.obj
+
+; ModuleID = 'D:\src\scopes\foo.cpp'
+source_filename = "D:\5Csrc\5Cscopes\5Cfoo.cpp"
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc19.0.23918"
+
+define i32 @"?foo@@YAHXZ"() !dbg !10 {
+entry:
+  ret i32 42, !dbg !14
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 4.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+; One .debug$S section should contain an S_COMPILE3 record that identifies the
+; source language and the version of the compiler based on the DICompileUnit.
+!1 = !DIFile(filename: "D:\5Csrc\5Cscopes\5Cfoo.cpp", directory: "D:\5Csrc\5Cscopes\5Cclang")
+!2 = !{}
+!7 = !{i32 2, !"CodeView", i32 1}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 4.0.0 "}
+!10 = distinct !DISubprogram(name: "foo", linkageName: "\01?foo@@YAHXZ", scope: !1, file: !1, line: 1, type: !11, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!11 = !DISubroutineType(types: !12)
+!12 = !{!13}
+!13 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!14 = !DILocation(line: 2, scope: !10)