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/clang/test/CodeGen/use-target-path-separator.c b/clang/test/CodeGen/use-target-path-separator.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/use-target-path-separator.c
@@ -0,0 +1,11 @@
+// RUN: rm -rf %t-dir
+// RUN: mkdir -p %t-dir/subdir
+// RUN: cd %t-dir
+// RUN: %clang_cl --target=x86_64-windows-msvc -ffile-reproducible /c /Z7 -fdebug-compilation-dir=. /Fosubdir/win.obj -- %s
+// RUN: llvm-readobj --codeview subdir/win.obj | FileCheck --check-prefix=WIN %s
+
+int main (void) {
+  return 0;
+}
+
+// WIN: ObjectName: subdir\win.obj
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;
   }