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
@@ -443,6 +443,9 @@
       Dir = DirBuf;
       File = FileBuf;
     }
+  } else if (llvm::sys::path::is_absolute(FileName)) {
+    Dir = llvm::sys::path::parent_path(RemappedFile);
+    File = llvm::sys::path::filename(RemappedFile);
   } else {
     Dir = CurDir;
     File = RemappedFile;
diff --git a/clang/test/CodeGen/relative-debug-prefix-map.c b/clang/test/CodeGen/relative-debug-prefix-map.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/relative-debug-prefix-map.c
@@ -0,0 +1,17 @@
+// RUN: mkdir -p %t.nested/dir && cd %t.nested/dir
+// RUN: cp %s %t.nested/dir/main.c
+// RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%t.nested=. %t.nested/dir/main.c -emit-llvm -o - | FileCheck %s
+//
+// RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-prefix-map=%p=. %s -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-DIRECT
+//
+// RUN: cd %p
+// RUN: %clang_cc1 -debug-info-kind=standalone -fdebug-compilation-dir=. relative-debug-prefix-map.c -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-DIRECT
+
+// CHECK: !DIFile(filename: "main.c", directory: "./dir")
+// CHECK-DIRECT: !DIFile(filename: "relative-debug-prefix-map.c", directory: ".")
+
+int main(int argc, char **argv) {
+  (void)argc;
+  (void)argv;
+  return 0;
+}
diff --git a/clang/test/Modules/module-debuginfo-prefix.m b/clang/test/Modules/module-debuginfo-prefix.m
--- a/clang/test/Modules/module-debuginfo-prefix.m
+++ b/clang/test/Modules/module-debuginfo-prefix.m
@@ -4,23 +4,21 @@
 // Modules:
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -x objective-c -fmodules -fmodule-format=obj \
-// RUN:   -fdebug-prefix-map=%S/Inputs=/OVERRIDE \
+// RUN:   -fdebug-prefix-map=%S%{fssep}Inputs=%{fssrcroot}OVERRIDE \
 // RUN:   -fimplicit-module-maps -DMODULES -fmodules-cache-path=%t %s \
 // RUN:   -I %S/Inputs -I %t -emit-llvm -o %t.ll \
 // RUN:   -mllvm -debug-only=pchcontainer &>%t-mod.ll
-// RUN: cat %t-mod.ll | FileCheck %s
+// RUN: cat %t-mod.ll | FileCheck %s -DROOT=%{fssrcroot} -DSEP=%{fssep}
 
 // PCH:
 // RUN: %clang_cc1 -x objective-c -emit-pch -fmodule-format=obj -I %S/Inputs \
-// RUN:   -fdebug-prefix-map=%S/Inputs=/OVERRIDE \
+// RUN:   -fdebug-prefix-map=%S%{fssep}Inputs=%{fssrcroot}OVERRIDE \
 // RUN:   -o %t.pch %S/Inputs/DebugObjC.h \
 // RUN:   -mllvm -debug-only=pchcontainer &>%t-pch.ll
-// RUN: cat %t-pch.ll | FileCheck %s
+// RUN: cat %t-pch.ll | FileCheck %s -DROOT=%{fssrcroot} -DSEP=%{fssep}
 
 #ifdef MODULES
 @import DebugObjC;
 #endif
 
-// Dir should always be empty, but on Windows we can't recognize /var
-// as being an absolute path.
-// CHECK: !DIFile(filename: "/OVERRIDE/DebugObjC.h", directory: "{{()|(.*:.*)}}")
+// CHECK: !DIFile(filename: "[[ROOT]]OVERRIDE[[SEP]]DebugObjC.h", directory: "")