Index: lld/COFF/PDB.cpp
===================================================================
--- lld/COFF/PDB.cpp
+++ lld/COFF/PDB.cpp
@@ -222,7 +222,7 @@
 // PDB to work without additional configuration:
 // https://docs.microsoft.com/en-us/visualstudio/debugger/debug-source-files-common-properties-solution-property-pages-dialog-box
 static void pdbMakeAbsolute(SmallVectorImpl<char> &FileName) {
-  if (sys::path::is_absolute(FileName, sys::path::Style::windows))
+  if (sys::path::is_absolute(FileName))
     return;
   if (Config->PDBSourcePath.empty()) {
     // Debuggers generally want that PDB files contain absolute, Windows-style
@@ -238,10 +238,9 @@
   // PDBSourcePath to the absolute POSIX path. Since absolute POSIX paths
   // don't make sense in PDB files anyways, this is gargabe-in-garbage-out.
   SmallString<128> AbsoluteFileName = Config->PDBSourcePath;
-  sys::path::append(AbsoluteFileName, sys::path::Style::windows, FileName);
-  sys::path::native(AbsoluteFileName, sys::path::Style::windows);
-  sys::path::remove_dots(AbsoluteFileName, /*remove_dot_dots=*/true,
-                         sys::path::Style::windows);
+  sys::path::append(AbsoluteFileName, FileName);
+  sys::path::native(AbsoluteFileName);
+  sys::path::remove_dots(AbsoluteFileName, /*remove_dot_dots=*/true);
   FileName = std::move(AbsoluteFileName);
 }
 
@@ -444,8 +443,7 @@
         StringRef LocalPath =
             !File->ParentName.empty() ? File->ParentName : File->getName();
         SmallString<128> Path = sys::path::parent_path(LocalPath);
-        sys::path::append(
-            Path, sys::path::filename(TSPath, sys::path::Style::windows));
+        sys::path::append(Path, sys::path::filename(TSPath));
         return tryToLoadPDB(TSId, Path);
       },
       [&](std::unique_ptr<ECError> EC) -> Error {
@@ -1027,7 +1025,7 @@
   bool InArchive = !File->ParentName.empty();
   SmallString<128> Path = InArchive ? File->ParentName : File->getName();
   pdbMakeAbsolute(Path);
-  sys::path::native(Path, sys::path::Style::windows);
+  sys::path::native(Path);
   StringRef Name = InArchive ? File->getName() : StringRef(Path);
 
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
@@ -1312,7 +1310,7 @@
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
   NativePath = Config->PDBPath;
   pdbMakeAbsolute(NativePath);
-  sys::path::native(NativePath, sys::path::Style::windows);
+  sys::path::native(NativePath);
   uint32_t PdbFilePathNI = DbiBuilder.addECName(NativePath);
   auto &LinkerModule = ExitOnErr(DbiBuilder.addModuleInfo("* Linker *"));
   LinkerModule.setPdbFilePathNI(PdbFilePathNI);
Index: lldb/lit/SymbolFile/NativePDB/source-list.cpp
===================================================================
--- lldb/lit/SymbolFile/NativePDB/source-list.cpp
+++ lldb/lit/SymbolFile/NativePDB/source-list.cpp
@@ -25,7 +25,7 @@
 // changing this file.
 
 // CHECK: (lldb) source list -n main
-// CHECK: File: D:\src\llvm-mono\lldb\lit\SymbolFile\NativePDB\source-list.cpp
+// CHECK: File: {{.*}}source-list.cpp
 // CHECK:    10
 // CHECK:    11    // Some context lines before
 // CHECK:    12   // the function.
Index: lldb/source/Plugins/SymbolFile/NativePDB/CompileUnitIndex.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/NativePDB/CompileUnitIndex.cpp
+++ lldb/source/Plugins/SymbolFile/NativePDB/CompileUnitIndex.cpp
@@ -42,11 +42,8 @@
   if (llvm::sys::fs::equivalent(main, other))
     return true;
 
-  // FIXME: If we ever want to support PDB debug info for non-Windows systems
-  // the following check will be wrong, but we need a way to store the host
-  // information in the PDB.
   llvm::SmallString<64> normalized(other);
-  llvm::sys::path::native(normalized, llvm::sys::path::Style::windows);
+  llvm::sys::path::native(normalized);
   return main.equals_lower(normalized);
 }
 
@@ -156,7 +153,8 @@
   // name until we find it, and we can cache that one since the memory is backed
   // by a contiguous chunk inside the mapped PDB.
   llvm::SmallString<64> main_file = GetMainSourceFile(*cci);
-  llvm::sys::path::native(main_file, llvm::sys::path::Style::windows);
+  std::string s = main_file.str();
+  llvm::sys::path::native(main_file);
 
   uint32_t file_count = modules.getSourceFileCount(modi);
   cci->m_file_list.reserve(file_count);
Index: lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
+++ lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp
@@ -530,7 +530,9 @@
   lldbassert(cci);
 
   for (llvm::StringRef f : cci->m_file_list) {
-    FileSpec spec(f, false, FileSpec::Style::windows);
+    FileSpec::Style style =
+        f.startswith("/") ? FileSpec::Style::posix : FileSpec::Style::windows;
+    FileSpec spec(f, false, style);
     support_files.Append(spec);
   }
 
Index: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -73,6 +73,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
@@ -134,7 +135,9 @@
 
   // If this is a Unix-style path, just use it as is. Don't try to canonicalize
   // it textually because one of the path components could be a symlink.
-  if (!Dir.empty() && Dir[0] == '/') {
+  if (Dir.startswith("/") || Filename.startswith("/")) {
+    if (llvm::sys::path::is_absolute(Filename, llvm::sys::path::Style::posix))
+      return Filename;
     Filepath = Dir;
     if (Dir.back() != '/')
       Filepath += '/';