4 files changed, 27 insertions, 7 deletions
diff --git a/llvm/lib/Support/PrettyStackTrace.cpp b/llvm/lib/Support/PrettyStackTrace.cpp
index 82b0e6a..eff9947 100644
--- a/llvm/lib/Support/PrettyStackTrace.cpp
+++ b/llvm/lib/Support/PrettyStackTrace.cpp
@@ -141,7 +141,7 @@ extern "C" const char *__crashreporter_info__
 asm(".desc ___crashreporter_info__, 0x10");
 #endif
 
-static void setCrashLogMessage(const char *msg) LLVM_ATTRIBUTE_UNUSED;
+[[maybe_unused]] static void setCrashLogMessage(const char *msg);
 static void setCrashLogMessage(const char *msg) {
 #ifdef HAVE_CRASHREPORTERCLIENT_H
   (void)CRSetCrashLogMessage(msg);
diff --git a/llvm/lib/Support/SourceMgr.cpp b/llvm/lib/Support/SourceMgr.cpp
index a43cf37a..f2bbaab 100644
--- a/llvm/lib/Support/SourceMgr.cpp
+++ b/llvm/lib/Support/SourceMgr.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SMLoc.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
@@ -38,6 +39,22 @@ using namespace llvm;
 
 static const size_t TabStop = 8;
 
+// Out of line to avoid needing definition of vfs::FileSystem in header.
+SourceMgr::SourceMgr() = default;
+SourceMgr::SourceMgr(IntrusiveRefCntPtr<vfs::FileSystem> FS)
+    : FS(std::move(FS)) {}
+SourceMgr::SourceMgr(SourceMgr &&) = default;
+SourceMgr &SourceMgr::operator=(SourceMgr &&) = default;
+SourceMgr::~SourceMgr() = default;
+
+IntrusiveRefCntPtr<vfs::FileSystem> SourceMgr::getVirtualFileSystem() const {
+  return FS;
+}
+
+void SourceMgr::setVirtualFileSystem(IntrusiveRefCntPtr<vfs::FileSystem> FS) {
+  this->FS = std::move(FS);
+}
+
 unsigned SourceMgr::AddIncludeFile(const std::string &Filename,
                                    SMLoc IncludeLoc,
                                    std::string &IncludedFile) {
@@ -52,8 +69,11 @@ unsigned SourceMgr::AddIncludeFile(const std::string &Filename,
 ErrorOr<std::unique_ptr<MemoryBuffer>>
 SourceMgr::OpenIncludeFile(const std::string &Filename,
                            std::string &IncludedFile) {
+  if (!FS)
+    reportFatalInternalError("Opening include file from SourceMgr without VFS");
+
   ErrorOr<std::unique_ptr<MemoryBuffer>> NewBufOrErr =
-      MemoryBuffer::getFile(Filename);
+      FS->getBufferForFile(Filename);
 
   SmallString<64> Buffer(Filename);
   // If the file didn't exist directly, see if it's in an include path.
@@ -61,7 +81,7 @@ SourceMgr::OpenIncludeFile(const std::string &Filename,
        ++i) {
     Buffer = IncludeDirectories[i];
     sys::path::append(Buffer, Filename);
-    NewBufOrErr = MemoryBuffer::getFile(Buffer);
+    NewBufOrErr = FS->getBufferForFile(Buffer);
   }
 
   if (NewBufOrErr)
diff --git a/llvm/lib/Support/TextEncoding.cpp b/llvm/lib/Support/TextEncoding.cpp
index 804ff07..41f5187 100644
--- a/llvm/lib/Support/TextEncoding.cpp
+++ b/llvm/lib/Support/TextEncoding.cpp
@@ -54,9 +54,9 @@ static std::optional<TextEncoding> getKnownEncoding(StringRef Name) {
   return std::nullopt;
 }
 
-LLVM_ATTRIBUTE_UNUSED static void
-HandleOverflow(size_t &Capacity, char *&Output, size_t &OutputLength,
-               SmallVectorImpl<char> &Result) {
+[[maybe_unused]] static void HandleOverflow(size_t &Capacity, char *&Output,
+                                            size_t &OutputLength,
+                                            SmallVectorImpl<char> &Result) {
   // No space left in output buffer. Double the size of the underlying
   // memory in the SmallVectorImpl, adjust pointer and length and continue
   // the conversion.
diff --git a/llvm/lib/Support/UnicodeNameToCodepoint.cpp b/llvm/lib/Support/UnicodeNameToCodepoint.cpp
index 8d66348..6f8e091 100644
--- a/llvm/lib/Support/UnicodeNameToCodepoint.cpp
+++ b/llvm/lib/Support/UnicodeNameToCodepoint.cpp
@@ -476,7 +476,7 @@ nearestMatchesForCodepointName(StringRef Pattern, std::size_t MaxMatchesCount) {
       std::min(NormalizedName.size(), UnicodeNameToCodepointLargestNameSize) +
       1;
 
-  LLVM_ATTRIBUTE_UNUSED static std::size_t Rows =
+  [[maybe_unused]] static std::size_t Rows =
       UnicodeNameToCodepointLargestNameSize + 1;
 
   std::vector<char> Distances(