Index: llvm/lib/Support/Compression.cpp
===================================================================
--- llvm/lib/Support/Compression.cpp
+++ llvm/lib/Support/Compression.cpp
@@ -49,14 +49,14 @@
 Error zlib::compress(StringRef InputBuffer,
                      SmallVectorImpl<char> &CompressedBuffer, int Level) {
   unsigned long CompressedSize = ::compressBound(InputBuffer.size());
-  CompressedBuffer.reserve(CompressedSize);
+  CompressedBuffer.resize_for_overwrite(CompressedSize);
   int Res =
       ::compress2((Bytef *)CompressedBuffer.data(), &CompressedSize,
                   (const Bytef *)InputBuffer.data(), InputBuffer.size(), Level);
   // Tell MemorySanitizer that zlib output buffer is fully initialized.
   // This avoids a false report when running LLVM with uninstrumented ZLib.
   __msan_unpoison(CompressedBuffer.data(), CompressedSize);
-  CompressedBuffer.set_size(CompressedSize);
+  CompressedBuffer.truncate(CompressedSize);
   return Res ? createError(convertZlibCodeToString(Res)) : Error::success();
 }
 
@@ -74,10 +74,10 @@
 Error zlib::uncompress(StringRef InputBuffer,
                        SmallVectorImpl<char> &UncompressedBuffer,
                        size_t UncompressedSize) {
-  UncompressedBuffer.reserve(UncompressedSize);
+  UncompressedBuffer.resize_for_overwrite(UncompressedSize);
   Error E =
       uncompress(InputBuffer, UncompressedBuffer.data(), UncompressedSize);
-  UncompressedBuffer.set_size(UncompressedSize);
+  UncompressedBuffer.truncate(UncompressedSize);
   return E;
 }
 
Index: llvm/lib/Support/Path.cpp
===================================================================
--- llvm/lib/Support/Path.cpp
+++ llvm/lib/Support/Path.cpp
@@ -474,7 +474,7 @@
 void remove_filename(SmallVectorImpl<char> &path, Style style) {
   size_t end_pos = parent_path_end(StringRef(path.begin(), path.size()), style);
   if (end_pos != StringRef::npos)
-    path.set_size(end_pos);
+    path.truncate(end_pos);
 }
 
 void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
@@ -486,7 +486,7 @@
   // Erase existing extension.
   size_t pos = p.find_last_of('.');
   if (pos != StringRef::npos && pos >= filename_pos(p, style))
-    path.set_size(pos);
+    path.truncate(pos);
 
   // Append '.' if needed.
   if (ext.size() > 0 && ext[0] != '.')