Index: lib/Support/Compression.cpp
===================================================================
--- lib/Support/Compression.cpp
+++ lib/Support/Compression.cpp
@@ -61,7 +61,7 @@
                      SmallVectorImpl<char> &CompressedBuffer,
                      CompressionLevel Level) {
   unsigned long CompressedSize = ::compressBound(InputBuffer.size());
-  CompressedBuffer.resize(CompressedSize);
+  CompressedBuffer.reserve(CompressedSize);
   int CLevel = encodeZlibCompressionLevel(Level);
   int Res = ::compress2((Bytef *)CompressedBuffer.data(), &CompressedSize,
                         (const Bytef *)InputBuffer.data(), InputBuffer.size(),
@@ -69,7 +69,7 @@
   // 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.resize(CompressedSize);
+  CompressedBuffer.set_size(CompressedSize);
   return Res ? createError(convertZlibCodeToString(Res)) : Error::success();
 }