Index: tools/llvm-lto/llvm-lto.cpp
===================================================================
--- tools/llvm-lto/llvm-lto.cpp
+++ tools/llvm-lto/llvm-lto.cpp
@@ -484,6 +484,7 @@
     ThinGenerator.setCacheMaxSizeFiles(ThinLTOCacheMaxSizeFiles);
     ThinGenerator.setCacheMaxSizeBytes(ThinLTOCacheMaxSizeBytes);
     ThinGenerator.setFreestanding(EnableFreestanding);
+    ThinGenerator.setOptLevel(OptLevel - '0');
 
     // Add all the exported symbols to the table of symbols to preserve.
     for (unsigned i = 0; i < ExportedSymbols.size(); ++i)