================ Comment at: lib/CodeGen/BackendUtil.cpp:190 @@ +189,3 @@ + // MemorySanitizer. + if (Builder.OptLevel > 0) { + PM.add(createEarlyCSEPass()); ---------------- I think that some comment mentioning the "difference" made by each optimization would be nice. http://llvm-reviews.chandlerc.com/D189