Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.

llvm-svn: 304638

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -2087,6 +2087,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     switch (I.getNumArgOperands()) {
     case 3:
       assert(isa<ConstantInt>(I.getArgOperand(2)) && "Invalid rounding mode");
+      LLVM_FALLTHROUGH;
     case 2:
       CopyOp = I.getArgOperand(0);
       ConvertOp = I.getArgOperand(1);