Replace "fallthrough" comments with LLVM_FALLTHROUGH

This is a mechanical change of comments in switches like fallthrough,
fall-through, or fall-thru to use the LLVM_FALLTHROUGH macro instead.

llvm-svn: 278902

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2271,7 +2271,7 @@ std::error_code BitcodeReader::parseMetadata(bool ModuleLevel) {
     }
     case bitc::METADATA_DISTINCT_NODE:
       IsDistinct = true;
-      // fallthrough...
+      LLVM_FALLTHROUGH;
     case bitc::METADATA_NODE: {
       SmallVector<Metadata *, 8> Elts;
       Elts.reserve(Record.size());
@@ -3355,7 +3355,7 @@ std::error_code BitcodeReader::parseUseLists() {
       break;
     case bitc::USELIST_CODE_BB:
       IsBB = true;
-      // fallthrough
+      LLVM_FALLTHROUGH;
     case bitc::USELIST_CODE_DEFAULT: {
       unsigned RecordLength = Record.size();
       if (RecordLength < 3)