Address comments.

Author: kazutakahirata

llvm/include/llvm/ProfileData/MemProfReader.h

@@ -214,10 +214,10 @@ class YAMLMemProfReader final : public MemProfReader {
 public:
   YAMLMemProfReader() = default;
 
-  // Return true if the \p DataBuffer starts "---" indicating it is a YAML file.
+  // Return true if the \p DataBuffer starts with "---" indicating it is a YAML
+  // file.
   static bool hasFormat(const MemoryBuffer &DataBuffer);
-  // Return true if the file at \p Path starts with magic bytes indicating it is
-  // a raw binary memprof profile.
+  // Wrapper around hasFormat above, reading the file instead of the memory buffer.
   static bool hasFormat(const StringRef Path);
 
   // Create a YAMLMemProfReader after sanity checking the contents of the file

llvm/lib/ProfileData/MemProfReader.cpp

@@ -767,7 +767,7 @@ YAMLMemProfReader::create(const Twine &Path) {
 
 Expected<std::unique_ptr<YAMLMemProfReader>>
 YAMLMemProfReader::create(std::unique_ptr<MemoryBuffer> Buffer) {
-  std::unique_ptr<YAMLMemProfReader> Reader(new YAMLMemProfReader());
+  auto Reader = std::make_unique<YAMLMemProfReader>();
   Reader->parse(Buffer->getBuffer());
   return std::move(Reader);
 }

llvm/tools/llvm-profdata/llvm-profdata.cpp

@@ -3271,22 +3271,16 @@ static int showMemProfProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
   if (SFormat == ShowFormat::Json)
     exitWithError("JSON output is not supported for MemProf");
 
-  // Load the file to check the magic bytes.
-  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> BufferOrError =
-      llvm::MemoryBuffer::getFile(Filename);
-  if (auto EC = BufferOrError.getError())
-    exitWithError("Error opening profile file '" + Filename + "'");
-  auto Buffer = std::move(BufferOrError.get());
-
   // Show the raw profile in YAML.
-  if (memprof::RawMemProfReader::hasFormat(*Buffer)) {
+  if (memprof::RawMemProfReader::hasFormat(Filename)) {
     auto ReaderOr = llvm::memprof::RawMemProfReader::create(
         Filename, ProfiledBinary, /*KeepNames=*/true);
-    if (Error E = ReaderOr.takeError())
+    if (Error E = ReaderOr.takeError()) {
       // Since the error can be related to the profile or the binary we do not
       // pass whence. Instead additional context is provided where necessary in
       // the error message.
       exitWithError(std::move(E), /*Whence*/ "");
+    }
 
     std::unique_ptr<llvm::memprof::RawMemProfReader> Reader(
         ReaderOr.get().release());