Cleanups in IdentifierInfo following the removal of PTH

[riccibruno]

Summary

Conditional on D54547: PTH-- Remove feature entirely-

The Entry pointer in IdentifierInfo was only null for IdentifierInfos
created from a PTH. Now that PTH support has been removed we can remove
some PTH specific code in IdentifierInfo::getLength and IdentifierInfo::getNameStart.

Also make the constructor of IdentifierInfo private to make sure that they
are only created by IdentifierTable, and move it to the header so that it
can be inlined in IdentifierTable::get and IdentifierTable::getOwn.

[erichkeane]

This looks right to me. Note the PTH removal is still waiting approval.

include/clang/Basic/IdentifierTable.h

119

Instead of putting these in an initializer, can you default-init each of them inline, then make this =default?

[riccibruno]

include/clang/Basic/IdentifierTable.h

119

Nope, you cannot default-init bit-fields (at least not until c++20)

[erichkeane]

include/clang/Basic/IdentifierTable.h

119

Ugg, you're right. I hate bitfields.

[riccibruno]

include/clang/Basic/IdentifierTable.h

119

Happy monday morning :)

[riccibruno]

Can this go in now that D54547 has been committed ?

include/clang/Basic/IdentifierTable.h

class alignas(IdentifierInfoAlignment) IdentifierInfo {
 
   // 29 bits left in a 64-bit word.
 
   // Managed by the language front-end.
   void *FETokenInfo = nullptr;
 
   llvm::StringMapEntry<IdentifierInfo *> *Entry = nullptr;
 
+  IdentifierInfo()
+      : TokenID(tok::identifier), ObjCOrBuiltinID(0), HasMacro(false),
+        HadMacro(false), IsExtension(false), IsFutureCompatKeyword(false),
+        IsPoisoned(false), IsCPPOperatorKeyword(false),
+        NeedsHandleIdentifier(false), IsFromAST(false), ChangedAfterLoad(false),
+        FEChangedAfterLoad(false), RevertedTokenID(false), OutOfDate(false),
+        IsModulesImport(false) {}
+
 public:
-  IdentifierInfo();
   IdentifierInfo(const IdentifierInfo &) = delete;
   IdentifierInfo &operator=(const IdentifierInfo &) = delete;
+  IdentifierInfo(IdentifierInfo &&) = delete;
+  IdentifierInfo &operator=(IdentifierInfo &&) = delete;
 
   /// Return true if this is the identifier for the specified string.
   ///
   /// This is intended to be used for string literals only: II->isStr("foo").
   template <std::size_t StrLen>
   bool isStr(const char (&Str)[StrLen]) const {
     return getLength() == StrLen-1 &&
            memcmp(getNameStart(), Str, StrLen-1) == 0;
   }
 
   /// Return true if this is the identifier for the specified StringRef.
   bool isStr(llvm::StringRef Str) const {
     llvm::StringRef ThisStr(getNameStart(), getLength());
     return ThisStr == Str;
   }
 
   /// Return the beginning of the actual null-terminated string for this
   /// identifier.
-  const char *getNameStart() const {
-    if (Entry) return Entry->getKeyData();
-    // FIXME: This is gross. It would be best not to embed specific details
-    // of the PTH file format here.
-    // The 'this' pointer really points to a
-    // std::pair<IdentifierInfo, const char*>, where internal pointer
-    // points to the external string data.
-    using actualtype = std::pair<IdentifierInfo, const char *>;
-
-    return ((const actualtype*) this)->second;
-  }
+  const char *getNameStart() const { return Entry->getKeyData(); }
 
   /// Efficiently return the length of this identifier info.
-  unsigned getLength() const {
-    if (Entry) return Entry->getKeyLength();
-    // FIXME: This is gross. It would be best not to embed specific details
-    // of the PTH file format here.
-    // The 'this' pointer really points to a
-    // std::pair<IdentifierInfo, const char*>, where internal pointer
-    // points to the external string data.
-    using actualtype = std::pair<IdentifierInfo, const char *>;
-
-    const char* p = ((const actualtype*) this)->second - 2;
-    return (((unsigned) p[0]) | (((unsigned) p[1]) << 8)) - 1;
-  }
+  unsigned getLength() const { return Entry->getKeyLength(); }
 
   /// Return the actual identifier string.
   StringRef getName() const {
     return StringRef(getNameStart(), getLength());
   }
 
   /// Return true if this identifier is \#defined to some other value.
   /// \note The current definition may be in a module and not currently visible.

lib/Basic/IdentifierTable.cpp

 #include <cassert>
 #include <cstdio>
 #include <cstring>
 #include <string>
 
 using namespace clang;
 
 //===----------------------------------------------------------------------===//
-// IdentifierInfo Implementation
-//===----------------------------------------------------------------------===//
-
-IdentifierInfo::IdentifierInfo() {
-  TokenID = tok::identifier;
-  ObjCOrBuiltinID = 0;
-  HasMacro = false;
-  HadMacro = false;
-  IsExtension = false;
-  IsFutureCompatKeyword = false;
-  IsPoisoned = false;
-  IsCPPOperatorKeyword = false;
-  NeedsHandleIdentifier = false;
-  IsFromAST = false;
-  ChangedAfterLoad = false;
-  FEChangedAfterLoad = false;
-  RevertedTokenID = false;
-  OutOfDate = false;
-  IsModulesImport = false;
-}
-
-//===----------------------------------------------------------------------===//
 // IdentifierTable Implementation
 //===----------------------------------------------------------------------===//
 
 IdentifierIterator::~IdentifierIterator() = default;
 
 IdentifierInfoLookup::~IdentifierInfoLookup() = default;
 
 namespace {