Revert r70075 and r70078, which reorganized the PCH on-disk hash table

for identifiers to separate "interesting" from "uninteresting"
identifiers. However, to cope with compiler invocations where the
predefines buffers mismatch, we need to be able to search the complete
identifier table. Cocoa.h.pch is now about 500k larger that it used to
be :(

llvm-svn: 70320

clang/lib/Frontend/PCHReader.cpp

@@ -1943,47 +1943,14 @@ IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
     uint32_t Offset = IdentifierOffsets[ID - 1];
     const char *Str = IdentifierTableData + Offset;
 
-    // If there is an identifier lookup table, but the offset of this
-    // string is after the identifier table itself, then we know that
-    // this string is not in the on-disk hash table. Therefore,
-    // disable lookup into the hash table when looking for this
-    // identifier.
-    PCHIdentifierLookupTable *IdTable 
-      = (PCHIdentifierLookupTable *)IdentifierLookupTable;
-    if (!IdTable ||
-        Offset >= uint32_t(IdTable->getBuckets() - IdTable->getBase())) {
-      // Turn off lookup into the on-disk hash table. We know that
-      // this identifier is not there.
-      if (IdTable)
-        PP.getIdentifierTable().setExternalIdentifierLookup(0);
-
-      // All of the strings in the PCH file are preceded by a 16-bit
-      // length. Extract that 16-bit length to avoid having to execute
-      // strlen().
-      const char *StrLenPtr = Str - 2;
-      unsigned StrLen = (((unsigned) StrLenPtr[0])
-                         | (((unsigned) StrLenPtr[1]) << 8)) - 1;
-      IdentifiersLoaded[ID - 1]=&PP.getIdentifierTable().get(Str, Str + StrLen);
-
-      // Turn on lookup into the on-disk hash table, if we have an
-      // on-disk hash table.
-      if (IdTable)
-        PP.getIdentifierTable().setExternalIdentifierLookup(this);
-    } else {
-      // The identifier is a key in our on-disk hash table. Since we
-      // know where the hash table entry starts, just read in this
-      // (key, value) pair.
-      PCHIdentifierLookupTrait Trait(const_cast<PCHReader &>(*this));
-      const unsigned char *Pos = (const unsigned char *)Str - 4;
-      std::pair<unsigned, unsigned> KeyDataLengths
-        = Trait.ReadKeyDataLength(Pos);
-
-      PCHIdentifierLookupTrait::internal_key_type InternalKey
-        = Trait.ReadKey(Pos, KeyDataLengths.first);
-      Pos = (const unsigned char *)Str + KeyDataLengths.first;
-      IdentifiersLoaded[ID - 1] = Trait.ReadData(InternalKey, Pos,
-                                                 KeyDataLengths.second);
-    }
+    // All of the strings in the PCH file are preceded by a 16-bit
+    // length. Extract that 16-bit length to avoid having to execute
+    // strlen().
+    const char *StrLenPtr = Str - 2;
+    unsigned StrLen = (((unsigned) StrLenPtr[0])
+                       | (((unsigned) StrLenPtr[1]) << 8)) - 1;
+    IdentifiersLoaded[ID - 1] 
+      = &PP.getIdentifierTable().get(Str, Str + StrLen);
   }
   
   return IdentifiersLoaded[ID - 1];