Remove explicit seeds from string hashes that are compiler-dependent

The one for enum raw value checking isn't serialized anywhere, so we
can use normal in-process hashing. The ones in the Clang importer's
lookup tables are serialized, but the lookup table is already only
valid for a particular compiler build anyway (it goes into a Clang
PCM, which has the full compiler version in its cache key).

Author: jrose-apple

lib/ClangImporter/SwiftLookupTable.cpp

@@ -1090,8 +1090,7 @@ namespace {
     }
 
     hash_value_type ComputeHash(key_type_ref key) {
-      // FIXME: DJB seed=0, audit whether the default seed could be used.
-      return static_cast<unsigned>(key.first) + llvm::djbHash(key.second, 0);
+      return static_cast<unsigned>(key.first) + llvm::djbHash(key.second);
     }
 
     std::pair<unsigned, unsigned> EmitKeyDataLength(raw_ostream &out,
@@ -1340,8 +1339,7 @@ namespace {
     }
 
     hash_value_type ComputeHash(internal_key_type key) {
-      // FIXME: DJB seed=0, audit whether the default seed could be used.
-      return static_cast<unsigned>(key.first) + llvm::djbHash(key.second, 0);
+      return static_cast<unsigned>(key.first) + llvm::djbHash(key.second);
     }
 
     static bool EqualKey(internal_key_type lhs, internal_key_type rhs) {

lib/Sema/TypeCheckDecl.cpp

@@ -97,7 +97,6 @@ struct RawValueKey {
   // FIXME: doesn't accommodate >64-bit or signed raw integer or float values.
   union {
     StringRef stringValue;
-    uint32_t charValue;
     IntValueTy intValue;
     FloatValueTy floatValue;
   };
@@ -181,8 +180,7 @@ class DenseMapInfo<RawValueKey> {
       return DenseMapInfo<uint64_t>::getHashValue(k.intValue.v0) &
              DenseMapInfo<uint64_t>::getHashValue(k.intValue.v1);
     case RawValueKey::Kind::String:
-      // FIXME: DJB seed=0, audit whether the default seed could be used.
-      return llvm::djbHash(k.stringValue, 0);
+      return DenseMapInfo<StringRef>::getHashValue(k.stringValue);
     case RawValueKey::Kind::Empty:
     case RawValueKey::Kind::Tombstone:
       return 0;