Re-land: "[Support] Replace HashString with djbHash."

This patch removes the HashString function from StringExtraces and
replaces its uses with calls to djbHash from DJB.h.

This change is *almost* NFC. While the algorithm is identical, the
djbHash implementation in StringExtras used 0 as its default seed while
the implementation in DJB uses 5381. The latter has been shown to result
in less collisions and improved avalanching and is used by the DWARF
accelerator tables.

Because some test were implicitly relying on the hash order, I've
reverted to using zero as a seed for the following two files:

  lld/include/lld/Core/SymbolTable.h
  llvm/lib/Support/StringMap.cpp

Differential revision: https://reviews.llvm.org/D43615

llvm-svn: 326091

clang/lib/Frontend/CacheTokens.cpp

@@ -21,8 +21,8 @@
 #include "clang/Lex/Lexer.h"
 #include "clang/Lex/PTHManager.h"
 #include "clang/Lex/Preprocessor.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
+#include "llvm/Support/DJB.h"
 #include "llvm/Support/EndianStream.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -128,7 +128,7 @@ class FileEntryPTHEntryInfo {
   typedef unsigned offset_type;
 
   static hash_value_type ComputeHash(PTHEntryKeyVariant V) {
-    return llvm::HashString(V.getString());
+    return llvm::djbHash(V.getString());
   }
 
   static std::pair<unsigned,unsigned>
@@ -625,7 +625,7 @@ class PTHIdentifierTableTrait {
   typedef unsigned offset_type;
 
   static hash_value_type ComputeHash(PTHIdKey* key) {
-    return llvm::HashString(key->II->getName());
+    return llvm::djbHash(key->II->getName());
   }
 
   static std::pair<unsigned,unsigned>

clang/lib/Lex/PTHLexer.cpp

@@ -23,8 +23,8 @@
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/Token.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/DJB.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/FileSystem.h"
@@ -145,7 +145,7 @@ bool PTHLexer::LexEndOfFile(Token &Result) {
     ParsingPreprocessorDirective = false; // Done parsing the "line".
     return true;  // Have a token.
   }
-  
+
   assert(!LexingRawMode);
 
   // If we are in a #if directive, emit an error.
@@ -336,7 +336,7 @@ class PTHFileLookupCommonTrait {
   using offset_type = unsigned;
 
   static hash_value_type ComputeHash(internal_key_type x) {
-    return llvm::HashString(x.second);
+    return llvm::djbHash(x.second);
   }
 
   static std::pair<unsigned, unsigned>
@@ -396,7 +396,7 @@ class PTHManager::PTHStringLookupTrait {
   }
 
   static hash_value_type ComputeHash(const internal_key_type& a) {
-    return llvm::HashString(StringRef(a.first, a.second));
+    return llvm::djbHash(StringRef(a.first, a.second));
   }
 
   // This hopefully will just get inlined and removed by the optimizer.

clang/lib/Serialization/ASTCommon.cpp

@@ -16,7 +16,7 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Serialization/ASTDeserializationListener.h"
-#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/DJB.h"
 
 using namespace clang;
 
@@ -171,7 +171,7 @@ unsigned serialization::ComputeHash(Selector Sel) {
   unsigned R = 5381;
   for (unsigned I = 0; I != N; ++I)
     if (IdentifierInfo *II = Sel.getIdentifierInfoForSlot(I))
-      R = llvm::HashString(II->getName(), R);
+      R = llvm::djbHash(II->getName(), R);
   return R;
 }
 
@@ -231,7 +231,7 @@ serialization::getDefinitiveDeclContext(const DeclContext *DC) {
   default:
     llvm_unreachable("Unhandled DeclContext in AST reader");
   }
-  
+
   llvm_unreachable("Unhandled decl kind");
 }
 

clang/lib/Serialization/ASTReader.cpp

@@ -106,6 +106,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/DJB.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -870,7 +871,7 @@ ASTSelectorLookupTrait::ReadData(Selector, const unsigned char* d,
 }
 
 unsigned ASTIdentifierLookupTraitBase::ComputeHash(const internal_key_type& a) {
-  return llvm::HashString(a);
+  return llvm::djbHash(a);
 }
 
 std::pair<unsigned, unsigned>
@@ -3226,7 +3227,7 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         PP.getPreprocessingRecord()->SetExternalSource(*this);
       F.BasePreprocessedSkippedRangeID = PP.getPreprocessingRecord()
           ->allocateSkippedRanges(F.NumPreprocessedSkippedRanges);
-      
+
       if (F.NumPreprocessedSkippedRanges > 0)
         GlobalSkippedRangeMap.insert(
             std::make_pair(F.BasePreprocessedSkippedRangeID, &F));