[Support] Replace HashString with djbHash.

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

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

https://reviews.llvm.org/D43615
(cherry picked from commit 77f7f965bc9499a9ae768a296ca5a1f7347d1d2c)

llvm-svn: 326081

1 files changed, 4 insertions, 4 deletions

diff --git a/clang/lib/Lex/PTHLexer.cpp b/clang/lib/Lex/PTHLexer.cpp
index d6c20a13d27..be6f6843a29 100644
--- a/clang/lib/Lex/PTHLexer.cpp
+++ b/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 @@ public:
   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 @@ public:
   }
 
   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.