Replace HashString algorithm with xxHash64

The previous algorithm processed one character at a time, which is very
painful on a modern CPU. Replace it with xxHash64, which both already
exists in the codebase and is fairly fast.

Patch from Scott Smith!

Differential Revision: https://reviews.llvm.org/D32509

llvm-svn: 301487

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/Support/xxhash.cpp b/llvm/lib/Support/xxhash.cpp
index a7d990bf6a4..ca3120df4bc 100644
--- a/llvm/lib/Support/xxhash.cpp
+++ b/llvm/lib/Support/xxhash.cpp
@@ -68,9 +68,8 @@ static uint64_t mergeRound(uint64_t Acc, uint64_t Val) {
   return Acc;
 }
 
-uint64_t llvm::xxHash64(StringRef Data) {
+uint64_t llvm::xxHash64(StringRef Data, uint64_t Seed) {
   size_t Len = Data.size();
-  uint64_t Seed = 0;
   const char *P = Data.data();
   const char *const BEnd = P + Len;
   uint64_t H64;