Optimize StringImpl::find when searching for patterns with length > 1

third_party/WebKit/Source/wtf/text/StringImpl.cpp

Index: third_party/WebKit/Source/wtf/text/StringImpl.cpp
diff --git a/third_party/WebKit/Source/wtf/text/StringImpl.cpp b/third_party/WebKit/Source/wtf/text/StringImpl.cpp
index e7004b9244bd8d3feaf910f8135488ca4c93a090..b1b14798ee8d937110cc3a550066b33d833cba93 100644
--- a/third_party/WebKit/Source/wtf/text/StringImpl.cpp
+++ b/third_party/WebKit/Source/wtf/text/StringImpl.cpp
@@ -1246,15 +1246,26 @@ ALWAYS_INLINE static size_t findInternal(const SearchCharacterType* searchCharac
     // delta is the number of additional times to test; delta == 0 means test only once.
     unsigned delta = searchLength - matchLength;
 
+    // Find on a single character is very fast, so first do that to figure out
+    // where to start.
+    size_t start = WTF::find(searchCharacters, searchLength, matchCharacters[0]);
+    if (start == kNotFound || start > delta)
+        return kNotFound;
+
+    // TODO(esprehn): Consider using Boyer-Moore-Horspool or a hybrid approach
+    // like v8/src/string-search.h, also investigate the badness factor used
+    // by v8 where they use single char find() repeatedly until they think
+    // it's too costly then switch to Boyer-Moore-Horspool.
+
     unsigned searchHash = 0;
     unsigned matchHash = 0;
 
     for (unsigned i = 0; i < matchLength; ++i) {
-        searchHash += searchCharacters[i];
+        searchHash += searchCharacters[start + i];
         matchHash += matchCharacters[i];
     }
 
-    unsigned i = 0;
+    unsigned i = start;
     // keep looping until we match
     while (searchHash != matchHash || !equal(searchCharacters + i, matchCharacters, matchLength)) {
         if (i == delta)