Optimization of single character indexOf. Gives small improvement on GCC4.2,...

Optimization of single character indexOf. Gives small improvement on GCC4.2, but large improvement on GCC 4.3 (which was much worse on that particular code).


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@887 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/runtime.cc

@@ -1241,11 +1241,8 @@ static int BoyerMooreIndexOf(Vector<const schar> subject,
 
 template <typename schar>
 static int SingleCharIndexOf(Vector<const schar> string,
-                             uc16 pattern_char,
+                             schar pattern_char,
                              int start_index) {
-  if (sizeof(schar) == 1 && pattern_char > String::kMaxAsciiCharCode) {
-    return -1;
-  }
   for (int i = start_index, n = string.length(); i < n; i++) {
     if (pattern_char == string[i]) {
       return i;
@@ -1380,9 +1377,19 @@ int Runtime::StringMatch(Handle<String> sub,
   if (pattern_length == 1) {
     AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid
     if (sub_shape.IsAsciiRepresentation()) {
-      return SingleCharIndexOf(sub->ToAsciiVector(),
-                               pat->Get(pat_shape, 0),
-                               start_index);
+      uc16 pchar = pat->Get(pat_shape, 0);
+      if (pchar > String::kMaxAsciiCharCode) {
+        return -1;
+      }
+      Vector<const char> ascii_vector =
+        sub->ToAsciiVector().SubVector(start_index, subject_length);
+      void* pos = memchr(ascii_vector.start(),
+                         static_cast<const char>(pchar),
+                         static_cast<size_t>(ascii_vector.length()));
+      if (pos == NULL) {
+        return -1;
+      }
+      return reinterpret_cast<char*>(pos) - ascii_vector.start() + start_index;
     }
     return SingleCharIndexOf(sub->ToUC16Vector(),
                              pat->Get(pat_shape, 0),