Use equals() in equals(StringData, StringData)

Equals is faster in a few ways.
(1) no call to memcmp unless string sizes are the same
(2) does a fast check for either of the strings being static
    before any calls to is_numeric_string

hphp/runtime/base/comparisons.h

@@ -390,7 +390,7 @@ inline bool equal(const StringData *v1, const StringData *v2) {
   if (v1 == v2) return true;
   if (v1 == nullptr) return v2->empty();
   if (v2 == nullptr) return v1->empty();
-  return v1->compare(v2) == 0;
+  return v1->equal(v2);
 }
 inline bool equal(const StringData *v1, CStrRef v2) {
   return equal(v1, v2.get());

hphp/runtime/base/string_data.cpp

@@ -855,6 +855,23 @@ DataType StringData::toNumeric(int64_t &lval, double &dval) const {
 ///////////////////////////////////////////////////////////////////////////////
 // comparisons
 
+HOT_FUNC
+bool StringData::equal(const StringData *s) const {
+  assert(s);
+  if (s == this) return true;
+  int ret;
+
+  if (!(m_hash < 0 || s->m_hash < 0)) {
+    ret = numericCompare(s);
+    if (ret >= -1) {
+      return ret == 0;
+    }
+  }
+  if (m_len != s->m_len) return false;
+  ret = memcmp(rawdata(), s->rawdata(), m_len);
+  return ret == 0;
+}
+
 HOT_FUNC
 int StringData::numericCompare(const StringData *v2) const {
   assert(v2);

hphp/runtime/base/string_data.h

@@ -322,21 +322,7 @@ public:
   /**
    * Comparisons.
    */
-  bool equal(const StringData *s) const {
-    assert(s);
-    if (s == this) return true;
-    int ret;
-
-    if (!(m_hash < 0 || s->m_hash < 0)) {
-      ret = numericCompare(s);
-      if (ret >= -1) {
-        return ret == 0;
-      }
-    }
-    if (m_len != s->m_len) return false;
-    ret = memcmp(rawdata(), s->rawdata(), m_len);
-    return ret == 0;
-  }
+  bool equal(const StringData *s) const;
 
   bool same(const StringData *s) const {
     assert(s);