Improves performance for calls from Crankshaft code to certain string and...

src/regexp.js

Index: src/regexp.js
===================================================================
--- src/regexp.js	(revision 12582)
+++ src/regexp.js	(working copy)
@@ -206,6 +206,47 @@
 }
 
 
+function RegExpExecNoResult(string) {
+  if (!IS_REGEXP(this)) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['RegExp.prototype.exec', this]);
+  }
+
+  if (%_ArgumentsLength() === 0) {
+    var regExpInput = LAST_INPUT(lastMatchInfo);
+    if (IS_UNDEFINED(regExpInput)) {
+      throw MakeError('no_input_to_regexp', [this]);
+    }
+    string = regExpInput;
+  }
+  string = TO_STRING_INLINE(string);
+  var lastIndex = this.lastIndex;
+
+  // Conversion is required by the ES5 specification (RegExp.prototype.exec
+  // algorithm, step 5) even if the value is discarded for non-global RegExps.
+  var i = TO_INTEGER(lastIndex);
+
+  var global = this.global;
+  if (global) {
+    if (i < 0 || i > string.length) {
+      this.lastIndex = 0;
+      return null;
+    }
+  } else {
+    i = 0;
+  }
+
+  %_Log('regexp', 'regexp-exec,%0r,%1S,%2i', [this, string, lastIndex]);
+  // matchIndices is either null or the lastMatchInfo array.
+  var matchIndices = %_RegExpExec(this, string, i, lastMatchInfo);
+
+  if (matchIndices === null) {
+    if (global) this.lastIndex = 0;
+    return null;
+  }
+}
+
+
 // One-element cache for the simplified test regexp.
 var regexp_key;
 var regexp_val;