Make the RegExp.prototype object be a RegExp object.

src/regexp.js

Index: src/regexp.js
diff --git a/src/regexp.js b/src/regexp.js
index 38d4496153909f41d98ada01cd18ee5fa367fe63..0ab86f3338445e1394649f5e0597c2b1fb1cb8c2 100644
--- a/src/regexp.js
+++ b/src/regexp.js
@@ -95,12 +95,11 @@ function RegExpConstructor(pattern, flags) {
   }
 }
 
-
 // Deprecated RegExp.prototype.compile method.  We behave like the constructor
 // were called again.  In SpiderMonkey, this method returns the regexp object.
 // In JSC, it returns undefined.  For compatibility with JSC, we match their
 // behavior.
-function CompileRegExp(pattern, flags) {
+function RegExpCompile(pattern, flags) {
   // Both JSC and SpiderMonkey treat a missing pattern argument as the
   // empty subject string, and an actual undefined value passed as the
   // pattern as the string 'undefined'.  Note that JSC is inconsistent
@@ -108,6 +107,11 @@ function CompileRegExp(pattern, flags) {
   // RegExp.prototype.compile and in the constructor, where they are
   // the empty string.  For compatibility with JSC, we match their
   // behavior.
+  if (this == $RegExp.prototype) {
+    // We don't allow recompiling RegExp.prototype.
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['RegExp.prototype.compile', this]);
+  }
   if (IS_UNDEFINED(pattern) && %_ArgumentsLength() != 0) {
     DoConstructRegExp(this, 'undefined', flags);
   } else {
@@ -408,7 +412,6 @@ var lastMatchInfoOverride = null;
 function SetUpRegExp() {
   %CheckIsBootstrapping();
   %FunctionSetInstanceClassName($RegExp, 'RegExp');
-  %FunctionSetPrototype($RegExp, new $Object());
   %SetProperty($RegExp.prototype, 'constructor', $RegExp, DONT_ENUM);
   %SetCode($RegExp, RegExpConstructor);
 
@@ -416,7 +419,7 @@ function SetUpRegExp() {
     "exec", RegExpExec,
     "test", RegExpTest,
     "toString", RegExpToString,
-    "compile", CompileRegExp
+    "compile", RegExpCompile
   ));
 
   // The length of compile is 1 in SpiderMonkey.