Add a compare stub on ARM.

src/assembler.cc

Index: src/assembler.cc
===================================================================
--- src/assembler.cc	(revision 2284)
+++ src/assembler.cc	(working copy)
@@ -608,6 +608,12 @@
 }
 
 
+static int native_compare_doubles(double x, double y) {
+  if (x == y) return 0;
+  return x < y ? 1 : -1;
+}
+
+
 ExternalReference ExternalReference::double_fp_operation(
     Token::Value operation) {
   typedef double BinaryFPOperation(double x, double y);
@@ -630,6 +636,12 @@
 }
 
 
+ExternalReference ExternalReference::compare_doubles() {
+  return ExternalReference(Redirect(FUNCTION_ADDR(native_compare_doubles),
+                                    false));
+}
+
+
 ExternalReferenceRedirector* ExternalReference::redirector_ = NULL;