Add roundsd instruction to ia32 and use it in optimized Math.floor.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 8916)
+++ src/hydrogen-instructions.h	(working copy)
@@ -2449,6 +2449,8 @@
     return Representation::Integer32();
   }
 
+  virtual void PrintDataTo(StringStream* stream);
+
   HValue* index() { return OperandAt(0); }
   HValue* length() { return OperandAt(1); }
 
@@ -3416,6 +3418,8 @@
     return Representation::Tagged();
   }
 
+  virtual void PrintDataTo(StringStream* stream);
+
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedFieldPolymorphic)
 
   static const int kMaxLoadPolymorphism = 4;
@@ -3449,6 +3453,8 @@
     return Representation::Tagged();
   }
 
+  virtual void PrintDataTo(StringStream* stream);
+
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedGeneric)
 
  private: