NOT FOR COMMITTING: Add fast side-effect free floating point expressions.

src/ia32/codegen-ia32.h

Index: src/ia32/codegen-ia32.h
===================================================================
--- src/ia32/codegen-ia32.h	(revision 3987)
+++ src/ia32/codegen-ia32.h	(working copy)
@@ -419,6 +419,9 @@
   // temporarily while the code generator is being transformed.
   void LoadAndSpill(Expression* expression);
 
+  // Load an expression, trying the side-effect free compiler if possible.
+  void LoadPossiblySafeExpression(Expression* expression);
+
   // Read a value from a slot and leave it on top of the expression stack.
   Result LoadFromSlot(Slot* slot, TypeofState typeof_state);
   Result LoadFromSlotCheckForArguments(Slot* slot, TypeofState typeof_state);