Collect both arguments for math's min/max static functions. Later that information will be used to …

runtime/vm/constants_x64.h

Index: runtime/vm/constants_x64.h
===================================================================
--- runtime/vm/constants_x64.h	(revision 25162)
+++ runtime/vm/constants_x64.h	(working copy)
@@ -90,6 +90,8 @@
 const Register SPREG = RSP;  // Stack pointer register.
 const Register FPREG = RBP;  // Frame pointer register.
 
+const Register ICREG = RBX;  // IC data register.
+
 // Exception object is passed in this register to the catch handlers when an
 // exception is thrown.
 const Register kExceptionObjectReg = RAX;