[turbofan] Implemented the optional Float32RoundDown operator.

src/ia32/assembler-ia32.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 971 matching lines @@
   void xorpd(XMMRegister dst, XMMRegister src);
   void sqrtsd(XMMRegister dst, XMMRegister src) { sqrtsd(dst, Operand(src)); }
   void sqrtsd(XMMRegister dst, const Operand& src);
 
   void andpd(XMMRegister dst, XMMRegister src);
   void orpd(XMMRegister dst, XMMRegister src);
 
   void ucomisd(XMMRegister dst, XMMRegister src) { ucomisd(dst, Operand(src)); }
   void ucomisd(XMMRegister dst, const Operand& src);
 
+  void roundss(XMMRegister dst, XMMRegister src, RoundingMode mode);
   void roundsd(XMMRegister dst, XMMRegister src, RoundingMode mode);
 
   void movmskpd(Register dst, XMMRegister src);
   void movmskps(Register dst, XMMRegister src);
 
   void cmpltsd(XMMRegister dst, XMMRegister src);
   void pcmpeqd(XMMRegister dst, XMMRegister src);
 
   void punpckldq(XMMRegister dst, XMMRegister src);
   void punpckhdq(XMMRegister dst, XMMRegister src);
@@ skipping 564 matching lines @@
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_IA32_ASSEMBLER_IA32_H_