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

src/ia32/disasm-ia32.cc

 // Copyright 2011 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1123 matching lines @@
               data++;
               int mod, regop, rm;
               get_modrm(*data, &mod, &regop, &rm);
               AppendToBuffer("movntdqa %s,", NameOfXMMRegister(regop));
               data += PrintRightOperand(data);
             } else {
               UnimplementedInstruction();
             }
           } else if (*data == 0x3A) {
             data++;
-            if (*data == 0x16) {
+            if (*data == 0x0B) {
+              data++;
+              int mod, regop, rm;
+              get_modrm(*data, &mod, &regop, &rm);
+              int8_t imm8 = static_cast<int8_t>(data[1]);
+              AppendToBuffer("roundsd %s,%s,%d",
+                             NameOfXMMRegister(regop),
+                             NameOfXMMRegister(rm),
+                             static_cast<int>(imm8));
+              data += 2;
+            } else if (*data == 0x16) {
               data++;
               int mod, regop, rm;
               get_modrm(*data, &mod, &regop, &rm);
               int8_t imm8 = static_cast<int8_t>(data[1]);
               AppendToBuffer("pextrd %s,%s,%d",
                              NameOfCPURegister(regop),
                              NameOfXMMRegister(rm),
                              static_cast<int>(imm8));
               data += 2;
             } else if (*data == 0x22) {
@@ skipping 465 matching lines @@
       fprintf(f, "  ");
     }
     fprintf(f, "  %s\n", buffer.start());
   }
 }
 
 
 }  // namespace disasm
 
 #endif  // V8_TARGET_ARCH_IA32