Added roundss to the disassembler of x64 and ia32.

src/ia32/disasm-ia32.cc

Index: src/ia32/disasm-ia32.cc
diff --git a/src/ia32/disasm-ia32.cc b/src/ia32/disasm-ia32.cc
index 5a432806592f7c03903e66c99e629d8f87ab70f7..2f0fd0fc70ff54b5cb27320cc0a6b905b4264806 100644
--- a/src/ia32/disasm-ia32.cc
+++ b/src/ia32/disasm-ia32.cc
@@ -1630,7 +1630,15 @@ int DisassemblerIA32::InstructionDecode(v8::internal::Vector<char> out_buffer,
             }
           } else if (*data == 0x3A) {
             data++;
-            if (*data == 0x0B) {
+            if (*data == 0x0A) {
+              data++;
+              int mod, regop, rm;
+              get_modrm(*data, &mod, &regop, &rm);
+              int8_t imm8 = static_cast<int8_t>(data[1]);
+              AppendToBuffer("roundss %s,%s,%d", NameOfXMMRegister(regop),
+                             NameOfXMMRegister(rm), static_cast<int>(imm8));
+              data += 2;
+            } else if (*data == 0x0B) {
               data++;
               int mod, regop, rm;
               get_modrm(*data, &mod, &regop, &rm);