Truncate rather than round to nearest when performing float-to-integer...

src/x64/disasm-x64.cc

 // Copyright 2009 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 1095 matching lines @@
       }
     } else if (opcode == 0x2A) {
       // CVTSI2SS: integer to XMM single conversion.
       int mod, regop, rm;
       get_modrm(*current, &mod, &regop, &rm);
       AppendToBuffer("%ss %s,", mnemonic, NameOfXMMRegister(regop));
       current += PrintRightOperand(current);
     } else if (opcode == 0x2C) {
       // CVTTSS2SI:
       // Convert with truncation scalar single-precision FP to dword integer.
-      // Assert that mod is not 3, so source is memory, not an XMM register.
-      ASSERT_NE(0xC0, *current & 0xC0);
-      current += PrintOperands("cvttss2si", REG_OPER_OP_ORDER, current);
+      int mod, regop, rm;
+      get_modrm(*current, &mod, &regop, &rm);
+      AppendToBuffer("cvttss2si%c %s,",
+          operand_size_code(), NameOfCPURegister(regop));
+      current += PrintRightXMMOperand(current);
     } else if (opcode == 0x5A) {
       // CVTSS2SD:
       // Convert scalar single-precision FP to scalar double-precision FP.
       int mod, regop, rm;
       get_modrm(*current, &mod, &regop, &rm);
       AppendToBuffer("cvtss2sd %s,", NameOfXMMRegister(regop));
       current += PrintRightXMMOperand(current);
     } else {
       UnimplementedInstruction();
     }
@@ skipping 583 matching lines @@
     for (int i = 6 - static_cast<int>(pc - prev_pc); i >= 0; i--) {
       fprintf(f, "  ");
     }
     fprintf(f, "  %s\n", buffer.start());
   }
 }
 
 }  // namespace disasm
 
 #endif  // V8_TARGET_ARCH_X64