How about using a MIPS Macro Assembler program. That's typically what would be used to convert an assembly language program to the equivalent machine code.
It's pretty obvious MAAASD that you are a high level software type that wants to dabble in FPGAs (because VHDL/Verilog is "code").
MAAASD, FYI, FPGAs are not software, VHDL/Verilog is not software. FPGAs are hardware with a design entry method that masquerades as software. You have to look at FPGA design as hardware design. Hence the reason so many here tout drawing a block diagram of the design before writing one line of "code". MAAASD learn how hardware works (learn about HW registers, combinatorial logic, setup/hold time, clocks, race conditions, metastability, sequential circuits, signaling standards, etc). Once you understand the difference between HW and SW, you'll have a starting point from which you can begin you first FPGA design.
Regards,
-alan