How to Execute Mips Assembly Programs on an X86 Linux

How can I execute MIPS assembly programs on an x86 linux?

You will need either a cross compilation toolchain, or to build your own cross binutils.
For a prebuilt toolchain, you can visit code sourcery. If you just want to compile assembly, then all
you need is binutils. There are some guidelines on the Linux Mips wiki

For the emulation part, QEmu would be my choice.

How to Debug MIPS elf?

If you are in possession of a hardware with MIPS CPU that can run Linux, the easiest way would be to use one of the Linux distributions for MIPS architecture. A common one is Debian distribution, and you can find more about Debian for MIPS at this link.

If you do not have access to MIPS hardware, running QEMU on your x86 host should be sufficient. Take a look at MIPS-QEMU instructions.

Last, once you have MIPS Linux in place, copy your MIPS binary to it, log in, and run gdb with it. This should give you a solid environment to debug it. Speaking of understanding MIPS assembly, the architecture is clean and simple, and it is much easier to read MIPS assembly than other arch's assembly code.

Running MIPS instructions on a real machine [not on simulator]

Is it possible to create an executable file from MIPS instructions?

Yes, because an assembler is just a program that reads some input and produce some output files, therefore you can assemble for any architectures from any other architectures, in the same way as the possibility to cross-compile for other architectures from your PC

But executing the output file is an entirely different thing. Each architecture has its own machine language. Just like how humans can't understand people speaking other languages, machines only understand programs written in its language. That means MIPS hardware can only understand and run MIPS binaries. Other architectures like x86 can't interpret another instruction set with different instruction coding

So the only way for you is to use an emulator or simulator

Create a Fully-Featured Environment For MIPS Assembly Development

spim seems to be the classic MIPS simulator.

How to assemble for MIPS cpu in the gnu assembler

Do you have a version of GNU Binutils built to target MIPS? It's not like clang where you can use clang -target mips -march=mips1 -c foo.s && llvm-objdump -d foo.o (MIPS1 includes R2000 and R3000).

For example, to run GAS for ARM on my x86-64 desktop, I can run arm-none-eabi-as since I installed the arm-none-eabi-binutils package on my Arch Linux system. You'd need something similar, or configure and build Binutils from source yourself, to get a mips-something-something-as executable you could run.

Just plain as (/usr/bin/as) will be a native assembler for your system, so x86-64 if you're on x86-64, with no support for other ISAs. (Except for i386 with as --32 because Binutils considers amd64 and i386 as different versions of the same ISA).

Loongson CPU and MIPS Assembly?

Loongson 2F is MIPS III-compatible, so this means that you will be able to write MIPS III compatible assembly, compile it and run it. If available, native toolchain should be a better choice than any cross toolchain.

I would suggest reading a UserGuide which will tell you what instructions you have available. Note that the instruction set for this chip has been extended with number of different integer/fp/media instructions.