shinezyy / co_2016_single_cycle

Installation of MIPS toolchain

First, Ubuntu 16.04 is expected (Or ubuntu 14.04). In my experience, for only LTS version mirror provide tool chain for other architectures.

sudo apt get update
sudo apt-cache search gcc-5-mips

Then you can get package list like the following:

gcc-5-mips-linux-gnu - GNU C compiler
gcc-5-mips-linux-gnu-base - GCC, the GNU Compiler Collection (base package)
gcc-5-mips64-linux-gnuabi64 - GNU C compiler
gcc-5-mips64-linux-gnuabi64-base - GCC, the GNU Compiler Collection (base package)
gcc-5-mips64el-linux-gnuabi64 - GNU C compiler
gcc-5-mips64el-linux-gnuabi64-base - GCC, the GNU Compiler Collection (base package)
gcc-5-mipsel-linux-gnu - GNU C compiler
gcc-5-mipsel-linux-gnu-base - GCC, the GNU Compiler Collection (base package)

The MIPS ISA we implemented is, of course, 32 bits, so mips64 should be ignores. Then the difference between mips and mipsel is that the latter one support little-endian only while the former one might support only big-endian or both. Your should install it according to the endian of your CPU.

Clone memory generation tool

https://github.com/jackyangNJ/testbench4mips.git

This is a tool designed by Yang Jie, the TA of CO-2015, which convert C and assembly code into memory initiating files. Its usage is decribed in README.md of that repo.

Note that

• You need not to download mips-gcc(This repo's README tell you to do that, but it is not needed anymore), because mirror of ubuntu provides it.
• the CROSS_COMPILE defined in the Makefile might not be the same as your tool-chain's prefix. You need to soft link your tool-chain to satisfy the Makefile, or modify this variable in Makefile to satisfy your tool-chain.

How to soft link?

cd /usr/bin
ls arm*

arm2hpdl                     arm-linux-gnueabi-gcc-4.7         arm-linux-gnueabi-ld.gold
arm-linux-gnueabi-addr2line  arm-linux-gnueabi-gcc-ar-4.7      arm-linux-gnueabi-nm
arm-linux-gnueabi-ar         arm-linux-gnueabi-gcc-nm-4.7      arm-linux-gnueabi-objcopy
arm-linux-gnueabi-as         arm-linux-gnueabi-gcc-ranlib-4.7  arm-linux-gnueabi-objdump

If your build system likes them to be arm-linux-gnu-gcc instead of arm-linux-gnueabi-gcc-4.7, you can run:

sudo ln -s arm-linux-gnueabi-gcc-4.7 arm-linux-gnu-gcc

Use it to build memory init file

This repo ships an example of assembly code for you, in start.S. Just make, then the following warnings might be encountered:

tart.S: Assembler messages:
start.S:34: Warning: macro instruction expanded into multiple instructions in a branch delay slot
start.S:39: Warning: macro instruction expanded into multiple instructions in a branch delay slot
start.S:67: Warning: macro instruction expanded into multiple instructions in a branch delay slot
start.S:90: Warning: macro instruction expanded into multiple instructions in a branch delay slot

What's it?

li instruction is a macro instruction, it will be translated into 1 or 2 instructions depend on the width of the immediate number.

Open start.S, around line 28, bne is followed by li. And the immediate number in li is bigger that 2^16-1, so li is translated into lui and or. Then lui is put in the delay slot of bne, and gcc found this is not logic: programmer might want an li in delay slot, which cannot be implemented. So it warns you.

In fact, this is not what you mean: we need nothing in a delay slot! Then, what should we do?

1. Add nops after every jump and branch
2. Compile C codes instead of using the shipped start.S