LC2K+ is a C-like macro preprocessor for LC2K, the assembly language used for EECS370 at the University of Michigan. It adds basic C-like symbol and function style macro definition, line continuation, better labelling, and C/C++ style comments to the LC2K assembly language.
Writing assembly is hard. Writing LC2K is harder. LC2K+ makes it easier to write your LC2K assembly programs by allowing you to rename register, reduce code duplication, and most importantly, organize your code with indentation, multiline comments, and empty lines.
LC2K+ is written by a C programmer with the C language in mind. All language constructs added to the LC2K+ language are equivalent to those in the C language. If you're familiar with C/C++, you will instantly master LC2K+
LC2K+ converts an LC2K+ source file into a valid LC2K assembly file. Use
lc2k+.py <source file> <dest file>
where <source file> is the location of your LC2K+ code file, and <dest file> is the assembly file
to be generated. For example,
lc2k+.py comb.hras comb.as
Download lc2k+.py from https://raw.github.com/interarticle/lc2k-plus/master/lc2k+.py
You need to have Python 2.7 installed. Since most linux distributions come installed with python,
just open a terminal and type python --version to ensure you have Python 2.7 set as the default
python. If not, consult your distributions manuals for the installation of Python 2.7 and setting
it as the default python program.
Make sure lc2k+.py is executable through
chmod +x l2ck+.py
You can either copy lc2k+.py to /usr/local/bin, or put it under your working directory. In the second
case, invoke LC2K+ using
./lc2k+.py <source file> <dest file>
You must install Python 2.7 from http://www.python.org/download/. Please do not use Python 3.x.
After installation, you may simply open a Command Prompt (cmd.exe), then type
lc2k+.py <source file> <dest file>
under the folder you put lc2k+.py.
The language used by LC2K+ is mostly compatible with LC2K, except in label handling. Make sure you read the next section on labels before you start, or you will find surprising results.
In LC2K, labels are put as the first word on each line. Such a design makes it hard to write code without pounding on the space key. As such, the author has decided to drop compatibility with the LC2K label syntax.
Labels in LC2K+ are denoted by a colon (:), the same as in C/C++, in the form
label: instruction
As opposed to LC2K, you may start a line without any space/label, and it will be handled accordingly. For example,
add 0 0 1
label: add 0 0 1
Labels do not have to be on the same line as the instruction. Thus, the following is also legal:
label:
add 0 0 1
Finally, you may indent each line as you like:
main:
instruction
instruction
instruction
func1:
instruction
instruction
...
Bored of refering to registers using just numbers? Like the way you call registers r? in ARM? LC2K+ also supports
this way of refering to registers. You can call any register with a r prefix, for example,
add r0 r0 r1
Macros in LC2K+ are the same as macros in C/C++. Macros are defined using the #define preprocessor command.
Macro names may contain a-z, A-Z, 0-9, and symbols $ and _
Symbol-like macros are like constants. Any word in the LC2K+ source code that matches the name of the macro will be replaced by the value defined for the macro. For example:
#define NAME VALUE
After the definition, any mention of NAME will be replaced by VALUE.
For example, you may want to call r0 $zero. You would do
#define $zero r0
Then, you can do things like
lw $zero r7 addr
which is the same as writing lw r0 r7 addr
Function-like macros are like C functions. Function-like macros may have parameters, which will replace the corresponding values in the macro value. For example, (based on http://evanhahn.com/random/eecs-370-lc-2k-tricks/)
#define mov(src, dst) add r0 src dst
Then, you can copy the value from register 3 to register 2 using
mov(r2, r3)
WARNING: LC2K+ macros do NOT define new LC2K instructions. You must add a pair of parenthesis when instantiating a function-like macro.
To facilitate multiple commands in a macro, I added the feature to include multiple commands on the same
line. To do so, simply seperate the commands using semicolons (;). For example:
add r1 r2 r3; add r2 r3 r4
will be processed to
add r1 r2 r3
add r2 r3 r4
With this feature, you can write the following macros:
#define twonoops() noop; noop
WARNING: LC2K+ is still sensitive to line-breaks.
Just like in C, you may put multiple lines into a macro or instruction (hmm, can't think of why you'd need that)
with line continuation. To do line continuation, add a backslash (\) and the end of a line. For example,
#define twonoops() noop; \
noop
This is equivalent to
#define twonoops() noop; noop
Last but not least, you can add C and C++ style comments to your LC2K+ code. For example:
/*
@file something.hras
This is a block comment for the LC2K+ file!
*/
//And here's an inline comment
noop //This is a comment for noop
All comments are removed after processing. If you want to retain comment in the resulting LC2K file, please do it the LC2K way, i.e. by adding text directly after the instruction.
In addition to the disclaimer in the license, you should understand that
- This software is not required/necessary as part of any class projects in EECS370.
- The author does not guarantee the correctness of this software.
- The author should not be held responsible for any consequences caused by the use of this software, like losing points for an incorrectly generated LC2K assembly file, or failing to understand raw LC2K code in an exam due to excessive use of this software (unlikely).
Please, make sure you check the generated LC2K file before you submit it. Since this software was hacked out in a day, I cannot guarantee that it's bug-free.
Feel free to report any bugs you find using github. Or even better, fork the code and improve it yourself!
- Under Linux, you may rename
lc2k+.pytolc2k+, in order that you may invoke the program aslc2k+.
赵迤晨 (Zhao, Yichen) [email protected]