a2sm

What you need to know

Usage

First, you'll need execute permissions on the script itself. cd to the directory with the script, and run chmod +x a2sm.sh

C code is not directly handled by a2sm, but instead it reads the x86 assembly (intel syntax) that gcc generates from C files. In order to get this assembly, you run the following command: gcc -S -masm=intel my-code.c Which will produce a file named my-code.s in the same directory. Now you're ready to translate it!

The script takes the filename to read from as the only argument, and writes the translated assembly to stdout. So to capture it into a file of its own, simply redirect the output like so: ./a2sm.sh my-code.s > sm213-out.s And if you're lucky, all will have gone well. Due to the fact that a2sm is entirely pattern matching, most things will cause it to produce incorrect assembly without any warning. Check out the next section for what to not do.

What to Avoid...

• Don't use anything in C that doesn't translate right into SM213 assembly! This is the general rule.
• At the moment, do not use local variables as I have not bothered to see if I can transform them out to global status. This will take more than simple text replacement I think.
• The only supported datatypes are ints and longs and pointers to them.
• The only supported arithmetic so far is: addition, bitwise and, bitwise not, bitwise or, shift left/right. I'll soon simulate subtraction. No xor, multiplication, division, or modulo is available.
• Do not use any functions besides int main(). Not only does a2sm mark the first function defined as the entry point, but we don't have any call or jmp instructions in SM213 anyways (yet).
• Conditional statements are not supported because they require things like cmp/test and jmp (and its related instructions) which we do not have in SM213 yet.
• Bit-shifting by a variable number of bits (ie x = x << y;) is not supported because we can only shift in SM213 by a constant number of bits. I could get around this later when we have looping capabilities, but not yet.

Newest Changes

• I've posted an example C file and the generated SM213 code. You can look at it here
• You can now assign to global variables as you're declaring them.
• Using variable indices (ie. b[i] = 3) is now supported.

The Future?

• I don't think local variables will ever be supported due to how they are stack-allocated by GCC, and referenced by offsets from ebp...
• We have begun to discuss jumping and branching (/relative jumps). As this is a slightly different model than x86 uses (everything is a jmp of some conditional variant thereof, and there are special registers assigned for comparisons), I hope to be able to successfully port this across too. It's kinda crucial.