asm.lua

A Lua-based assembly-like language designed for learning and teaching assembly.

asm.lua based on the x86 architecture. To Lua, it's what asm.js is it to JavaScript, except that it's not actually faster. It compiles to pure Lua and is implemented in pure Lua.

It is currently in very early development. asm.lua is not yet guaranteed to work and many features are subject to change.

Examples

To compile the examples, execute ./asm.lua examples/X.lua, where X is any of the examples included in the examples directory. This will create a file called a.lua that can be ran using the Lua interpreter, like so: lua a.lua.

Short reference

Registers

• general purpose registers (can be used for any operation (mostly)) (only numbers allowed here)
  • A the accumulator
  • B base index
  • C counter
  • D arithmetic
• string registers (only strings are allowed here)
  • SS source string
  • DS destination string
• F flag register
  • f.gt greater than
  • f.lt less than
  • f.ge greater or equal to
  • f.le less or equal to
  • f.eq equal to
  • f.ne not equal to
  • f.err general purpose error flag
  • f.syserr system error flag
• SP stack pointer

Memory

Memory is divided into cells indexed by integers. Every cell holds a Lua variable (either a string or a number).

0

reserved for nil
cannot be changed

1ki .. 64ki

general purpose memory

64ki .. 80ki

stack

24ki video memory?

// TODO

Syntax & semantics

Operations

<op> [dst], [src] -- comment

Reference

• data moving
  • mov DST, SRC moves SRC to DST
• functions
  • call F calls F
  • callx F calls an extern F
  • ret returns from function
• stack
  • push SRC pushes SRC to stack
  • pop DST pops from stack to DST
• testing
  • cmp A, B compares A and B
  • test A tests if A is zero
  • not negates last comparison
• boolean
  • cmpl DST binary compliment
  • and DST, SRC binary and
  • or DST, SRC binary or
  • xor DST, SRC binary xor
  • nand DST, SRC binary nand
  • nor DST, SRC binary nor
  • xnor DST, SRC binary xnor
• arithmetic
  • inc DST increments DST
  • dec DST decrements DST
  • add DST, SRC adds SRC to DST
  • sub DST, SRC subtracts SRC from DST
  • mul DST, SRC multipies DST by src
  • div DST, SRC divides DST by SRC

Note

The bitwise operators require the Lua bitops library. It is currently not included by default, but is available by default when using LuaJIT.

Conditional

cmp <dst>, <src> OR test <dst>
if <cond> then
... code
end

cond can be gt, lt, ge, le, eq, ne, err or syserr

Loops

repeat
... code
 cmp <dst>, <src> OR test <dst>
until <cond>

cmp <dst>, <src> OR test <dst>
while <cond> do
... code
 cmp <dst>, <src> OR test <dst>
end

loop
... code
end

The last one loops as long as register C is not 0.

Functions

<name>:
... code
 ret
end

Lua ffi

extern <name>
mov <extern-dst>, <any-src>
callx <extern-func>, <n>