Garter Assembler

gasm is the intermediate language and assembly language of the garter compiler toolchain. The gasm assembly syntax is intended to be platform-agnostic wherever possible.

Usage

the Garter Assembler takes in *.gasm files and generates *.gyb object files.

Implementation

Lexical analysis breaks apart the source files into tokens: keywords, labels/addresses, constants, et cetera. Then the parser iterates over the list of tokens and essentially "interprets" them -- instructions will either change the assembler's internal state, or be translated and treated as emitter commands.

How does Object Emission Work?

When the assembler first starts, it initializes an empty object with a clean-slate symbol table. Any time we encounter symbol definitions, we push those to our symbol table.

Later, somewhere in our *.gasm file, we might see a block of code that looks like

section executable
    move rax, rax

section executable is a directive that changes what section the emitter is currently sending data into, then the instruction move rax, rax will be converted into data and put into the selected section.

GASM Assembly

gasm is heavily influenced by x86 Intel Assembly, FlatAssembler, BASIC, and Python, and looks something like:

section writeable
    hello
    u8 "Hello, World" 0
section executable
    immediate ar hello
    immediate br 12
    syscall write stdout ar br
    immediate 0
    syscall exit ar

For tutorials, see the garter website. For a guide on writing Garter Assembly, see the garter specification doc.