goren/skylang
1
1
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

Added more comments to the FASM codegen backend, to make it more readable.

Browse source
This commit is contained in:
Goren Barak 2023-11-23 21:47:25 -05:00
parent d83b651931
commit 1a6089b2a9
1 changed files with 26 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

30
src/codegen/fasm.rs
View file

@ -1,5 +1,16 @@
use crate::parse::ast::*;
macro_rules! fasm_codegen {
($exprs:expr) => {
fasm_codegen($exprs, false)
};
(function: $exprs:expr) => {
fasm_codegen($exprs, true)
}
}
pub fn fasm_codegen(exprs: &Vec<Expr>, not_a_function: bool) -> String {
// Define asm_func, used for functions.
let mut asm_func = String::new();
@ -130,19 +141,27 @@ pub fn fasm_codegen(exprs: &Vec<Expr>, not_a_function: bool) -> String {
asm_start.push_str("\tint3\n");
},
// Return something from a function.
Expr::Return(e) => {
asm_start.push_str(format!("mov [rbp - 8], {}", e.unwrap()).as_str());
// Move the return value to rbp + 8.
asm_start.push_str(format!("mov [rbp + 8], {}", e.unwrap()).as_str());
// [rbp + 8] ← return_value
},
// A function defenition.
Expr::FunDefinition(e) => {
// In x86-64 assembly, a function is defined as <function_name>:. Push this to the `asm_func`.
asm_func.push_str(format!("{}:\n", e.name).as_str());
asm_func.push_str(fasm_codegen(&e.contents, false).as_str());
// Call the function itself specifying that you are defining a function, and push the returned value to `asm_func`.
asm_func.push_str(fasm_codegen!(function: &e.contents).as_str());
// Use the ret instruction to return from the procedure.
asm_func.push_str("\tret\n");
},
_ => unsafe {
let mut ptr = 0x00 as *mut u32;
::std::ptr::write(ptr, "GOREN IS MY NAME AND BREAKING MEMORY IS MY GAME");
// Write some data I randomly typed to your memory because don't going around playing with something that I haven't implemented yet.
let mut ptr = 0x00 as *mut f64;
::std::ptr::write(ptr, 124010240120401240.12410240124120401240);
},
}
@ -150,10 +169,13 @@ pub fn fasm_codegen(exprs: &Vec<Expr>, not_a_function: bool) -> String {
if not_a_function {
// Use the exit syscall to leave the program. If you don't do this, you will get a segmentation fault.
asm_start.push_str("\tmov rax, 60 ; 60 is the system call number for exit.\n");
asm_start.push_str("\txor rdi, rdi ; 0 is the exit code we want.\n");
asm_start.push_str("\tsyscall ; this is the instruction to actually perform the system call.\n");
}
// Get the final `asm` string derived from all of the other strings that we have manipulated (finally!).
let asm = format!("{}{}{}", asm_start, asm_func, asm_data);
// Return the final `asm` string.
asm
}