single_pass_compiler.py

"""
Followed tutorial from:
https://keleshev.com/one-pass-compiler-primer

python .\calc_compiler.py 1 + 2; bat calc.s; zig cc -Wno-everything calc.s -o calc.exe; ./calc.exe; Write-Host $LASTEXITCODE

The Program:
    1 + 2 + 3 * 4

Will Be Compiled To:
    .global main
    main:
	push $1
	push $2
	pop %rax
	pop %rbx
	add %rbx, %rax
	push %rax
	push $3
	pop %rax
    	pop %rbx
    	add %rbx, %rax
    	push %rax
    	push $4
    	pop %rax
    	pop %rbx
    	mul %rbx
    	push %rax
    	pop %rax
    	ret
"""
import sys

def gen(tokens, out=sys.stdout):
    emit = out.write
    emit('.global main\n')
    emit('main:\n')
    for token in tokens:
        if isinstance(token, int):
            emit(f'\tpush ${token}\n')
        elif 'ADD' in token:
            emit('\tpop %rax\n')
            emit('\tpop %rbx\n')
            emit('\tadd %rbx, %rax\n')
            emit('\tpush %rax\n')
        elif 'MUL' in token:
            emit('\tpop %rax\n')
            emit('\tpop %rbx\n')
            emit('\tmul %rbx\n')
            emit('\tpush %rax\n')
    emit('\tpop %rax\n')
    emit('\tret\n')
    
def lex(text):
    for t in text.split():
        if t.isnumeric():
            yield int(t)
        else:
            yield 'OP_' + {'+' : 'ADD', '*' : 'MUL'}[t]
            
def parse(tokens):
    yield next(tokens)
    for b in tokens:
        op = next(tokens)
        yield op
        yield b
        

def compile(text, out=sys.stdout):
    gen(parse(lex(text)), out)

    
if __name__ == '__main__':
    with open('calc.s', 'w') as outfile:
        compile(' '.join(sys.argv[1:]), outfile)