Code Generation — শেষ ধাপে সিলিকনের ভাষায় অনুবাদ

Generator-টা এই লেসনের প্রতিটা নিয়ম প্রয়োগ করে:

import sys

ARG_REGS = ['%rdi', '%rsi', '%rdx', '%rcx', '%r8', '%r9']
BINOP = {'+': 'addq', '-': 'subq', '*': 'imulq'}

class CodeGen:
    def __init__(self, homes):
        self.homes = homes                      # {'a': '-8', ...} (rbp-relative)
        self.slots = len(homes)                 # সব value slot-এই থাকে
        self.out = []
        self.label_n = 0

    def home(self, v):
        if v.startswith('%'):                   # ইতিমধ্যে register
            return v
        return f"{self.homes[v]}(%rbp)"

    def get(self, v, reg='%rax'):
        """v-র মান reg-এ আনো"""
        self.emit(f"movq {self.home(v)}, {reg}")

    def put(self, v, reg='%rax'):
        """reg-এর মান v-তে জমা"""
        self.emit(f"movq {reg}, {self.home(v)}")

    def emit(self, line):
        self.out.append(f"    {line}")

    def label(self, text=None):
        name = text or f".L{self.label_n}"
        self.label_n += 1
        self.out.append(f"{name}:")
        return name

    def prologue(self):
        frame = ((self.slots * 8 + 15) // 16) * 16   # byte-এ align
        self.out += [f"    .text", f"    .globl main", f"main:",
                     f"    push %rbp", f"    mov %rsp, %rbp",
                     f"    sub ${frame}, %rsp"]

    def epilogue(self):
        self.out += [f"    mov %rbp, %rsp", f"    pop %rbp", f"    ret"]

    def gen_binop(self, dest, a, op, b):
        self.get(a, '%rax')
        if op == '/':
            self.emit("cqto")
            self.emit(f"idivq {self.home(b)}")
        else:
            rhs = f"${b}" if b.lstrip('-').isdigit() else self.home(b)
            self.emit(f"{BINOP[op]} {rhs}, %rax")
        self.put(dest)

    def gen_call(self, dest, fname, args):
        for i, a in enumerate(args[:len(ARG_REGS)]):
            self.get(a, ARG_REGS[i])
        self.emit(f"call {fname}")
        if dest:
            self.put(dest)

    def generate(self, tac_lines):
        self.prologue()
        for line in tac_lines:
            line = line.strip()
            if not line:
                continue
            if line.endswith(':'):
                self.label(line.rstrip(':') or None)
            elif line.startswith('goto'):
                self.emit(f"jmp {line.split()[1]}")
            elif line.startswith('if'):
                # রূপ: if x OP y goto L
                _, x, op, y, _, lbl = line.split()
                self.get(x, '%rax')
                rhs = f"${y}" if y.isdigit() else self.home(y)
                self.emit(f"cmpq {rhs}, %rax")
                mnem = {'<': 'jl', '>': 'jg', '<=': 'jle',
                        '>=': 'jge', '==': 'je', '!=': 'jne'}[op]
                self.emit(mnem + ' ' + lbl)
            elif line.startswith('ret'):
                self.get(line.split()[1], '%rax')
                self.epilogue()
            elif '=' in line:
                dest, expr = [s.strip() for s in line.split('=', 1)]
                parts = expr.split()
                if len(parts) == 1:             # copy: d = x
                    src = parts[0]
                    if src.lstrip('-').isdigit():
                        self.emit(f"movq ${src}, %rax")
                    else:
                        self.get(src)
                    self.put(dest)
                elif parts[1] == 'CALL':
                    self.gen_call(dest, parts[2], parts[3:])
                else:
                    self.gen_binop(dest, parts[0], parts[1], parts[2])
        return "\n".join(self.out) + "\n"


tac = """
    t0 = 6
    a  = t0
    t1 = 7
    b  = t1
    t2 = a * b
    t3 = t2 + 2
    c  = t3
    if c <= 40 goto L_else
    t4 = c - 4
    c  = t4
L_else:
    ret c
"""

homes = {'t0': '-32', 't1': '-40', 't2': '-48',
         't3': '-56', 't4': '-64',
         'a': '-8',  'b': '-16', 'c': '-24'}

print(CodeGen(homes).generate(tac.splitlines()))

চালান ও যাচাই করুন:

python3 codegen.py > gen.s
gcc gen.s -o gen && ./gen; echo "exit=$?"

প্রত্যাশিত output:

exit=40

(macOS-এ _main rename করতে ভুলবেন না।) উপরের example section-এর hand-written .s-এর সাথে generator-ের output পাশাপাশি রাখুন — একই logic-এর দুই উপস্থাপনা।

নিজে বাড়ান:

1. Division (cqto/idivq template তৈরিই আছে) — 17 / 5 emit করে exit code 3 যাচাই করুন
2. print builtin — .rodata literal pool + printf call (variadic-এ %al = 0 কেন দরকার, ভাবুন)
3. “সব value slot-এ” নীতি ভেঙে hot value register-এ আনুন — call-boundary spill ছাড়া কোথায় ভাঙে, test লিখুন