codegen.c

#include "9cc.h"

Node *new_node(NodeKind kind) {
  Node *node = calloc(1, sizeof(Node));
  node->kind = kind;
  return node;
}

Node *new_binary(NodeKind kind, Node *lhs, Node *rhs) {
  Node *node = new_node(kind);
  node->lhs = lhs;
  node->rhs = rhs;
  return node;
}

Node *new_node_num(int val) {
  Node *node = calloc(1, sizeof(Node));
  node->kind = ND_NUM;
  node->val = val;
  return node;
}

// expr       = equality
// equality   = relational ("==" relational | "!=" relational)*
// relational = add ("<" add | "<=" add | ">" add | ">=" add)*
// add        = mul ("+" mul | "-" mul)*
// mul        = unary ("*" unary | "/" unary)*
// unary      = ("+" | "-")? primary
// primary    = num | "(" expr ")"

Node *expr() {
  return equality();
}

Node *equality() {
  Node *node = relational();

  for(;;) {
    if(consume("=="))
      node = new_binary(ND_EQ, node, relational());
    else if(consume("!="))
      node = new_binary(ND_NE, node, relational());
    else
      return node;
  }
}

Node *relational() {
  Node *node = add();

  for(;;) {
    if(consume("<"))
      node = new_binary(ND_LT, node, add());
    else if(consume("<="))
      node = new_binary(ND_LE, node, add());
    else if(consume(">"))
      node = new_binary(ND_LT, add(), node);
    else if(consume(">="))
      node = new_binary(ND_LE, add(), node);
    else
      return node;
  }
}

Node *add() {
  Node *node = mul();
  for(;;) {
    if(consume("+"))
      node = new_binary(ND_ADD, node, mul());
    else if(consume("-"))
      node = new_binary(ND_SUB, node, mul());
    else
      return node;
  }
}

Node *mul() {
  Node *node = unary();

  for(;;) {
    if(consume("*"))
      node = new_binary(ND_MUL, node, unary());
    else if(consume("/"))
      node = new_binary(ND_DIV, node, unary());
    else
      return node;
  }
}

Node *unary() {
  if(consume("+"))
    return primary();
  if(consume("-"))
    return new_binary(ND_SUB, new_node_num(0), primary());
  return primary();
}

Node *primary() {
  // 次のトークンが"("なら、"(" expr ")"のはず
  if(consume("(")) {
    Node *node = expr();
    expect(")");
    return node;
  }

  // そうでなければ数値のはず
  return new_node_num((expect_number()));
}

void gen(Node *node) {
  if(node->kind == ND_NUM) {
    printf("  push %d\n", node->val);
    return;
  }

  gen(node->lhs);
  gen(node->rhs);

  printf("  pop rdi\n");
  printf("  pop rax\n");

  switch(node->kind) {
    case ND_ADD:
      printf("  add rax, rdi\n");
      break;
    case ND_SUB:
      printf("  sub rax, rdi\n");
      break;
    case ND_MUL:
      printf("  imul rax, rdi\n");
      break;
    case ND_DIV:
      printf("  cqo\n");
      printf("  idiv rdi\n");
      break;
    case ND_EQ:
      printf("  cmp rax, rdi\n");
      printf("  sete al\n");
      printf("  movzb rax, al\n");
      break;
    case ND_NE:
      printf("  cmp rax, rdi\n");
      printf("  setne al\n");
      printf("  movzb rax, al\n");
      break;
    case ND_LE:
      printf("  cmp rax, rdi\n");
      printf("  setle al\n");
      printf("  movzb rax, al\n");
      break;
    case ND_LT:
      printf("  cmp rax, rdi\n");
      printf("  setl al\n");
      printf("  movzb rax, al\n");
      break;
  }

  printf("  push rax\n");
}