如何将这段汇编代码翻译成c? [英] How this assembly code will be translated into c?

问题描述

在 C 中，我有以下结构:

In C I have the following struct:

typedef struct _Node{
    int data;
    struct _Node *left;
    struct _Node *right;
} Node;

以及以下汇编代码:

.section .text
.global _start

_start:
    mov $8, %esi
    mov $A, %rdi
    call func
    movq $60, %rax
    movq $0, %rdi
    syscall
    
func:
    pushq %rbp
    movq %rsp, %rbp
    cmp (%rdi), %esi
    jne continue
    mov $1, %eax
    jmp finish
    
continue:
    cmpq $0, 4(%rdi)
    je next
    pushq %rdi
    mov 4(%rdi), %rdi
    call func
    pop %rdi
    cmp $1, %eax
    je finish

next:
    cmpq $0, 12(%rdi)
    je fail
    pushq %rid
    mov 12(%rdi), %rdi
    call func
    pop %rdi
    cmp $1, %eax
    je finish
   
fail:
    mov $0, %rax

finish:
    leave
    ret

现在尝试用 C 编写它，我有一个问题:

Now trying to write it in C I have a question:

__long__ func ( Node *root, __int__ x){
            if (root->data == __x__ )
                return 1;

            if (root->left != null)
               if (_____??_____)
                   return ___ func(root->left, x)____;

            if (root->right != null)
                return ____func(root->right, x)____;
}

为什么我们有 2 个 if-if ?如果 left 不为 null，则汇编代码会使用左子调用该函数，并且不会进行其他条件检查(即 cmp 调用).

Why we have 2 if-if inside each other? If left isn't null the assembly code calls the function with the left son and doesn't do another condition check (ie cmp call).

推荐答案

第二个 if 是如果 func 成功则返回的那个.

The second if is the one that returns if func was successfull.

bool func(Node *nd, int x)
{
    if (nd->data == x)
        return true;

    if (nd->left)
    {
        if (func(nd->left, x) == true)
            return true;
    }

    if (nd->right)
        return func(nd->right, x);
    
    return false;
}

我选择 bool 因为它在这个函数的上下文中是有意义的，即使 int 或 long 或其他也可能是有效的.

I choose bool because it makes sense in the context of this function, even though int or long or others may also be valid.

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