64位NASM师IDIV [英] 64bit nasm division idiv

问题描述

;print out division message
mov rcx, 0                       ;zero out register
mov rax, [input]
mov rcx, [input2]
idiv rcx                        ;divide rax by rcx
mov rdi, rax                    ;for printing purposes
call print_int

我似乎无法弄清楚这是为什么不分裂，我得到一个enrror浮点异常我使用的是64位机和值不整数浮点....想法？

I can't seem to figure out why this isn't dividing, I'm getting a enrror "Floating Point Exception" I'm using a 64bit machine and the values are integers not floating point.... ideas?

我知道发生分裂后，放置商应在RAX，其余应在RDX我相信，但截至现在，我只是试图让我的手在商。

I know after the division takes place the quotient should be in rax, and the remainder should be in rdx i believe, but as of right now i'm just trying to get my hands on the quotient.

推荐答案

您的功能看起来有点复杂，我。 IDIV 与该功能预计我在这里工作的：

Your function looks a little bit complicated to me. idiv works as expected for me here with this function:

_mydiv:
  xor  %rdx, %rdx ; clear high bits of dividend
  mov  %rdi, %rax ; copy dividend argument into rax
  idiv %rsi       ; divide by divisor argument
  ret             ; return (quotient is in rax)

翻译成NASM语法和窗户ABI，我想这会是这样的：

Translated into NASM syntax and to the windows ABI, I think that would be something like:

_mydiv:
  mov  r8, rdx    ; copy divisor argument to scratch register
  xor  rdx, rdx   ; clear high bits of dividend
  mov  rax, rcx   ; copy dividend argument into rax
  idiv r8         ; divide by divisor in scratch register
  ret             ; return (quotient is in rax)

您也许踩在你的参数和沿途混乱的东西吗？

Are you maybe stomping on your parameters and confusing something along the way?

编辑：看你的code，它发生，我认为它可能根本无法写成一个正常功能。最重要的步骤是：

looking at your code, it occurs to me that it might not be written as a proper function at all. The important steps are:

1. 把股息RDX：RAX - 你这可能意味着清理出RDX并把输入股息RAX


2. 把除数在其他一些寄存器 - 你选择RCX，这应该是罚款
。

3. 分割 - IDIV RCX


4. 结果将在RAX。

您应该特别注意步骤1 - 确保RDX：RAX有理智的内容！为什么你得到一个浮点例外，我无法从$ C $猜c您已经证明。

You should pay particular attention to step 1 - make sure that RDX:RAX has sane contents! Why you're getting a floating point exception I can't guess from the code you've shown.

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