有人可以帮我找出以下程序有什么问题吗?我正在阅读“从头开始编程”并尝试将示例转换为 x86-64 程序集。下面的程序在一组数据中找到最大的数。但是当我组装、链接和运行它时,我得到 0。这显然不是最大的数字。它在 32 位寄存器/指令下运行良好,但不是 64 位。
# PURPOSE: This program finds the largest value in a set of data.
#
#
# VARIABLES: %rax holds the current value. %rdi holds the largest
# value. %rbx holds the current index. data_items is the
# actual set of data. The data is terminated with a 0.
#
.section .data
data_items:
.long 76, 38, 10, 93, 156, 19, 73, 84, 109, 12, 21, 0
.section .text
.globl _start
_start:
movq $0, %rbx
movq data_items(, %rbx, 4), %rax
movq %rax, %rdi
loop_start:
cmpq $0, %rax # Have we reached the end?
je loop_end
incq %rbx # Increment the index.
movq data_items(, %rbx, 4), %rax # Load the next value.
cmpq %rdi, %rax # Is new value larger?
jle loop_start
movq %rax, %rdi # New val is larger, store
# it.
jmp loop_start
loop_end:
# The largest value is already in %rdi and will be returned as
# exit status code.
movq $60, %rax
syscall