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有人可以帮我找出下列程序有什么问题吗?我正在阅读“从头开始编程”,并试图将这些示例翻译成x86-64汇编。以下程序将查找一组数据中的最大数字。但是当我组装,链接和运行时,我得到了0.显然这不是最大的数字。它使用32位寄存器/指令运行正常,但不是64位。汇编程序错误结果
# 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
好的,谢谢。我认为这可能是问题,但我不知道64位值的指令是什么。在这种情况下使用movq代替movl和.long值有没有什么好处? –