[英]The program crashes when running strlen() written in assembly with SSE4.2 instructions
My program is below and I want to use it to calculate the length of a string. 我的程序在下面,我想用它来计算字符串的长度。
.CODE
EQUAL_EACH = 1000b
strlen_sse PROC
string equ [esp+4]
mov ecx, string
;ecx = string
mov eax, -16
mov edx, ecx
pxor xmm0, xmm0
STRLEN_LOOP:
add eax, 16
PcmpIstrI xmm0, xmmword ptr [edx+eax], EQUAL_EACH
jnz STRLEN_LOOP
add eax, ecx
ret
strlen_sse ENDP
END
It always crashes when I run it. 当我运行它时,它总是崩溃。 What caused this? 是什么原因造成的?
The main
is like below: main
内容如下:
#include<stdio.h>
#include<windows.h>
extern "C" int strlen_sse(const char* src);
int main(){
DWORD start,stop;
char* str = "asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf";
start = GetTickCount();
for (; i < 100000000; i++) {
strlen_sse(str);
}
stop = GetTickCount();
printf("%lld ms\n",stop-start);
}
My working environment is visual studio 2015 community
, the platform of the project is x64(active)
, there is not any errors when I compile it. 我的工作环境是visual studio 2015 community
,项目的平台是x64(active)
,编译时没有任何错误。
How can I fix this bug? 如何解决此错误?
The C code is probably compiled to 64bit code, and the assembly is 32 bit code. C代码可能已编译为64位代码,而汇编则为32位代码。 Having 32 bit code in a 64 bit code segment will not work. 在64位代码段中包含32位代码将不起作用。
Change the assembly to this (I removed unnecessary code aswell): 将程序集更改为此(我也删除了不必要的代码):
.CODE
EQUAL_EACH = 1000b
strlen_sse PROC
mov rax, -16
mov rdx, [rsp + 8]
pxor xmm0, xmm0
STRLEN_LOOP:
add rax, 16
PcmpIstrI xmm0, xmmword ptr [rdx+rax], EQUAL_EACH
jnz STRLEN_LOOP
add rax, rcx
ret
strlen_sse ENDP
END
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