使用 sse 内在函数时如何中断循环? [英] how to break from a loop when using sse intrinsics?
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问题描述
__m128* pSrc1 = (__m128*) string;
__m128 m0 = _mm_set_ps1(0); //null character
while(1)
{
__m128 result = __m128 _mm_cmpeq_ss(*pSrc1, m0);
//if character is \0 then break
//do some stuff here
pSrc1++;
}
我有一个字符串,其长度可以是 16 的倍数.如果 _mm_cmpeq_ss 返回相等,我该如何跳出循环?
I have a string whose length can be a multiple of 16. How do I break out of the loop if _mm_cmpeq_ss returns equal?
推荐答案
如果您在第一次遇到 \0
时试图跳出循环,那么您需要做一些事情像这样:
If you're trying to break out of the loop when you first encounter a \0
then you'll need to do something like this:
__m128i* pSrc1 = (__m128i *)string; // init pointer to start of string
__m128i m0 = _mm_set1_epi8(0); // vector of 16 `\0` characters
while (1)
{
__m128i v0 = _mm_loadu_si128(pSrc1); // get 16 chars from string
__m128i v1 = _mm_cmpeq_epi8(v0, m0); // compare all 16 chars with '\0'
int vmask = _mm_movemask_epi8(v1); // get 16 comparison result bits
if (vmask != 0) // if any bit is 1
break; // we found a `\0`, break out of loop
pSrc1++; // next 16 characters...
}
如果您只想测试某些位置的 \0
字符而忽略其他任何字符,那么您可以将 if (vmask != 0)
测试更改为符合您的特定要求.
If you only want to test for \0
characters in certain positions and ignore any others then you can change the if (vmask != 0)
test to something which matches your specific requirements.
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