送交者: AQuestion 于 2005-6-30, 18:58:28:

The following code will not run correctly if
compiled with gcc -O2. It is ok without any optimization
or -O3. What is wrong. My inline asm knowledge
is very limited (from google), maybe there is something
wrong there?

#include

void test(int num)
{
int i;

__asm__ __volatile__(
"1:"
"dec %%ecx \n\t"
"jnz 1b \n\t"
:
: "c" (num>>4)
: "memory"
);

for(i=(num>>4)<<4; i printf("OK i=%d\n", i);
}

main()
{
test(35);
}

• Well, nothing is really wrong - wasguru (365 bytes) 2005-6-30, 23:35:15
  • Oops... - wasguru (544 bytes) 2005-6-30, 23:40:03
    • Is this a bug of GCC or what? - AQuestion (221 bytes) 2005-7-01, 00:42:44
      • No, there is no way for gcc to figure out "num4" has been changed - AA (137 bytes) 2005-7-01, 02:56:29
• again - AQuestion (378 bytes) 2005-6-30, 19:10:11

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