Author: Dieter Buerssner
Date: 12:05:49 05/12/03
Go up one level in this thread
Typically, you need to define the functions first before you can inline them. So
(totally untested code)
#include <stdio.h>
int square(int x)
{
return x*x;
}
int main(void)
{
int i, sum = 0;
for (i=1; i < 10; i++)
sum += square(i);
printf("sum = %d\n", sum);
return 0;
}
Here most proabably, square will get inlined (when you use the right ompiler
options).
But in
#include <stdio.h>
int square(int);
int main(void)
{
int i, sum = 0;
for (i=1; i < 10; i++)
sum += square(i);
printf("sum = %d\n", sum);
return 0;
}
int square(int x)
{
return x*x;
}
Man compilers (all that I tried) will not be able to inline it.
BTW. For my code, typically letting inline the compiler as much as he can, will
yield in slower code on x86 hardware. Typically functions are a bit more
complicated than square(). The compiler must do compromises, especially on
platforms with relatively few free registers available. When the compilere
inlines, he may make a decision to keep some vars of the caller in registers,
that the callee has not available now, and makes it slower by this.
I think, it is no coincidence, that compilers do not default typically to inline
functions. If it allways would be better, they would default for this.
Regards,
Dieter
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