Bruno Moreira Guedes wrote:
> The mul(a,b) is replaced by a*b;
>
> But... Why executing that a milion of times is faster than using the
> simple a*b itself???
> It really happens? Why?
The best way to investigate this yourself would be to use gcc -S to generate the assembly listing for the mul(a,b) version and a*b version and see what's changed.
That said, I can't reproduce this - I get identical assembly produced from this test case (based on your snippet) whether I use the macro or not.
#include <iostream>
#define mul(X,Y) (X*Y)
int main(void)
{
int a,b,c;
std::cin >> a;
std::cin >> b;
c = mul(a,b);
std::cout << c << std::endl;
return 0;
}
And as far as I know and as far as I can see there's no 'mul' STL macro or template you're accidentally running into.
If you did intend to file a bug about this you'd need to tell us what CPU and OS you're using, what version of GCC this is and the command line you used - in particular which optimisation flags - and a complete, compilable test case.
Rup.
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