Re: Code generator detail

Bartc wrote:
OK

1: I changed the code generator to emit the code as you want
2: I wrote this program:

typedef void (*fnptr)(void);
fnptr pfnptr;
fnptr *ppfnptr;
void n(void)
{
}

int main(void)
{
	int i;

	pfnptr=n;
	ppfnptr = &pfnptr;
	for (i=0; i<100000000; i++)
		(*ppfnptr)();
}

Then I compiled using the new code generator. Elapsed time 1.558 seconds
Then I compiled using the old code generator. Elapsed time 1.502 seconds

The difference is not significative

Code generated by the old code generator:
[0000027] 8b1d00000000     mov       0x0,%ebx   (_ppfnptr)
[0000033] ff141d00000000   call      *0x0(,%ebx,1)

Code generated by the new code generator:
[0000027] 8b1d00000000     mov       0x0,%ebx   (_ppfnptr)
[0000033] 8b1b             mov       (%ebx),%ebx
[0000035] ffd3             call      *%ebx

I would like to improve the code generated, but I just do not understand
why you see such a difference.

Which CPU are you using?
Which OS?


-- 
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique
http://www.cs.virginia.edu/~lcc-win32