Thanks.
But with GCC 4.4.2, I get the dump in .lim file as
<bb 3>:
# a_14 = PHI <a_3(4), 0(2)>
b_lsm.36_1 = 10;
a_3 = a_14 + 1;
if (a_3 <= 99)
goto <bb 4>;
else
goto <bb 5>;
<bb 4>:
goto <bb 3>;
Clearly, b_lsm.36_1 = 10; is still in the loop.
Does this mean that loop invariant motion is not performed at all in gcc 4.4.2?
I am just confused as to why it isn't working in 4.4.2 version.
On Sun, Jan 3, 2010 at 7:31 PM, Tim Prince <n8tm@xxxxxxx> wrote:
> prashant rawat wrote:
>>
>> I have a simple C code :
>>
>> #include<stdio.h>
>> int *c;
>> int main ()
>> {
>> int a=0, b;
>> while (a < 100)
>> {
>> b = 10;
>> a = a + 1;
>> }
>> c = &b;
>> printf ("%d\n", *c);
>> return 0;
>> }
>>
>> I would basically expect the b = 10 statement to be moved out of the
>> while loop, as it is an invariant.
>> However, it does not seem to happen in the *.lim dump file.
>> I am using gcc 4.4.2 to compile, and the cmd line options are
>> install/bin/gcc -fdump-tree-all -O3 filename.c
>
> With gcc 4.5, the b assignment is moved out of the loop at -O, and the loop
> is removed entirely at -O3 or -Os.
>
--
With Regards,
Prashant SIngh Rawat
MTech, CSE, IIT Bombay
