This is the mail archive of the
gcc-help@gcc.gnu.org
mailing list for the GCC project.
Re: Which pass optimizes if (x != x + 10) to if (1)?
On 03/21/2012 07:00 AM, Zhenqiang Chen wrote:
> Thank you for the comment. I found the root cause. In function
> tree_swap_operands_p (fold-const.c), there is a check
>
> if (optimize_function_for_size_p (cfun))
> return 0;
>
> which blocks to swap (x != x + 10) to (x + 10 != x). And the following
> optimization can only handle (x + 10 != x).
>
> In most cases, constant-folding will benefit for code size. Any reason
> to add this check?
If you search the history you'll probably find a bug that was
fixed by this (admittedly rather odd) test.
Andrew.