https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34114
amker at gcc dot gnu.org changed:
What|Removed |Added
Status|NEW |RESOLVED
CC|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34114
--- Comment #8 from amker at gcc dot gnu.org ---
Author: amker
Date: Tue Aug 2 10:13:28 2016
New Revision: 238983
URL: https://gcc.gnu.org/viewcvs?rev=238983=gcc=rev
Log:
PR tree-optimization/34114
* tree-ssa-loop-niter.c
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34114
--- Comment #7 from amker at gcc dot gnu.org ---
Author: amker
Date: Tue Aug 2 10:09:33 2016
New Revision: 238982
URL: https://gcc.gnu.org/viewcvs?rev=238982=gcc=rev
Log:
PR tree-optimization/34114
* fold-const.c
--- Comment #1 from steven at gcc dot gnu dot org 2007-11-15 23:31 ---
We may be able to propagate somehow that rnd_to_2 is always even. I doubt it
is worth the trouble, to be honest... Zdenek may have some thought on this.
--
steven at gcc dot gnu dot org changed:
--- Comment #2 from lloyd at randombit dot net 2007-11-16 00:50 ---
Is there be any way to modify the code such that GCC would have an easier time
seeing this? I tried using 'assert(rnd_to_2 % 2 == 0)' (since glibc's
__assert_fail is marked with noreturn I thought it might help), but
--- Comment #4 from pinskia at gcc dot gnu dot org 2007-11-16 01:52 ---
(In reply to comment #3)
Here's another example, which I think may represent a different case (and
which
I found much more surprising than the first):
no_loop_opt2.c:5: warning: cannot optimize possibly
--- Comment #5 from lloyd at randombit dot net 2007-11-16 02:00 ---
Argh, you are correct. The original code has
unsigned int n = an_input / 160;
so this could never occur there, but GCC's inability to tell that this
assignment means that n cannot be UINT_MAX (in that code) is
--- Comment #3 from lloyd at randombit dot net 2007-11-16 01:49 ---
Here's another example, which I think may represent a different case (and which
I found much more surprising than the first):
$ cat no_loop_opt2.c
void g(unsigned int n)
{
unsigned int k;
for(k = 0; k = n;
--- Comment #6 from rakdver at gcc dot gnu dot org 2007-11-16 02:38 ---
(In reply to comment #2)
Is there be any way to modify the code such that GCC would have an easier time
seeing this? I tried using 'assert(rnd_to_2 % 2 == 0)' (since glibc's
__assert_fail is marked with noreturn
