[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #13 from bonzini at gnu dot org 2009-01-28 11:50 --- Aren't loads protected by the gimple_set_has_volatile_ops anyway? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #14 from rguenther at suse dot de 2009-01-28 12:08 --- Subject: Re: [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address On Wed, 28 Jan 2009, bonzini at gnu dot org wrote: --- Comment #13 from bonzini at gnu dot org 2009-01-28 11:50 --- Aren't loads protected by the gimple_set_has_volatile_ops anyway? No, only during early optimizations (because we don't have virtual operands there). Richard. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
-- rguenth at gcc dot gnu dot org changed: What|Removed |Added Priority|P3 |P2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #1 from pinskia at gmail dot com 2009-01-27 11:27 ---
Subject: Re: New: [4.2/4.3/4.4 Regression] missing constraints for pointers
accessed directly via their address
Sent from my iPhone
On Jan 27, 2009, at 3:15 AM, bonzini at gnu dot org gcc-bugzi...@gcc.gnu.org
wrote:
This testcase fails:
/* { dg-do compile } */
/* { dg-options -O2 -fdump-tree-optimized } */
int f(int *p)
{
int a = *p;
int *q = (int *)0xDEADBEE0;
*q = 5;
return *p == a;
}
/* { dg-final { scan-tree-dump-times = \\\*p 2 optimized } } */
/* { dg-final { scan-tree-dump-not return 1 optimized } } */
/* { dg-final { cleanup-tree-dump optimized } } */
Unlike PR38984 it does not require -fno-delete-null-pointer-checks.
Volatile addresses also don't have vops on them. As I mentioned in
the other bug. So this is also a bug for volatiles.
--
Summary: [4.2/4.3/4.4 Regression] missing constraints for
pointers accessed directly via their address
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bonzini at gnu dot org
OtherBugsDependingO 38984
nThis:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #2 from rguenth at gcc dot gnu dot org 2009-01-27 12:04 --- Works on the alias-improvements branch. Confirmed. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Known to fail|4.1.3 4.4.0 |4.0.4 4.1.3 4.4.0 Last reconfirmed|-00-00 00:00:00 |2009-01-27 12:04:37 date|| Target Milestone|--- |4.2.5 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #4 from rguenth at gcc dot gnu dot org 2009-01-27 12:06 ---
In the operand scanner we try to be clever ...
else if (TREE_CODE (ptr) == INTEGER_CST)
{
/* If a constant is used as a pointer, we can't generate a real
operand for it but we mark the statement volatile to prevent
optimizations from messing things up. */
gimple_set_has_volatile_ops (stmt, true);
return;
but that of course misses the fact that we miss all necessary conflicts.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #5 from rguenth at gcc dot gnu dot org 2009-01-27 12:09 --- The bad thing is that this is really bad. We would need to add the SMT for the type here, but we have no way of looking that up. So the only way to fix this in a reasonable way is to simply not CCP constant addresses into dereferences. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #6 from bonzini at gnu dot org 2009-01-27 12:21 --- These passes are able to propagate the address to the load: CCP, VRP, DOM. If we decide that it's an invalid transformation, fixing them would fix this bug. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #3 from rguenth at gcc dot gnu dot org 2009-01-27 12:04 --- Mine. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot |dot org |org Status|NEW |ASSIGNED Last reconfirmed|2009-01-27 12:04:37 |2009-01-27 12:04:54 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #7 from bonzini at gnu dot org 2009-01-27 12:29 --- simply not CCP constant addresses into dereferences. Apart from the fact that it's not only CCP, it seems mostly sensible. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #8 from rguenth at gcc dot gnu dot org 2009-01-27 12:31 --- Created an attachment (id=17190) -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17190action=view) incomplete patch I tried this quick hack to add proper operands for the dereference, but it shows that (of course) we do not bother to create SMTs for dereferences of constants. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #9 from rguenth at gcc dot gnu dot org 2009-01-27 12:33 --- As this bug exists basically forever (since tree-ssa merge) I am inclined to only fix it for 4.5 with the alias-improvements branch merge. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #10 from bonzini at gnu dot org 2009-01-27 12:58 --- Created an attachment (id=17191) -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17191action=view) tentative patch Do you want to pursue something as in the attached patch instead? You can then revert it in the alias-improvements branch if you wish. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #11 from rguenth at gcc dot gnu dot org 2009-01-27 13:05 --- The patch is not enough. Consider replacements in loads and in loads of call arguments to const/pure calls. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
[Bug tree-optimization/38985] [4.2/4.3/4.4 Regression] missing constraints for pointers accessed directly via their address
--- Comment #12 from bonzini at gnu dot org 2009-01-27 13:18 --- Ok, I'm not working on it anyway. I'll just leave the patch in case someone else would pick it up. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38985
