[Bug middle-end/36902] Array bound warning with dead code after optimization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902 Andrew Pinski changed: What|Removed |Added Known to fail|| Known to work|| Target Milestone|--- |4.5.0
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #34 from manu at gcc dot gnu dot org 2009-04-18 09:25 --- Subject: Bug 36902 Author: manu Date: Sat Apr 18 09:24:45 2009 New Revision: 146305 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=146305 Log: 2009-04-18 Manuel López-Ibáñez m...@gcc.gnu.org PR middle-end/36902 * tree-vrp.c (check_array_ref): Pass a location_t instead of a pointer. Use warning_at instead of warning. (search_for_addr_array): Likewise. (check_array_bounds): Likewise. (check_all_array_refs): Check that the incoming edge is not in the list of edges to be removed. (check_all_array_refs): Avoid the temporal pointer. (vrp_visit_cond_stmt): Fix typo. (simplify_switch_using_ranges): Handle the case where the switch index is an integer constant. testsuite/ * gcc.dg/pr36902.c: New. Added: trunk/gcc/testsuite/gcc.dg/pr36902.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-vrp.c -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #35 from manu at gcc dot gnu dot org 2009-04-18 09:29 --- FIXED in GCC 4.5 -- manu at gcc dot gnu dot org changed: What|Removed |Added OtherBugsDependingO|37921 | nThis|| Status|NEW |RESOLVED Resolution||FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #27 from paolo dot carlini at oracle dot com 2008-11-18 10:16 --- Isn't this a regression? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #28 from hjl dot tools at gmail dot com 2008-11-18 14:42 --- (In reply to comment #27) Isn't this a regression? The warning is new. But the same code won't compile with -Wall while gcc 4.1 has no problems. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #29 from manu at gcc dot gnu dot org 2008-11-18 15:21 --- There is a patch here: http://gcc.gnu.org/ml/gcc-patches/2008-10/msg01117.html -- manu at gcc dot gnu dot org changed: What|Removed |Added Last reconfirmed|2008-07-22 21:18:28 |2008-11-18 15:21:32 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #30 from paolo dot carlini at oracle dot com 2008-11-18 15:25 --- Thanks Manuel. I'm not sure that this is technically a regression, but in any case I consider it a serious problem and really hope we can have a fix for 4.4.0. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #31 from manu at gcc dot gnu dot org 2008-11-18 15:43 --- (In reply to comment #30) Thanks Manuel. I'm not sure that this is technically a regression, but in any case I consider it a serious problem and really hope we can have a fix for 4.4.0. I submitted the patch long ago. We are in regressions-only mode. This is not a regression. Not sure what else you want me to do. (It doesn't fix PR37921, though. I haven't tested PR35392.) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #32 from paolo dot carlini at oracle dot com 2008-11-18 15:47 --- (In reply to comment #31) I submitted the patch long ago. We are in regressions-only mode. This is not a regression. Not sure what else you want me to do. I'm not sure either ;) Maybe you could just work on the complete solution (per your posted scheme), fixing also the other known issues in this area, and submit it again for mainline after we branched... -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #33 from manu at gcc dot gnu dot org 2008-11-18 16:05 --- (In reply to comment #32) (In reply to comment #31) I submitted the patch long ago. We are in regressions-only mode. This is not a regression. Not sure what else you want me to do. I'm not sure either ;) Maybe you could just work on the complete solution (per your posted scheme), fixing also the other known issues in this area, and submit it again for mainline after we branched... Or maybe I can just wait until this patch is reviewed, so I can get the official answer to my approach before wasting my free time foolishly in a futile endeavour. ;-) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #26 from pinskia at gcc dot gnu dot org 2008-11-15 00:07 --- *** Bug 35392 has been marked as a duplicate of this bug. *** -- pinskia at gcc dot gnu dot org changed: What|Removed |Added CC||etienne_lorrain at yahoo dot ||fr http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #24 from hjl dot tools at gmail dot com 2008-10-26 22:06 --- *** Bug 37921 has been marked as a duplicate of this bug. *** -- hjl dot tools at gmail dot com changed: What|Removed |Added CC||arjan at linux dot intel dot ||com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #25 from pinskia at gcc dot gnu dot org 2008-10-27 00:17 --- *** Bug 37921 has been marked as a duplicate of this bug. *** -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #22 from mueller at gcc dot gnu dot org 2008-08-25 07:59 --- there is currently no good way to detect if a block is dead during the VRP pass, as the VRP information is used for *determining* wether or not a block is dead. Is there a general warning-queuing implementation that I could make use of or is there some other warning that does that already? Iirc the is used/ might be used uninitialized type of warnings do not use something like that. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #23 from manu at gcc dot gnu dot org 2008-08-25 10:50 --- (In reply to comment #22) there is currently no good way to detect if a block is dead during the VRP pass, as the VRP information is used for *determining* wether or not a block is dead. I think in this case it is. simplify_switch_using_ranges is called before the warning occurs. However, it doesn't handle the case where the switch index is an integer constant! So it just doesn't do anything. I think this is a missed optimization, it should simplify the switch. Is there a general warning-queuing implementation that I could make use of or is there some other warning that does that already? Iirc the is used/ might be used uninitialized type of warnings do not use something like that. No, we don't have that but is used/ may be used does detect whether the current BB is always executed or not. That would be an improvement in my opinion. Not in this case anyway because as I said above, in this case we could do perfect. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #17 from manu at gcc dot gnu dot org 2008-08-22 16:44 ---
The location passed to check_array_ref is correct but the new way to check if
we are in system headers does not work well with the %H hack. This will go away
soon hopefully when everything takes an explicit location. The fix is to use
warning_at. This kind of thing may happen in the middle-end and in the
front-end. This doesn't fix the bogus warning though, it just suppresses it
within system headers.
Index: gcc/tree-vrp.c
===
--- gcc/tree-vrp.c (revision 139373)
+++ gcc/tree-vrp.c (working copy)
@@ -4811,11 +4811,11 @@ insert_range_assertions (void)
range. If the array subscript is a RANGE, warn if it is
non-overlapping with valid range.
IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside a ADDR_EXPR. */
static void
-check_array_ref (tree ref, const location_t *location, bool ignore_off_by_one)
+check_array_ref (tree ref, location_t location, bool ignore_off_by_one)
{
value_range_t* vr = NULL;
tree low_sub, up_sub;
tree low_bound, up_bound = array_ref_up_bound (ref);
@@ -4850,12 +4850,12 @@ check_array_ref (tree ref, const locatio
if (TREE_CODE (up_sub) == INTEGER_CST
tree_int_cst_lt (up_bound, up_sub)
TREE_CODE (low_sub) == INTEGER_CST
tree_int_cst_lt (low_sub, low_bound))
{
- warning (OPT_Warray_bounds,
- %Harray subscript is outside array bounds, location);
+ warning_at (location, OPT_Warray_bounds,
+ array subscript is outside array bounds);
TREE_NO_WARNING (ref) = 1;
}
}
else if (TREE_CODE (up_sub) == INTEGER_CST
tree_int_cst_lt (up_bound, up_sub)
@@ -4865,28 +4865,28 @@ check_array_ref (tree ref, const locatio
up_bound,
integer_one_node,
0),
up_sub)))
{
- warning (OPT_Warray_bounds, %Harray subscript is above array bounds,
- location);
+ warning_at (location, OPT_Warray_bounds,
+ array subscript is above array bounds);
TREE_NO_WARNING (ref) = 1;
}
else if (TREE_CODE (low_sub) == INTEGER_CST
tree_int_cst_lt (low_sub, low_bound))
{
- warning (OPT_Warray_bounds, %Harray subscript is below array bounds,
- location);
+ warning_at (location, OPT_Warray_bounds,
+ array subscript is below array bounds);
TREE_NO_WARNING (ref) = 1;
}
}
/* Searches if the expr T, located at LOCATION computes
address of an ARRAY_REF, and call check_array_ref on it. */
static void
-search_for_addr_array(tree t, const location_t *location)
+search_for_addr_array(tree t, location_t location)
{
while (TREE_CODE (t) == SSA_NAME)
{
gimple g = SSA_NAME_DEF_STMT (t);
@@ -4925,11 +4925,11 @@ search_for_addr_array(tree t, const loca
static tree
check_array_bounds (tree *tp, int *walk_subtree, void *data)
{
tree t = *tp;
struct walk_stmt_info *wi = (struct walk_stmt_info *) data;
- const location_t *location = (const location_t *) wi-info;
+ location_t location = *((location_t *) wi-info);
*walk_subtree = TRUE;
if (TREE_CODE (t) == ARRAY_REF)
check_array_ref (t, location, false /*ignore_off_by_one*/);
@@ -4972,11 +4972,11 @@ check_all_array_refs (void)
continue;
}
for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (si))
{
gimple stmt = gsi_stmt (si);
- const location_t *location = gimple_location_ptr (stmt);
+ location_t location = gimple_location (stmt);
struct walk_stmt_info wi;
if (!gimple_has_location (stmt))
continue;
if (is_gimple_call (stmt))
@@ -4990,12 +4990,12 @@ check_all_array_refs (void)
}
}
else
{
memset (wi, 0, sizeof (wi));
- wi.info = CONST_CAST (void *, (const void *) location);
-
+ /* wi.info = CONST_CAST (void *, (const void *)
location);*/
+ wi.info = (void *) location;
walk_gimple_op (gsi_stmt (si),
check_array_bounds,
wi);
}
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #18 from manu at gcc dot gnu dot org 2008-08-22 17:04 --- (In reply to comment #1) This happens because the warning happens very early in the compiler so it does not know that the case5 is not going to be used. I think the warning is correct and not really bogus if you take that into account. I think that if the compiler knows that the code is never executed then, we shouldn't warn. Anyway, this could be seen as a request enhancement. BTW, the offending code is removed within the first vrp pass, so perhaps we are not properly detecting that the BB is unreachable. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #19 from pinskia at gcc dot gnu dot org 2008-08-22 17:30 --- (In reply to comment #18) I think that if the compiler knows that the code is never executed then, we shouldn't warn. It does but only later on in the optimization it knows that the code is dead. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #20 from hjl dot tools at gmail dot com 2008-08-22 17:37 --- (In reply to comment #19) (In reply to comment #18) I think that if the compiler knows that the code is never executed then, we shouldn't warn. It does but only later on in the optimization it knows that the code is dead. Why can't we queue those warnings which may come from dead code and suppress them if they are dead? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #21 from manu at gcc dot gnu dot org 2008-08-22 17:54 --- (In reply to comment #19) (In reply to comment #18) I think that if the compiler knows that the code is never executed then, we shouldn't warn. It does but only later on in the optimization it knows that the code is dead. My point is that if I understand the vrp code correctly, we can detect that the code is dead before warning. In this case, the code is detected dead within VRP, not in a later pass. Maybe I am wrong. Let's see what Mueller and Guenther have to say. In any case, we should consider whether warning in conditional BBs is a good idea at all. I think that saying array subscript *is* above array bounds in a BB that is executed conditionally is not a good idea in general. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #14 from manu at gcc dot gnu dot org 2008-08-15 20:11 --- (In reply to comment #13) You see, as I feared: this class of warnings coming from the middle-end is especially nasty, because cannot be suppressed by any normal means. What location is being passed to that warning? -- manu at gcc dot gnu dot org changed: What|Removed |Added CC||manu at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #15 from manu at gcc dot gnu dot org 2008-08-15 20:18 --- GCC system_headers should suppress this warning now, doesn't it? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #16 from paolo dot carlini at oracle dot com 2008-08-15 20:36 --- No news, Manuel, still unsuppressed by the pragma -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #3 from pinskia at gcc dot gnu dot org 2008-07-22 21:18 --- The warning is very fragile: if the buffer in main() is not static then there is no failure; is the size is passed as a constant there is no error. Not really, if you read my comment, you will understand why this is not that fragile after all. I can make it even worse if you do a couple of things to trick one optimization pass up enough so we warn in the first VRP but don't optimize it away until the last VRP pass. But really this is the normal issue with optimizers warnings and is a hard problem to solve in general and I don't think we can count this as a regression really. -- pinskia at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Keywords||diagnostic Last reconfirmed|-00-00 00:00:00 |2008-07-22 21:18:28 date|| Summary|[4.3/4.4 Regression]: Bogus |Array bound warning with |array bound warning |dead code after optimization http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #4 from paolo dot carlini at oracle dot com 2008-07-22 21:26 --- Out of curiosity: if this kind of code appears in a system header, is #pragma GCC system_header able to suppress the warning? Of course I'm asking because this is the most annoying feature of PR 36633 (which immediately came to my mind when I saw this one ;) -- paolo dot carlini at oracle dot com changed: What|Removed |Added CC||paolo at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #5 from hjl dot tools at gmail dot com 2008-07-22 21:29 --- It is a regression since the same correct code no longer compiles with -Werror -Wall after upgrading from gcc 4.1/4.2 to 4.3. -- hjl dot tools at gmail dot com changed: What|Removed |Added Known to fail||4.3.1 4.4.0 Known to work||4.1.3 4.2.5 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #6 from hjl dot tools at gmail dot com 2008-07-22 21:30 --- (In reply to comment #4) Out of curiosity: if this kind of code appears in a system header, is #pragma GCC system_header able to suppress the warning? Of course I'm asking because this is the most annoying feature of PR 36633 (which immediately came to my mind when I saw this one ;) It comes from an application. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #7 from paolo dot carlini at oracle dot com 2008-07-22 21:32 --- (In reply to comment #6) It comes from an application. This doesn't answer my question. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #8 from hjl dot tools at gmail dot com 2008-07-22 21:42 --- (In reply to comment #7) (In reply to comment #6) It comes from an application. This doesn't answer my question. I said It comes from an application. It isn't from system header file. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #9 from paolo dot carlini at oracle dot com 2008-07-22 22:53 --- I said It comes from an application. It isn't from system header file. Yes, and that doesn't answer my question. I asked if the pragma is able to suppress a warning triggered by your kind of snippet, IF, when, it appears in an header file: I asked about an HYPOTHETICAL situation, not your actual situation. Is that more clear? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #10 from hjl dot tools at gmail dot com 2008-07-23 01:04
---
(In reply to comment #9)
I said It comes from an application. It isn't from system header file.
Yes, and that doesn't answer my question. I asked if the pragma is able to
suppress a warning triggered by your kind of snippet, IF, when, it appears in
an header file: I asked about an HYPOTHETICAL situation, not your actual
situation. Is that more clear?
It doesn't make a difference:
[EMAIL PROTECTED] tmp]$ cat y.h
#pragma GCC system_header
static inline unsigned char *
foo(unsigned char * to, const unsigned char * from, int n)
{
switch ( n )
{
case 3:
*to = *from;
break;
case 5:
to[4] = from [4];
break;
}
return to;
}
[EMAIL PROTECTED] tmp]$ cat y.c
#include y.h
struct {
intsize_of_select;
unsigned char pcr_select[4];
} sel;
int main(int argc, char *argv[])
{
static unsigned char buf[64];
sel.size_of_select = 3;
foo(buf, sel.pcr_select, sel.size_of_select);
return 1;
}
[EMAIL PROTECTED] tmp]$ gcc -Wall -O2 -c y.c -Werror -I.
cc1: warnings being treated as errors
y.c: In function âmainâ:
./y.h:11: error: array subscript is above array bounds
[EMAIL PROTECTED] tmp]$
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #11 from paolo dot carlini at oracle dot com 2008-07-23 01:16 --- Thanks. Actually, I think the experiment would be more meaningful if you could put also the equivalent of your main (a calling function, that is) inside the header, because in your testcase the warning is triggered inside the main, not in foo. If you can, in your spare time, of course. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #12 from hjl dot tools at gmail dot com 2008-07-23 01:23
---
(In reply to comment #11)
Thanks. Actually, I think the experiment would be more meaningful if you could
put also the equivalent of your main (a calling function, that is) inside the
header, because in your testcase the warning is triggered inside the main, not
in foo.
Same:
[EMAIL PROTECTED] tmp]$ cat y.h
#pragma GCC system_header
static inline unsigned char *
foo(unsigned char * to, const unsigned char * from, int n)
{
switch ( n )
{
case 3:
*to = *from;
break;
case 5:
to[4] = from [4];
break;
}
return to;
}
struct {
intsize_of_select;
unsigned char pcr_select[4];
} sel;
static int
bar (void)
{
static unsigned char buf[64];
sel.size_of_select = 3;
foo(buf, sel.pcr_select, sel.size_of_select);
return 1;
}
[EMAIL PROTECTED] tmp]$ cat y.c
#include y.h
int
main ()
{
return bar ();
}
[EMAIL PROTECTED] tmp]$ gcc -Wall -O2 -c y.c -Werror -I.
cc1: warnings being treated as errors
y.c: In function âmainâ:
./y.h:11: error: array subscript is above array bounds
[EMAIL PROTECTED] tmp]$
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
[Bug middle-end/36902] Array bound warning with dead code after optimization
--- Comment #13 from paolo dot carlini at oracle dot com 2008-07-23 01:28 --- You see, as I feared: this class of warnings coming from the middle-end is especially nasty, because cannot be suppressed by any normal means. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36902
