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* [Bug tree-optimization/68548] bogus "may be used uninitialized" (predicate analysis)
[not found] <bug-68548-4@http.gcc.gnu.org/bugzilla/>
@ 2021-03-31 20:37 ` msebor at gcc dot gnu.org
2024-03-16 23:48 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: msebor at gcc dot gnu.org @ 2021-03-31 20:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68548
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |msebor at gcc dot gnu.org
Known to fail|4.9.3, 5.2.0 |10.2.0, 11.0, 4.9.4, 5.5.0,
| |6.4.0, 7.2.0, 8.3.0, 9.1.0
--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Reconfirmed with GCC 11. It's not a regression. With a patch I'm working with
GCC issues the following warning and notes confirming the analysis from comment
#1 and #2.
pr68548.c: In function ‘foo’:
pr68548.c:14:17: warning: ‘data0’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
14 | bar(data0);
| ^~~~~~~~~~
pr68548.c:7:18: note: when ‘(writemask & 1) == 0’
7 | unsigned data0;
| ^~~~~
pr68548.c:7:18: note: used when ‘(writemask & 1) == 0’
pr68548.c:7:18: note: ‘data0’ was declared here
EVRP knows to fold the test for data0 != data to false but nothing substitutes
data for data0 when the value is passed to another function or returned. So
the following, for instance, doesn't trigger a warning because the data0 - data
subtraction is folded into zero.
int x;
void baz (unsigned writemask, unsigned data) {
unsigned remaining = X;
unsigned data0;
if (writemask & X) data0 = data;
remaining &= ~writemask;
if (remaining == 0)
x = data0 - data;
}
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/68548] bogus "may be used uninitialized" (predicate analysis)
[not found] <bug-68548-4@http.gcc.gnu.org/bugzilla/>
2021-03-31 20:37 ` [Bug tree-optimization/68548] bogus "may be used uninitialized" (predicate analysis) msebor at gcc dot gnu.org
@ 2024-03-16 23:48 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-03-16 23:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68548
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Keywords| |missed-optimization
Target Milestone|--- |14.0
Resolution|--- |FIXED
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed on the trunk. A jump threading improvement fixed it.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-03-31 20:37 ` [Bug tree-optimization/68548] bogus "may be used uninitialized" (predicate analysis) msebor at gcc dot gnu.org
2024-03-16 23:48 ` pinskia at gcc dot gnu.org
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