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* [Bug tree-optimization/56352] New: Simplify testing of related conditions in for loop
@ 2013-02-15 22:36 josh.m.conner at gmail dot com
2021-08-07 23:17 ` [Bug tree-optimization/56352] " pinskia at gcc dot gnu.org
2021-08-07 23:30 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: josh.m.conner at gmail dot com @ 2013-02-15 22:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56352
Bug #: 56352
Summary: Simplify testing of related conditions in for loop
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: josh.m.conner@gmail.com
If we have a loop like this:
for (i = 0; i < a && i < b; i++)
{
/* Code which cannot affect i, a, or b */
}
gcc should be able to optimize this into:
tmp = MIN(a,b)
for (i = 0; i < tmp; i++)
{
/* Body */
}
But it does not. Similarly, code like:
for (i = 0; i < a; i++)
{
if (i >= b)
break;
/* Code which cannot affect i, a, or b */
}
Should be similarly optimized.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/56352] Simplify testing of related conditions in for loop
2013-02-15 22:36 [Bug tree-optimization/56352] New: Simplify testing of related conditions in for loop josh.m.conner at gmail dot com
@ 2021-08-07 23:17 ` pinskia at gcc dot gnu.org
2021-08-07 23:30 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-07 23:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56352
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Testcase:
int f(int);
void g(int a, int b)
{
int i;
for (i = 0; i < a; i++)
{
if (i >= b)
break;
f(i);
}
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/56352] Simplify testing of related conditions in for loop
2013-02-15 22:36 [Bug tree-optimization/56352] New: Simplify testing of related conditions in for loop josh.m.conner at gmail dot com
2021-08-07 23:17 ` [Bug tree-optimization/56352] " pinskia at gcc dot gnu.org
@ 2021-08-07 23:30 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-07 23:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56352
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |RESOLVED
Known to fail| |8.1.0, 8.5.0
Resolution|--- |DUPLICATE
Known to work| |10.1.0, 9.1.0, 9.4.0
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC9+ does the correct thing:
.L5:
movl %ebx, %edi
addl $1, %ebx
call f(int)
cmpl %ebx, %ebp
jg .L5
GCC 8.5 had:
_9 = b_5(D) <= i_7;
_8 = a_4(D) <= i_7;
_10 = _8 | _9;
This was fixed by r9-104.
Note there is some issues with mixing constants and non-constants but that is
still recorded in PR 85143.
And really this is a dup of bug 85143.
*** This bug has been marked as a duplicate of bug 85143 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-08-07 23:30 UTC | newest]
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2013-02-15 22:36 [Bug tree-optimization/56352] New: Simplify testing of related conditions in for loop josh.m.conner at gmail dot com
2021-08-07 23:17 ` [Bug tree-optimization/56352] " pinskia at gcc dot gnu.org
2021-08-07 23:30 ` pinskia at gcc dot gnu.org
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