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* [Bug tree-optimization/108863] New: Unrolling could use range information
@ 2023-02-20 20:26 tkoenig at gcc dot gnu.org
2023-02-20 20:27 ` [Bug tree-optimization/108863] " tkoenig at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-02-20 20:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108863
Bug ID: 108863
Summary: Unrolling could use range information
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
Created attachment 54497
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54497&action=edit
Assembly code generated by test case
Looking a bit more at the code generated for the test code of PR108839.
For the test
$ cat u2.c
void foo(double *const restrict dx, double *dy, double da, long int n)
{
long int m = n % 4;
for (unsigned long i = 0; i < m; i++ )
dy[i] = dy[i] + da * dx[i];
}
a recently-ish trunk gives, with
$ gcc -S -O3 -funroll-all-loops -fno-tree-vectorize u2.c
far too much unrolling for a loop which can only be executed, at
most, four times (see attachment).
The range information about m does not appear to be propagated to
the unroll passes.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/108863] Unrolling could use range information
2023-02-20 20:26 [Bug tree-optimization/108863] New: Unrolling could use range information tkoenig at gcc dot gnu.org
@ 2023-02-20 20:27 ` tkoenig at gcc dot gnu.org
2023-02-20 20:33 ` [Bug rtl-optimization/108863] " pinskia at gcc dot gnu.org
2023-02-20 21:09 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-02-20 20:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108863
Thomas Koenig <tkoenig at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Keywords| |missed-optimization
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/108863] Unrolling could use range information
2023-02-20 20:26 [Bug tree-optimization/108863] New: Unrolling could use range information tkoenig at gcc dot gnu.org
2023-02-20 20:27 ` [Bug tree-optimization/108863] " tkoenig at gcc dot gnu.org
@ 2023-02-20 20:33 ` pinskia at gcc dot gnu.org
2023-02-20 21:09 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-20 20:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108863
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|tree-optimization |rtl-optimization
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Thomas Koenig from comment #0)
> The range information about m does not appear to be propagated to
> the unroll passes.
Most likely because range information is not propagated at all to rtl level.
In this case even just non-zero bits might be enough...
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/108863] Unrolling could use range information
2023-02-20 20:26 [Bug tree-optimization/108863] New: Unrolling could use range information tkoenig at gcc dot gnu.org
2023-02-20 20:27 ` [Bug tree-optimization/108863] " tkoenig at gcc dot gnu.org
2023-02-20 20:33 ` [Bug rtl-optimization/108863] " pinskia at gcc dot gnu.org
@ 2023-02-20 21:09 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-20 21:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108863
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-02-20
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. Though maybe the tree level unroller could improve this situtation
such that it just does the unroll here 4 times.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-02-20 21:09 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2023-02-20 20:26 [Bug tree-optimization/108863] New: Unrolling could use range information tkoenig at gcc dot gnu.org
2023-02-20 20:27 ` [Bug tree-optimization/108863] " tkoenig at gcc dot gnu.org
2023-02-20 20:33 ` [Bug rtl-optimization/108863] " pinskia at gcc dot gnu.org
2023-02-20 21:09 ` pinskia at gcc dot gnu.org
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